Battery parallelization for power tools

Abstract

A battery interface unit, BIU, (110) for a powertool (100), the BIU (110) comprising at least one control unit, two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit, where each interface circuit is associated with a closed configuration and an open configuration, where the respective battery interface port (210) is connected to the output port (220) in the closed configuration and where electric current is allowed to flow from the battery interface port (210) to the output port (220) and not from the output port (220) to the battery interface port (210) in the open configuration, where each interface circuit is arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port (210) and the output port (220) satisfies an acceptance criterion.

Description

[0001] TITLE

[0002] BATTERY PARALLELIZATION FOR POWER TOOLS

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to battery parallelization, i.e., the concurrent use of more than one battery to power an electric device such as a powertool.

[0005] BACKGROUND

[0006] Some cordless power tools, such as leaf blowers, chainsaws, powercutters, concrete vibrators, and surface compactors, require a large amount of electrical energy to operate. At the same time, the energy capacity of a single battery unit may be limited due to restrictions on, e.g., size, weight, and battery unit cost. Thus, more than one battery unit may be required to provide sufficient energy.

[0007] By using two or more smaller batteries instead of a larger battery to power a device with high energy demand, lighter more manageable batteries can be used. The smaller batteries can also be used as stand-alone power sources in other types of devices that do not have the same energy requirements, which results in a more versatile battery system that supports a wider range of different powertools.

[0008] A battery parallelization circuit is a circuit which connects two or more batteries to an electric power consumer such as a motor. Various types of battery parallelization solutions are known. For instance, sequential battery discharging solutions that discharge batteries one by one in sequence, and complex DC / DC converter-based solutions that balance the currents drawn from two or more batteries.

[0009] A problem associated with some battery parallelization circuits is that electric current may flow in an uncontrolled manner from a battery with high charge to a battery with lower charge, instead of to the intended power consumer. EP4235905 A1 and US20190160972 A1 show example battery parallelization circuits which control the direction of current to and from the connected batteries.

[0010] AU2017101729 A4 relates to a battery interface unit with diodes that control electrical connections between batteries connected in parallel and a load.

[0011] US5399908 describes a system for sharing losses of parallel transistors.

[0012] However, improvements and / or alternatives are desired.

[0013] Safety is always a concern when it comes to powertools, in particular when high energy density batteries are part of the powertool.

[0014] SUMMARY

[0015] It is an objective of the present disclosure to provide improved or at least alternative battery parallelization solutions for powertools such as leaf blowers, concrete vibrators, chainsaws, and powercutters. This objective is at least in part obtained by a battery interface unit (BIU) according to the appended claims.

[0016] According to example aspects, the BIU comprises at least one control unit, two or more battery interface ports for connecting respective battery units, and at least one output port for connecting a power consumer of the powertool to the BIU. Each battery interface port is connected to the output port via at least one transistor-based interface circuit. Each such interface circuit is associated with a closed configuration and an open configuration. In the closed configuration the respective battery interface port is connected to the output port such that electric current can flow back and forth between the battery interface port and the output port. In the open configuration electric current is allowed to flow from the battery interface port to the output port, but not in reverse from the output port to the battery interface port. Each interface circuit is arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port and the output port satisfies an acceptance criterion. The BIU preferably also comprises a powersink circuit connected to the output port. This powersink circuit comprises a resistive load and a powersink control unit arranged to connect the load to the output port in order to dissipate excess electrical energy at the output port. The powersink control unit may be a separate control circuit or form part of a more general control unit of the BIU. This way an unwanted excess of electrical energy in the system can be avoided in a robust and cost efficient manner. By adding a powersink circuit to the BIU, potential complexity reductions in the other parts of the powertool electrical system are enabled, which is an advantage.

[0017] The closed configuration of the interface circuit may be referred to as an ON- state, while the open configuration of the interface circuit may be referred to as an OFF-state.

[0018] By means of the different BIUs disclosed herein, it becomes possible to efficiently and robustly discharge a set of batteries in parallel, without a complex DC / DC battery interface architecture and without advanced software functions executing on digital processing circuitry.

[0019] The BIU allows an increase of the total amount of electrical energy available to a power tool without increasing the weight, size, or cost of the individual battery units. The overall energy efficiency of the batteries connected to the BIU is also increased due to current sharing among connected batteries.

[0020] The heat generation in the batteries is lowered, which results in decreased cooling needs and normally also in decreased battery unit wear.

[0021] The BIUs discussed herein allow for continuous operation of the powertool, as opposed to sequential discharge systems which may require a brief stop of the powertool operation while switching from one active battery unit to another.

[0022] Some of the BIU designs presented herein operate without complex software executing on digital processing circuitry, or even entirely without software, which may result in an increased robustness and reduced complexity. In other words, the control functionality implemented by the control unit of at least some of the BIUs disclosed herein is realized by analog control circuitry, which is an advantage in at least some use cases. The acceptance criterion may according to an example be considered as satisfied if a difference in voltage of the respective battery interface port and a voltage of the output port lies within a predetermined range, such as when the voltage of the respective battery interface port exceeds the voltage of the output port. This way reverse currents flowing back into the battery units are prevented. A margin in the voltage difference may be required in order to account for voltage drop caused by a load on a battery unit. The margin may be configured by the system in dependence of the type of battery connected to a given battery interface port. The acceptance criterion may involve a preconfigured offset voltage, such that the difference in voltage of the respective battery interface port and the voltage of the output port must exceed a positive threshold value, such as 0,1 % of a nominal voltage of the battery units.

[0023] It is appreciated that the transistor-based interface circuits described herein may comprise one, two or more transistors. According to some aspects, at least one of the transistor-based interface circuits comprises two or more transistors connected in parallel between the battery interface port and the output port. This way losses are reduced, and the transistor-based interface circuits may together conduct a higher magnitude current.

[0024] According to some other aspects, at least one of the transistor-based interface circuits comprises a metal-oxide-semiconductor field-effect transistor (MOSFET) with an intrinsic diode, also known as a body diode, arranged to prevent electric current in direction from the output port towards the battery interface port, and to conduct current in the opposite direction from the battery interface port towards the output port. MOSFET transistors are relatively low cost components that provide high switching speed, low power consumption, and ability to handle significant current. Each interface circuit optionally comprises a respective comparator function arranged to determine the voltage difference between the battery interface port and the output port and to generate a control signal indicative of the voltage difference. The respective interface circuit can then be arranged to automatically transition into its respective closed configuration in dependence of a state of the control signal. This way no software is required for the transitioning functionality of the transistor-based interface circuits, which is an advantage since a particularly robust design solution is obtained at reasonable design complexity. It is a further advantage that the intrinsic diode conducts in direction from the battery interface port towards the output port, since then some feed current can be provided from a battery unit even if the automatic transition of the interface circuit into its closed configuration fails for some reason.

[0025] According to some other aspects, each battery interface port is connected to the output port via a respective port enabling circuit that is associated with an enabled configuration and a disabled configuration. Each such port enabling circuit is arranged to prevent or allow electric current in direction from the battery interface port to the output port in dependence of a battery port inactivation signal generated by the control unit of the Bill. The port enabling circuits provide the option to disconnect one or more battery units from the output port. It can be used in case of malfunction, or if some batteries are not able to contribute to successful operation of the overall electrical system. Each battery interface port may for instance be associated with a respective charge current detection device that is arranged to detect an electric charge current in direction towards the battery interface port. The control unit can then be arranged to generate the battery port inactivation signal to disconnect battery units from the electrical system when a charge current is detected on any of the charge current detection devices. This way a robust fault handling is obtained. The port enabling circuits of the BIU can, if present, also be used to manage new batteries that are connected to the BIU. A high voltage battery which is abruptly connected to one of the battery interface ports may cause undesired surge current. Such surge currents can be avoided by inactivation of a battery interface port by the port enabling circuits.

[0026] According to some further aspects, the control unit is arranged to obtain temperature data related to a temperature of at least one battery unit connected to the BIU, and to generate the battery port inactivation signal in response to obtaining temperature data which fails to satisfy a temperature acceptance criterion. Thus, battery units running hot can be inactivated until they cool down sufficiently to be used again. This way a robust mechanism for avoiding battery unit overheating is obtained.

[0027] According to other aspects, the control unit is arranged to establish a data connection with one or more battery units connected to the battery interface ports, and to obtain information related to the one or more connected battery units. This information can then be used to optimize the operation of the Bill, and of the powertool, as will be explained in more detail below. The control unit can for instance be arranged to negotiate one or more operating parameters of the powertool, such as maximum current to be drawn from a given battery unit, via the data connection. The control unit can also be arranged to output configuration data to a motor control unit (MCU) of the powertool in dependence of the information related to the one or more connected battery units. According to some aspects the control unit may be configured to inactivate a battery unit which fails to communicate data that satisfies one or more predetermined battery specification requirements and / or a battery unit where operating parameters cannot be negotiated successfully by the control unit. This inactivation may be executed by means of the above-mentioned port enabling circuit. The data connection can also be used by the BIU control unit to detect when a battery is connected to a given battery interface port and when no battery is present. This allows the control unit of the BIU to actuate a breaker arrangement that galvanically isolates electrical terminals at an unused battery slot or compartment from the rest of the BIU circuit in order to reduce the risk that a person comes into contact with a live battery terminal in the unused battery slot or compartment. These aspects will be discussed in more detail below.

[0028] According to an example, at least one of the battery interface ports is associated with a breaker arrangement that is adapted to galvanically isolate the battery interface port from at least one other battery interface port of the BIU when the battery port is not in use, i.e., when no battery is connected at the battery port. This breaker arrangement can be used to disconnect a battery port which is not in use from the rest of the BIU, such that the unused battery port does not pose a risk to, e.g., an operator which may inadvertently come into contact with the electrical conductors of the battery compartment or battery slot of the unused battery interface port. The breaker arrangement allows a battery port where no battery unit is connected to be galvanically isolated from the battery ports in use in an automated manner and fail-safe manner.

[0029] The breaker arrangement may for instance comprise one or more mechanical breakers or switches which are arranged to be closed by a battery unit when inserted into a battery compartment, battery slot, or other battery support associated with the Bill. This way the battery port is galvanically isolated from the rest of the BIU and in particular from the other battery interface ports when no battery unit is supported in the battery compartment or slot, and then automatically connected as soon as a battery unit is connected to the battery port.

[0030] The breaker arrangement may also comprise a relay and a sensor, such as a Hall sensor. The sensor can be configured to detect when a battery unit is properly inserted into the battery compartment, battery slot, or battery support associated with the BIU. The control unit of the BIU can operate the relay in response to a signal from the sensor and thus automatically close the relay to connect the battery interface port to the rest of the BIU circuit when a battery unit is properly inserted into the battery compartment, battery slot, or battery support associated with the BIU.

[0031] According to another example, the control unit of the BIU is adapted to detect when a battery unit is inserted into the battery compartment, battery slot, or battery support associated with the BIU by receiving a communication signal from the battery unit, as discussed above. The control unit can then automatically close the breaker arrangement by sending a control signal to the breaker arrangement in order to connect the battery interface port to the rest of the BIU in response to receiving the communication signal from the battery unit connected to the battery interface port.

[0032] There are also disclosed herein methods, control units, and computer programs associated with the above listed technical effects and advantages. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realizes that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present disclosure will now be described in more detail with reference to the appended drawings, where

[0035] Figure 1 illustrates an example powertool in use;

[0036] Figure 2 shows a powertool electric system comprising an example BIU;

[0037] Figure 3 illustrates an example BIU with three battery interface ports;

[0038] Figure 4 shows an example transistor-based battery interface circuit;

[0039] Figures 5A-C are flow charts that illustrate methods;

[0040] Figure 6 shows an example control unit comprising processing circuitry;

[0041] Figure 7 shows an example BIU comprising breaker arrangements;

[0042] Figure 8A shows an example battery compartment; and

[0043] Figure 8B shows an example battery unit.

[0044] DETAILED DESCRIPTION The invention will now be described more fully hereinafter with reference to the accompanying drawings, in which certain aspects of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments and aspects set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0045] It is to be understood that the present invention is not limited to the embodiments described herein and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.

[0046] Figure 1 shows an operator using an example cordless powertool 100, in this case a battery powered leaf blower. The powertools discussed herein require significant power to operate and are normally used for extended periods of time. To keep the weight, size, and cost of battery units down, more than one battery unit 120 is used to provide the required electrical energy. The example leaf blower in Figure 1 shows two connected battery units 120, although it is appreciated that the techniques disclosed herein are not limited to any particular number of battery units. A battery interface unit (BIU) 110 is used to connect the two or more battery units to the power consumer or power consumers of the powertool, such as the motor of the leaf blower.

[0047] The BIUs and electrical systems discussed herein can also be applied in other types of handheld powertools such as concrete vibrators, chainsaws, and powercutters. Some of the BIUs and electrical systems discussed herein are also applicable in construction equipment such as battery powered compactors, floor saws, powertrowels and the like.

[0048] With reference also to Figure 2, the BIU 110 comprises two or more battery interface ports 210 for connecting respective battery units 120. The battery units 120 are normally of the same type and form factor, although some of the BIUs discussed herein may also be adapted to be connected to batteries of different type, i.e., batteries having different technical specifications in terms of energy storage capacity, maximum power output, operating temperature ranges, and so on.

[0049] The battery units 120 are normally replaceable and rechargeable battery units, which means that a battery unit can be removed from the battery interface port and placed in a separate charger to recharge the battery. The powertool 100 normally comprises battery bays, battery compartments, slots or other forms of battery supports configured to hold a battery unit in position during use of the powertool. The terms battery compartment and battery slot will be used interchangeably herein to denote a support for a replaceable battery unit. No special tools or the like are normally required to remove a replaceable battery unit from a battery interface port 210 of the Bill 110. An example battery compartment 800 and a matching battery unit 850 will be discussed below in connection to Figure 8B.

[0050] Many powertools can be operated using a smaller number of battery units than there are battery supports, i.e., not all battery supports of a powertool need to have attached batteries in order for the powertool to be operated. It may, for instance, be possible to operate a powertool with two battery compartments with only one battery, leaving the other battery compartment empty.

[0051] Operating a powertool with one or more empty battery compartments may pose a risk in that the electrical terminals of the empty battery compartments are exposed, which means that an operator may inadvertently come into contact with a live terminal. A solution to this problem will be discussed below in connection to Figure 7 and Figures 8A-B.

[0052] The BIU 110 comprises at least one output port 220 for connecting a power consumer 240 of the powertool 100 to the BIU 110. The output port 220 is normally a direct current (DC) port. Alternating current (AC) output ports are possible, in which case some type of inverter structure is required between the battery interface ports 210 and the output port 220.

[0053] The power consumer 240 is often but not always an electric motor. The electric motor 240 may be driven by a motor control unit (MCU) 230. The Bill 110 may be realized as a separate physical unit, e.g., enclosed by a BIU housing and physically separated from other components of the electrical system 200, such as the MCU 230 of the powertool 100.

[0054] Potting is the process of filling a complete electronic assembly with a solid or gelatinous compound. This is done to exclude water, moisture, or corrosive agents, and to increase resistance to shocks and vibrations. The Bl Us disclosed herein may at least in part be potted modules.

[0055] According to some other aspects the BIU 110 is integrated with the MCU 230 of the powertool 100.

[0056] Figure 2 also shows some optional peripheral modules 250 that may be used together with the BIU 110 to extend the capabilities of the electrical system 200 of the powertool 100. The peripheral units 250 may be connected to a system bus 260 of the electrical system 200, which is a data communications bus arranged to relay information between the different modules in the electrical system 200. Data communication busses of the kind shown in Figure 2 are generally known and will therefore not be discussed in more detail herein.

[0057] A fleet services module 251 provides an interface to an external fleet services system, such as a remote server 270. The fleet services module 251 , or a separate communications interface, may comprise a wired or wireless data communication link 275 between the electrical system 200 and the external fleet services system 270 in order to share status data and receive configuration data.

[0058] A user interface (Ul) module 252 provides Ul functionality to the electrical system 200, to the BIU 110, and / or to the powertool 100. The Ul module 252 may be complemented or replaced by an analog Ul module 253.

[0059] The electrical system 200 optionally comprises an interface 254 for an external switch signal, such as a front handle (FH) or hand guard switch signal or a chain brake (CB) switch signal that can be used to inactivate the tool in response to some event, or to prevent activation of the electrical system unless some criterion is satisfied. This type of function and interface is well known in the art and will therefore not be discussed in more detail herein. The electrical system 200 may also comprise one or more fans 255. The one or more fans 255 may be controlled at least in part based on the status of the battery units 120 as determined by the Bill, as will be discussed in more detail below.

[0060] Various service interfaces and development tool interfaces 280, 285 may be configured throughout the electrical system 200, as illustrated in Figure 2.

[0061] The different BIUs and powertool electrical systems discussed herein provide at least five main functions. It is appreciated that these five different main functions are not inextricably linked to each other but can be realized separately as stand-alone functions with respective advantages that do not depend on the presence of any of the other main functions.

[0062] The first of these main functions is to provide an approximation of an ideal diode function that is in its OFF-state when the output voltage of the BIU 110 is higher than the voltage at a given battery interface port 210, otherwise it is in its ON-state, possibly accounting for a fixed voltage margin or offset voltage value determined relative to a nominal operating voltage of the BIU. The OFF- state may be referred to as an open configuration and the ON-state may be referred to as a closed configuration. A technical effect of the ideal diode function is to allow electrical current to pass from a high voltage battery to the output port 220 of the BIU 110, while stopping electrical current from the output port 220 to a battery interface port associated with a low voltage battery.

[0063] With reference also to Figure 3, the second main function is to provide a battery input enable / disable switch, referred to herein as a port enabling circuit 330. The input enable / disable switch is preferably realized by a MOSFET transistor. The input enable / disable switch can be used to select which battery interface ports that are enabled. This switch function can be omitted for a system of reduced complexity and is therefore indicated by dashed boxes in Figure 3 below. The second main function is, however, comprised in a preferred realization of the BIU, since it can be used to connect batteries to the output port in a controlled manner. The battery input enable / disable switch may be particularly useful if batteries are connected or disconnected from the BIU during operation when the Bill is actively transmitting current to the power consumer of the powertool. Note however that the port enabling circuit 330 is separate from the transistor-based interface circuit 320 that realizes the ideal diode function.

[0064] The third function is to provide means for dissipation of excess electrical energy. An optional powersink circuit 350, schematically illustrated in Figure 3, is used to dissipate excess energy submitted from the load connected to the output port 220 of the BIU 110. The powersink function can also be omitted, e.g., in case an energy sink is implemented by the MCU 230 or elsewhere in the electrical system 200. A powersink of the type described herein is also not necessary in all types of powertools.

[0065] According to a fourth main function, a charge current detection / disable function 360 is implemented in order to monitor correct operation of the BIU 110 regarding that charging from one battery unit to another battery unit is not occurring. In case a charge current is detected, then the electrical system may take action such as powering off the system or disconnecting one or more battery units from the output port.

[0066] According to a fifth main function, a control function is included in the BIU 110 to, e.g., configure the BIU regarding enabled / disabled status of the inputs, permitted power draw by the load and estimation of the energy available in the connected battery units 120.

[0067] With reference to the example circuit schematically illustrated in Figure 3, the ideal diode function is approximated by a BIU 110 where each battery interface port 210 is connected to the output port 220 via at least one transistor-based interface circuit 320. Each such interface circuit 320 is associated with a closed configuration and an open configuration. Electric current is allowed to flow back and forth between the battery interface port 210 and the output port 220 in the closed configuration (as long as the port enabling circuit 330, if present, is not inactivated), while, in the open configuration electric current is allowed to flow from the battery interface port 210 to the output port 220 but not in reverse from the output port 220 to the battery interface port 210. Each interface circuit 320 is furthermore arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port 210 and the output port 220 satisfies an acceptance criterion. Electric current is thus allowed to pass from a battery unit 120 to the output port 220, but not in reverse from the output port 220 to the battery interface port 210.

[0068] According to an example, the acceptance criterion is satisfied if a difference in the voltage vB1 , vB2, vB3 of the respective battery interface port 210 compared to the voltage of the output port 220 lies within a predetermined range, such as when the voltage vB1 , vB2, vB3 of the respective battery interface port 210 is at least as high as the voltage of the output port 220, or exceeding a voltage of the output port 220 by some predetermined margin in order to account for an expected drop in voltage as the battery unit is subject to load. The margin may also be configured as a relative offset voltage determined in relation to, e.g., a voltage at the battery interface port. Thus, as soon as the voltage on a battery interface port becomes high enough in comparison to the voltage at the output port, the battery unit is connected by the Bill 110 and thus starts to contribute to powering the powertool 100. The output voltage of the BIU 110 will be the common output voltage of the battery units 120 connected to the output port 220 via the ideal diode functions 320.

[0069] It is noted that current will be allowed to flow from the battery interface port 210 to the output port 220 regardless of the state of the transistor-based interface circuit 320, at least as long as the port enabling circuit 330 is not inactivated. Thus, a battery unit with sufficient voltage will be able to feed current to the output port 220 even if the automatic transition by the interface circuit 320 fails for some reason.

[0070] Figure 4 illustrates an example realization 400 comprising the transistor-based interface circuit 320 and an example of its control circuitry 310. In this example the transistor-based interface circuit 320 comprises two transistors Q201 , Q204 connected in parallel between the battery interface port 210 and the output port 220. Two or more such transistors may be connected in parallel. By connecting transistors in parallel in this manner a higher electrical current can be conducted between the battery interface port and the output port, with reduced losses, which is an advantage. Note however that it is possible to use a single transistor also, given that a transistor of suitable operating characteristics is selected as the single transistor.

[0071] Electrical components marked Rxxx in Figure 4 may correspond to resistances.

[0072] Electrical components marked Cxxx in Figure 4 may correspond to capacitances.

[0073] CPH200, SSW200, GID200 are test points of the circuit. The point SSW200 is perhaps of particular interest, since it forms basis for one of the input voltages of the comparator function 410.

[0074] The transistor-based interface circuit 320 preferably comprises a metal-oxide- semiconductor field-effect transistor (MOSFET) with an intrinsic diode arranged to prevent electric current in direction from the output port 220 towards the battery interface port 210. MOSFET transistors will be discussed in more detail below.

[0075] The example BIU 110 shown in Figure 3 has three battery interface ports 210 and one output port 220 to the motor control unit. The BIU may generally comprise two or more battery interface ports 210, and one or more output ports 220.

[0076] The BIU 110 optionally includes a control function that is used to setup which batteries that are enabled and disabled and to retrieve information from the batteries regarding their type and capability. The control function of the BIU 110 may also provide configuration information to a connected load such as the MCU 230, e.g., regarding maximum allowable current or power to draw from the output port 220.

[0077] Each battery interface port 210 is connected to the output port 220 via a circuit that emulates an ideal diode function. The electrical power drawn from each battery interface port 210 is hence determined by the terminal voltage that the connected battery can produce given its design capability and status.

[0078] The capability of setting one or more battery inputs as enabled or disabled (by the port enabling circuits 330) allows the system to disconnect batteries with error status or that, e.g., have significantly lower current capability than the other batteries which could otherwise result in an unwanted product behavior.

[0079] The enabled / disabled status of the battery interface ports 210 may be configured at power-on or start-up of the electrical system 200.

[0080] A power cycling may in some cases be required after exchange or insertion of one or more batteries to enable it for use. Some systems may comprise an MCU with an input capacitance that is charged before the main electrical load is applied, often referred to as pre-charge. This procedure may need to be restarted in order to be able to use the new battery with higher voltage. An alternative to this kind of MCU “reboot” is to let the BIU and the MCU coordinate input capacitance management, which can be done for example when the system is at rest.

[0081] A common method for pre-charge of capacitors in an MCU, such as the MCU 230, is to operate a transistor device, arranged at the MCU input, in its linear region to control the flow of current into the capacitor. Using the same principle, it can be appreciated that the port enabling circuits 330 can also be used for pre-charge of the MCU input capacitance, which can facilitate input capacitance management overall.

[0082] The battery interface port enabling feature is not inextricably linked to any of the other features disclosed herein, and in particular not to any of the other four main functions of the electrical system 200 listed above. Consequently, there is disclosed herein a BIU 110 for a powertool 100. The BIU 110 comprises a control unit 310, 353, 360, two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer such as a motor 240 to the BIU 110. Each battery interface port 210 is connected to the output port 220 via at least one transistor-based interface circuit 320, Q201 , Q204. Each transistor-based interface circuit 320, Q201 , Q204 implements a diode function which prevents electric current from flowing from the output port 220 to the respective battery interface port 210. Each battery interface port 210 is connected to the output port 220 via a respective port enabling circuit 330 associated with an enabled configuration and a disabled configuration, where each port enabling circuit 330 is arranged to prevent or allow electric current in direction from the battery interface port 210 to the output port 220 in dependence of an inactivation signal 365 generated by the control unit 360. Each battery interface port 210 is furthermore associated with a respective charge current detection device 340 arranged to detect an electric charge current in direction towards the battery interface port 210, where the control unit 360 is arranged to generate the battery port inactivation signal 365 when a charge current is detected on any of the charge current detection devices 340.

[0083] An example electrical design of the circuit intended to emulate the ideal diode function is shown in Figure 4. Briefly described, it consists of a transistor-based circuit (in this example a MOSFET-based circuit) that is transitioned between an open and a closed configuration depending on the voltage that it sensed over the circuit. The intended function of the circuit in Figure 4 is to replicate the function of a diode but without the drawback of a forward voltage drop of 0.5-0.7V as is the case for most “normal” diodes.

[0084] In Figure 4 two parallel MOSFETs is used for lower on-state resistance and increased current rating. A comparator 410 is used to control the states of the MOSFETs. It is appreciated that other control options are available to replace or to complement the comparator-based design, such as operational amplifier (op-amp) based solutions or integrated circuit (IC) based solutions. In other words, the BIU 110 optionally comprises a comparator function 410 for each battery interface port 210. This comparator function 410 is arranged to determine the voltage difference indicative of a voltage difference between the battery interface port 210 and the output port 220 and to generate a control signal 415 indicative of the voltage difference, where the respective interface circuit 320 is arranged to automatically transition into its closed configuration in dependence of a state of the control signal 415. In other words, as soon as the voltage difference over the device becomes large enough to trigger a change in state of the output of the comparator 410, the respective interface circuit 320 automatically transitions into its closed configuration and vice versa. The comparator function forms part of the above-mentioned BIU control unit.

[0085] According to an example, the comparator function 410 compares the voltage over the transistors Q201 , Q204 at an offset, which means that the comparator device outputs a control signal 415 to automatically transition the transistors Q201 , Q204 into their closed configurations when the voltage on the battery side of the transistors (for instance at test point SSW200) is somewhat higher than the voltage at the output port side of the transistors. The offset may be configured at 0,1 % of a circuit voltage such as the voltage at the battery interface port 210, i.e., 25mV at 25V and 40mV at 40V.

[0086] Note that the comparator function 410 in Figure 4 uses the voltage level at point SSW200 for the comparison, i.e., an intermediate voltage value which is normally slightly lower than the battery voltage. Other reference voltages can also be used by the comparator, with the same or at least similar technical effect.

[0087] A MOSFET transistor is a commonly used component in modern electronics. The MOSFET is used in a wide variety of applications ranging from power conversion to signal amplification. MOSFETs are preferred for their high switching speed, low power consumption, and ability to handle large currents. MOSFETs come in two major types: N-channel and P-channel. The key regions of a MOSFET include the source, drain, gate, and body (or substrate). One important aspect of MOSFETs, particularly in power applications, is the presence of an intrinsic diode, also known as the body diode of the MOSFET.

[0088] In a typical MOSFET, the gate controls the conductivity between the source and drain. The MOSFET has an underlying semiconductor substrate that forms a junction with the source and drain. This structure, in essence, incorporates a p-n junction between the source and drain terminals, leading to the formation of the body diode. The p-n junction occurs because the source and drain are typically doped differently from the substrate (or body). For an N-channel MOSFET, the source and drain are N-type regions within a P-type body, creating a natural p-n junction. Similarly, for a P-channel MOSFET, the source and drain are P-type regions within an N-type body, also forming a p-n junction. The intrinsic diode in a MOSFET is a result of this p-n junction. When the MOSFET is turned off, referred to above as its open configuration, the body diode will conduct current if a reverse voltage is applied between the source and drain. Current will normally flow through the body diode if the drain-source voltage exceeds the forward voltage threshold, typically around 0.7V for silicon-based MOSFETs.

[0089] When a reverse voltage is applied across the MOSFET (i.e., drain more negative than source in an N-channel MOSFET), the intrinsic diode becomes forward biased and conducts current.

[0090] Like any p-n junction diode, the body diode exhibits a reverse recovery behavior. After conducting in the forward direction, if the voltage polarity changes, the diode does not stop conducting immediately. This recovery time may be an important parameter in high-frequency switching applications, as it can lead to energy losses and heat generation.

[0091] The forward voltage drop of the intrinsic diode can be higher than that of more specialized diodes such as Schottky diodes. In many circuits, designers prefer to use external diodes with lower forward voltage drops to reduce power losses.

[0092] While the body diode is an intrinsic part of the MOSFET, it also introduces limitations. For instance, in high-frequency circuits, the slow recovery of the body diode can lead to significant energy losses and electromagnetic interference (EMI). Compared to dedicated diodes, the body diode has a higher forward voltage, which can lead to reduced efficiency, especially in power-sensitive applications.

[0093] According to an implementation example comprising two MOSFETs arranged in parallel as the transistors Q201 and Q204 in Figure 4, between the battery interface ports 210 and the output port 220, the transistors have technical specifications according to the examples below. These example values and associated ranges have been found to yield a BIU implementation which is suitable for use with the type of powertools and construction equipment mentioned above, such as powertools operating at a nominal voltage of 36V, and a current up to around 50-80A.

[0094] Drain-source breakdown voltage (VDS) = 60V, or between 50V and 80V.

[0095] Gate-source threshold voltage (Vos-th) = 2-3.4V, or between 1 ,5V and 4.0V.

[0096] Drain-source on-state resistance (Ros-on) maximum at VGS of 10V = 0.0017Q, or between 0.0014Q and 0.00200.

[0097] Drain-source on-state resistance Ros-on maximum at VGS of 7.5V = 0.00200, or between 0.00170 and 0.00230.

[0098] Drain-source on-state resistance Ros-on maximum at VGS of 6V = 0.00260, or between 0.00220 and 0.00290.

[0099] Total gate charge (Qg) = 52nC, or between 46nC and 60nC.

[0100] Continuous drain current (Tj at 150 °C) = 100A, or between 80A and 120A, or at least 80A.

[0101] Pulsed drain current = 200A, or between 150A and 250A, or at least 150A.

[0102] Capacitances (VDS = 30 V, VGS = 0 V, f = 1 MHz).

[0103] Input capacitance (Ciss) = 5130pF, or between 5000pF and 5260pF.

[0104] Output capacitance (Coss) = 992pF, or between 950pF and 1030pF.

[0105] Reverse transfer capacitance (Crss) = 94pF, or between 90pF and 100pF.

[0106] Maximum power dissipation (Tc at 70°C) = 80W, or at least 70W.

[0107] According to a more general implementation example for difference system nominal voltages and currents, the transistor or transistors arranged between the battery interface ports 210 and the output port 220 may have a greatly varying specification in accordance with the voltage and current in the system as well as other factors like thermal management. For different systems with a nominal voltage of 18V and up to 150V or higher having a Drain-source breakdown voltage (VDS) specification between 30V and 200V would be suitable. The Drain-source on-state resistance (Ros-on) and other specifications will vary with for example the current rating of the system.

[0108] It is appreciated that MOSFET transistors are not the only types of transistors that can be used in this type of application. The present disclosure is not limited to MOSFET transistors.

[0109] The Bill 110 disclosed herein is intended to be used with two or more replaceable and rechargeable battery units that have similar properties and charge status. Under such conditions, the current draw will be relatively equal from all batteries, and they will effectively be used in parallel for the complete discharge cycle. Combinations of different battery types and / or capacities or batteries with varying statuses can as well be used, but:

[0110] If using one high capacity battery together with two lower capacity batteries, the current draw will normally be higher from the high capacity battery as the current distribution between batteries is largely determined by the open circuit voltage and impedance.

[0111] If using one fully charged battery together with two half-charged batteries, the current draw will dominantly be from the fully charged battery to begin with, and as its state-of-charge (and thereby open circuit voltage) approaches the other two batteries’ state-of-charge, the current draw will start to even out between the battery units.

[0112] The current from each battery may not be controlled by all Bl Us disclosed herein, and hence the full output current will in most cases be drawn from the battery unit with the highest voltage on load. The admissible output currents and / or power that is negotiated between the MCU and the BIU is hence easiest set to the lowest value for the connected battery units. It is appreciated that more advanced schemes can be contemplated. The short term output capability of the batteries can for instance be accounted for when setting the possible output current and power of the BIU, since the output current is normally shared relatively equal between batteries after some time. It is also possible to predict the current draw from the batteries to further improve the possible output current / power of the BIU in many situations. The losses per battery unit and the overall energy efficiency of the electrical system 200 will increase when current is drawn from more than one battery unit.

[0113] For two battery units the ohmic losses per battery will go from RiL2to 0,25RiL2when the load current iLis split between two battery units each with impedance R. The total losses for two batteries will be Q,5RiL2.

[0114] For three battery units the ohmic losses per battery will go from RiL2to approximately 0,lllRiL2when the load current iLis split between three battery units each with impedance R. The total losses for three batteries will be approximately 0,333RiL2.

[0115] In these examples the losses per battery is of interest for thermal management of the batteries, whereas the total losses is of interest for the energy efficiency.

[0116] Since the battery inputs of the BIU 110 are connected to the output of the BIU with an ideal diode function (or at least a circuit that closely emulates an ideal diode function), no charge current can flow from the output port 220 to the battery interface ports 210. Small amounts of energy can be generated from the motor control unit, e.g., during motor start-up and during motor running due to deceleration of the electric motor, which can raise the DC link voltage unless that excess energy is fed to the battery or otherwise dissipated. For this purpose, a powersink function is optionally included in the BIU 110. When the output voltage of the BIU exceeds the maximum voltage at the inputs, all the ideal diode functions at the inputs will be in their OFF-state and the powersink function can be activated to lower the voltage in the electrical system 200. The powersink function is normally operated in an ON / OFF manner using, e.g., a hardware or software implemented comparator taking the input and output voltages as inputs. An example realization of the powersink function 350 is schematically illustrated in Figure 3. According to this example realization, a control unit or function 353 monitors the voltage on the output port 220 and connects a resistive load 351 by operating the transistor 352 in case excess energy is detected. To summarize, the Bill 110 optionally comprises a powersink circuit 350 connected to the output port 220. The powersink circuit 350 comprises a resistive load 351 and a powersink control unit 353 arranged to connect the resistive load 351 to the output port 220 in order to dissipate excess electrical energy at the output port 220.

[0117] The powersink feature of the BIUs 110 discussed herein is not inextricably linked to any of the other features disclosed herein, and in particular not to any of the other four main functions of the electrical system 200 listed above. Consequently, there is disclosed herein a BIU 110 for a powertool 100. The BIU 110 comprises a control unit 310, 353, 360, two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer 240 to the BIU 110. Each battery interface port 210 is connected to the output port 220 via at least one transistorbased interface circuit 320, Q201 , Q204. Each transistor-based interface circuit 320, Q201 , Q204 implements a diode function which prevents electric current from flowing from the output port 220 to the respective battery interface port 210. The BIU 110 further comprising a powersink circuit 350 connected to the output port 220, where the powersink circuit 350 comprises a resistive load 351 and a powersink control unit 353 arranged to connect the resistive load 351 to the output port 220 in order to dissipate excess electrical energy at the output port 220.

[0118] With continued reference to Figure 3, a charge current detection and disable function 360 is optionally included in the BIU 110. This function disables all battery inputs 210 in the case of detecting a charge current that flows to at least one of the connected battery units. The normal function of the BIU 110 is that the output node can have a higher voltage than one or two of the battery inputs. This voltage must be blocked by the ideal diode function for each battery input to avoid cross-charging from one battery to another. In an example use case where, e.g., the battery connected to input 3 has the lowest voltage and the battery connected to input 1 has the highest voltage, and the input 3 has a component fault in the ideal diode function electronics so that the output node voltage cannot be blocked; all three inputs will be disabled by the charge current detection / disable function 360. In this manner, the hardware redundancy available is used to stop charge current into a battery by disabling the voltage source.

[0119] To summarize, each battery interface port 210 is optionally connected to the output port 220 via a respective port enabling circuit 330 associated with an enabled configuration and a disabled configuration, where each port enabling circuit 330 is arranged to prevent or allow electric current in direction from the battery interface port 210 to the output port 220 in dependence of a battery port inactivation signal 365 generated by the control unit 360. Note that the port enabling circuit 330 in the example is separate from the transistor-based interface circuits 320, both in control and in hardware design. The port enabling circuit 330 may also be integrated with the transistor-based interface circuits 320, such as if the two are comprised in the same integrated circuit (IC).

[0120] Each battery interface port 210 is optionally associated with a respective charge current detection device 340 arranged to detect an electric charge current in direction towards the battery interface port 210. In this case the control unit 360 can be arranged to generate the battery port inactivation signal 365 when a charge current is detected on any of the charge current detection devices 340.

[0121] The control unit 310, 353, 360 can furthermore be arranged to obtain temperature data related to a temperature of at least one battery unit 120, and to generate the battery port inactivation signal 365 in response to obtaining temperature data which fails to satisfy a temperature acceptance criterion.

[0122] According to some aspects, the control unit 310, 353, 360 is arranged to establish a data connection with one or more battery units 120 connected to the battery interface ports 210, and to obtain information related to the one or more connected battery units 120. The control unit 310, 353, 360 may, for instance, be arranged to negotiate one or more operating parameters of the powertool 100, such as maximum current to be drawn from a given battery unit 120, via the data connection. The control unit 310, 353, 360 is optionally also arranged to output configuration data to an MCU 230 of the powertool 100 in dependence of the information related to the one or more connected battery units 120.

[0123] The control unit 310, 353, 360 can also obtain data related to a technical specification of a battery unit connected to a battery interface port, such as a maximum current that can be provided by the battery unit. The control unit 310, 353, 360 can then generate the battery port inactivation signal 365 in response to detecting an operation outside of the technical specification of the battery unit, such as a breach of maximum output current.

[0124] Figures 5A-C show flow charts that illustrate methods. The methods correspond to use of one or more of the devices described herein.

[0125] Figure 5A illustrates a method, performed by a control unit 310, 353, 360 for connecting one or more battery units 120 to a power consumer 240 of a powertool 100 by a battery interface unit, BIU, 110. The method comprises configuring Sa1 two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer 240 of the powertool 100 to the BIU 110, where each battery interface port 210 is connected to the output port 220 via at least one transistorbased interface circuit 320, Q201 , Q204, associating Sa2 each interface circuit 320, Q201 , Q204 with a closed configuration and an open configuration, where the respective battery interface port 210 is connected to the output port 220 in the closed configuration and where electric current is allowed to flow from the battery interface port 210 to the output port 220 and not from the output port 220 to the battery interface port 210 in the open configuration, and transitioning Sa3 each interface circuit 320, Q201 , Q204 into its respective closed configuration when a voltage difference between the battery interface port 210 and the output port 220 satisfies an acceptance criterion.

[0126] Figure 5B illustrates a method, performed by a control unit 310, 353, 360 for connecting one or more battery units 120 to a power consumer 240 of a powertool 100 by a battery interface unit, BIU, 110, the method comprising configuring Sb1 two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer 240 of the powertool 100 to the Bill 110, where each battery interface port 210 is connected to the output port 220 via at least one transistorbased interface circuit 320, Q201 , Q204, configuring Sb2 each transistor-based interface circuit 320, Q201 , Q204 as a diode function which prevents electric current from flowing from the output port 220 to the respective battery interface port 210, configuring Sb3 a powersink circuit 350 at the output port 220, where the powersink circuit 350 comprises a resistive load 351 and a powersink control unit 353 arranged to selectively connect the resistive load 351 to the output port 220, and connecting Sb4 the resistive load 351 to the output port 220, by the powersink control unit 353 in case of excess electrical energy at the output port 220.

[0127] Figure 5C illustrates a method, performed by a control unit 310, 353, 360 for connecting one or more battery units 120 to a power consumer 240 of a powertool 100 by a battery interface unit, BIU, 110, the method comprising configuring Sc1 two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer 240 of the powertool 100 to the BIU 110, where each battery interface port 210 is connected to the output port 220 via at least one transistorbased interface circuit 320, Q201 , Q204, configuring Sc2 a respective port enabling circuit 330 associated with an enabled configuration and a disabled configuration between each battery interface port 210 and the output port 220, where each port enabling circuit 330 is arranged to prevent or allow electric current in direction from the battery interface port 210 to the output port 220 in dependence of a battery port inactivation signal 365 generated by the control unit 360, configuring Sc3 a respective charge current detection device 340 at each battery interface port 210, where each charge current detection device 340 is T1 arranged to detect an electric charge current in direction towards the battery interface port 210, and generating Sc4, by the control unit 360, the battery port inactivation signal 365 when a charge current is detected on any of the charge current detection devices 340.

[0128] Figure 6 schematically illustrates, in terms of a number of functional units, the general components of a control unit 310, 353, 360 for use with one or more functions of the Bills discussed herein. Processing circuitry 610 is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g., in the form of a storage medium 630. The processing circuitry 610 may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA.

[0129] Particularly, the processing circuitry 610 is configured to cause one or more control units 310, 353, 360, 600, to perform a set of operations, or steps, such as the methods discussed herein. For example, the storage medium 630 may store the set of operations, and the processing circuitry 610 may be configured to retrieve the set of operations from the storage medium 630 to cause the device to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuitry 610 is thereby arranged to execute methods as herein disclosed.

[0130] The storage medium 630 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0131] The device 310, 353, 360, 600 may further comprise an interface 620 for communications with at least one external device, such as a dust extractor or the like. As such the interface 620 may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline or wireless communication. The processing circuitry 610 controls the general operation of the control unit 310, 353, 360, 600, e.g., by sending data and control signals to the interface 620 and the storage medium 630, by receiving data and reports from the interface 620, and by retrieving data and instructions from the storage medium 630.

[0132] There is also disclosed herein a computer readable medium carrying a computer program comprising program code means for performing the methods discussed herein, when said program product is run on a computer. The computer readable medium and the code means may together form a computer program product.

[0133] Machines that are designed to accommodate two or more battery units connected in parallel can be operated for longer periods of time without interruption, while still maintaining compatibility with standard battery modules used across a product range which is an advantage. The operator has the flexibility to operate the machine with one or more batteries, depending on availability or required runtime. For example, an operator may continue working even if one battery is being recharged in a separate charger, or if one of the batteries has become defective.

[0134] However, such parallel connection of battery slots may in some cases introduce a safety concern. When only some of the battery interface ports of the BIU on a machine are occupied, the electrical connector terminals of the empty battery supports remain electrically live, since they are connected to the active battery units in parallel. This presents a potential electric shock hazard if a person accidentally touches the exposed connector pins, for instance by inserting a finger or a conductive object into the empty battery support.

[0135] The present disclosure addresses this potential safety issue by providing a system that galvanically isolates unused battery ports from the used battery ports of the BIU in an automated and fail-safe manner. The electrical terminals of a battery support remains galvanically isolated from the rest of the circuitry unless a corresponding battery is physically inserted and properly seated in the battery support. This safety function can be realized in various ways. In one embodiment, the battery slot is provided with one or more mechanical switches that are actuated by the physical presence of the battery. For example, when the battery is fully inserted into a battery compartment, a protruding portion or edge of the battery housing depresses a switch located near the rear end of the slot. The actuation of this switch closes a breaker and thereby connects the corresponding battery terminals to the rest of the Bill circuit. The breaker is automatically opened when the battery unit is removed from the battery support, thus galvanically isolating the battery terminals of the battery support.

[0136] For enhanced safety, it is advantageous to employ two or more such breakers positioned at different locations within the battery support. This configuration makes it practically impossible for a person to inadvertently close both breakers simultaneously while still being in contact with the live connector terminal. Only when both breakers are actuated by the correct geometry of the battery housing will the circuit be completed, thereby preventing accidental exposure to live voltage.

[0137] In another example embodiment, the presence of the battery unit in the battery support is detected magnetically. The battery unit may comprise a magnet or at least a magnetic material that is located at a defined position on its housing, corresponding to the location of a magnetic sensor such as a Hall sensor within the battery compartment. When the battery unit is inserted into the battery compartment, the magnetic field activates the sensor, which in turn controls an electrical relay or electronic switch to automatically connect the battery unit to the BIU. The electrical terminals of the battery compartment remain galvanically isolated from the rest of the BIU when no battery unit is detected by the magnetic sensor.

[0138] Alternatively, or in combination with the above, an electronic control unit such as a control unit of the BIU can be configured to detect the presence of a battery unit based on communication signals transmitted via a data pin of the battery unit. Many modern battery systems include such communication lines, e.g., for transmitting battery identification or voltage level information. The BIU control unit can detect these signals and only then enable an electronic switch (such as a MOSFET or relay) to connect the battery interface port to the rest of the Bill. The battery interface port remains galvanically isolated from the rest of the BIU when no such communication signals are received. The communication signaling may be configured as a periodic signaling, such that a removed battery unit can be detected without significant delay in a reliable manner.

[0139] To summarize, with reference to Figure 7 and to the example battery compartment and battery unit in Figures 8A-B, there is disclosed herein a BIU 110 where at least one of the battery interface ports 210 is associated with a breaker arrangement 710 that is adapted to galvanically isolate the battery interface port 210 and thus also the battery terminals of the corresponding battery compartment from at least one other battery interface port 210 of the BIU 110. A battery interface port 210 which has been galvanically isolated from other live electrical conductors will not pose a safety hazard to a person which accidentally comes into contact with the battery terminals of an empty battery support.

[0140] The breaker arrangement 710 may comprise a single breaker connected to the positive terminal of the battery port 210, or a breaker which disconnects both the positive and the negative terminal from the rest of the battery interface ports 210 of the BIU 110. In other words, the breaker arrangement 710 optionally comprises two or more mechanical breakers which are arranged to be closed by a battery unit 120, 850 when inserted into a battery compartment 800, battery slot, or battery support associated with the BIU 110. The breaker arrangements 710 of the BIU 110 are open in a default state such that the battery port is galvanically isolated from live electrical conductors of the BIU when no battery unit is received in the battery compartment 800, battery slot, or battery support.

[0141] Figure 8A shows an example battery compartment 800 which is configured to receive a matching battery unit 850. The battery compartment 800 comprises an electrical terminal 810 which is adapted to mate with the terminals 860 on the battery 850. Thus, as the battery 850 is inserted into the compartment 800 an electrical connection is formed between the replaceable battery and the battery interface port of the Bill. The example battery 850 is locked in place by spring-loaded latches 820. When the battery unit 850 is pushed all the way into the compartment 800, abutments 870 on the battery unit 850 engage spring-loaded supports 830 at the rear of the battery compartment 800, which mechanical engagement can be used to control mechanical switches that connect the electrical terminals 810 to the rest of the BIU electrical system. Other mechanical switches and breakers can of course also be used.

[0142] The breaker arrangement 710 may also comprise a relay which can be actuated by a control signal such as an electric control signal and a sensor 840 such as a Hall sensor that is configured to detect when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the BIU 110. The control unit 310, 353, 360 of the BIU 110 is arranged to control the relay in response to a signal from the sensor 840 to close the relay when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the BIU 110. The control unit automatically opens up the relay to galvanically isolate the battery terminals from the rest of the BIU circuit when no battery unit is detected by the sensor.

[0143] According to another example, the breaker arrangement 710 comprises a relay and the control unit 310, 353, 360 of the BIU 110 is adapted to detect when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the BIU 110 by receiving a communication signal from the battery unit 120, 850, and to control the relay in response to receiving the communication signal. The communication signaling is preferably periodic, which allows the control unit to also detect when a battery unit is removed from its batter support. This way the control unit can ensure galvanic isolation of the battery terminals of a battery support without a connected battery unit, and electrical connection of the terminals when a battery unit is inserted in the battery support. The features related to the breaker arrangement can be realized with advantage also without the Bill specific features discussed herein. Thus, there is disclosed a battery interface arrangement for a powertool 100 comprising at least one control unit, two or more battery interface ports 210 for connecting respective battery units 120, and at least one output port 220 for connecting a power consumer 240 of the powertool 100 to the battery interface arrangement, where at least a first battery interface port 210 out of the two or more battery interface ports 210 is associated with a breaker arrangement 710 adapted to galvanically isolate the first battery interface port 210 from at least one other battery interface port 210 of the BIU 110 when no battery unit 120, 850 is connected at the first battery interface port 210.

[0144] According to an example, the breaker arrangement 710 comprises one or more mechanical breakers 820, 830 which are arranged to be closed by a battery unit 120, 850 when inserted into a battery compartment 800, battery slot, or battery support associated with the first battery interface port 210.

[0145] According to an example, the breaker arrangement 710 comprises a relay 845 and a sensor 840, such as a Hall sensor, which is configured to detect when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the first battery interface port 210, where the control unit of the battery interface arrangement is arranged to control the relay 845 in response to a signal from the sensor 840 to close the relay 845 when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the first battery interface port 210.

[0146] According to an example, the breaker arrangement 710 comprises a relay 845 and the control unit of the battery interface arrangement is adapted to detect when a battery unit 120, 850 is inserted into the battery compartment 800, battery slot, or battery support associated with the first battery interface port 210 by receiving a communication signal from the battery unit 120, 850, and to control the relay 845 in response to receiving the communication signal.

Claims

CLAIMS1 . A battery interface unit, BID, (110) for a powertool (100), the BIU (110) comprising at least one control unit (310, 353, 360), two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), where each interface circuit (320, Q201 , Q204) is associated with a closed configuration and an open configuration, where electric current is allowed to flow back and forth between the battery interface port (210) and the output port (220) in the closed configuration, where electric current is allowed to flow from the battery interface port (210) to the output port (220) and not from the output port (220) to the battery interface port (210) in the open configuration, where each interface circuit (320, Q201 , Q204) is arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port (210) and the output port (220) satisfies an acceptance criterion, characterized in that the BIU (110) comprises a powersink circuit (350) connected to the output port (220), where the powersink circuit (350) comprises a resistive load (351 ) and a powersink control unit (353) arranged to connect the resistive load (351 ) to the output port (220) in order to dissipate excess electrical energy at the output port (220).

2. The BIU (110) according to claim 1 , where at least one of the transistorbased interface circuits (320, Q201 , Q204) comprises two or more transistors(Q201 , Q204) connected in parallel between the battery interface port (210) and the output port (220).

3. The Bill (110) according to claim 1 or 2, where at least one of the transistor-based interface circuits (320, Q201 , Q204) comprises a metal-oxide- semiconductor field-effect transistor, MOSFET (Q202, Q204) with an intrinsic diode arranged to prevent electric current in direction from the output port (220) towards the battery interface port (210).

4. The BIU (110) according to any previous claim, where the acceptance criterion is satisfied if a difference in voltage (vB1 , vB2, vB3) of the respective battery interface port (210) and a voltage of the output port (220) lies in a predetermined range.

5. The BIU (110) according to claim 4, where the acceptance criterion comprises a voltage (vB1 , vB2, vB3) of the respective battery interface port (210) exceeding a voltage of the output port (220).

6. The BIU (110) according to claim 4 or 5, where the acceptance criterion comprises a hysteresis margin, where each interface circuit (320, Q201 , Q204) is arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port (210) and the output port (220) exceeds a first threshold, where each interface circuit (320, Q201 , Q204) is arranged to automatically transition into its respective open configuration when the voltage difference between the battery interface port (210) and the output port (220) falls below a second threshold which is lower than the first threshold by the hysteresis margin.

7. The BIU (110) according to any previous claim, comprising a respective comparator function (410) for each battery interface port (210), the comparator function (410) being arranged to determine the voltage difference between the battery interface port (210) and the output port (220) and to generate a control signal (415) indicative of the voltage difference, where the interface circuit (320, Q201 , Q204) is arranged to automatically transition into its closed configuration in dependence of a state of the control signal (415).

8. The BIU (110) according to any previous claim, where each battery interface port (210) is connected to the output port (220) via a respective port enabling circuit (330) associated with an enabled configuration and a disabled configuration, where each port enabling circuit (330) is arranged to prevent or allow electric current in direction from the battery interface port (210) to the output port (220) in dependence of a battery port inactivation signal (365) generated by the control unit (360).

9. The BIU (110) according to claim 8, where each battery interface port (210) is associated with a respective charge current detection device (340) arranged to detect an electric charge current in direction towards the battery interface port (210), where the control unit (360) is arranged to generate the battery port inactivation signal (365) when a charge current is detected on any of the charge current detection devices (340).

10. The BIU (110) according to claim 8 or 9, where the control unit (310, 353, 360) is arranged to obtain temperature data related to a temperature of at least one battery unit (120), where the control unit (360) is arranged to generate the battery port inactivation signal (365) in response to obtaining temperature data which fails to satisfy a temperature acceptance criterion.

11. The BIU (110) according to any previous claim, where the control unit (310, 353, 360) is arranged to establish a data connection with one or more battery units (120) connected to the battery interface ports (210), and to obtain information related to the one or more connected battery units (120).

12. The BIU (110) according to claim 11 , where the control unit (310, 353, 360) is arranged to negotiate one or more operating parameters of the powertool (100), such as maximum current to be drawn from a given battery unit (120), via the data connection.

13. The BIU (110) according to claim 11 or 12, where the control unit (310, 353, 360) is arranged to output configuration data to a motor control unit, MCU, (230) of the powertool (100) in dependence of the information related to the one or more connected battery units (120).

14. The BIU (110) according to any previous claim, where the Bill (110) is enclosed by a BIU housing and physically separated from the MCU (230) of the powertool (100).

15. The BIU (110) according to any of claims 1-13, where the BIU (110) is integrated with a motor control unit, MCU, (230) of the powertool (100).

16. The BIU (110) according to any previous claim, where at least a first battery interface port (210) out of the two or more battery interface ports (210) is associated with a breaker arrangement (710) adapted to galvanically isolate the first battery interface port (210) from at least one other battery interface port (210) of the BIU (110) when no battery unit (120, 850) is connected at the first battery interface port (210).

17. The BIU (110) according to claim 16, where the breaker arrangement (710) comprises one or more mechanical breakers (820, 830) which are arranged to be closed by a battery unit (120, 850) when inserted into a battery compartment (800), battery slot, or battery support associated with the first battery interface port (210).

18. The BIU (110) according to claim 16 or 17, where the breaker arrangement (710) comprises a relay (845) and a sensor (840), such as a Hall sensor, which is configured to detect when a battery unit (120, 850) is inserted into the battery compartment (800), battery slot, or battery support associated with the first battery interface port (210), where the control unit (310, 353, 360) of the BIU (110) is arranged to control the relay (845) in response to a signal from the sensor (840) to close the relay (845) when a battery unit (120, 850) is inserted into the battery compartment (800), battery slot, or battery support associated with the first battery interface port (210).

19. The BIU (110) according to any of claims 16-18, where the breaker arrangement (710) comprises a relay (845) and where the control unit (310, 353, 360) of the BIU (110) is adapted to detect when a battery unit (120, 850) is inserted into the battery compartment (800), battery slot, or battery support associated with the first battery interface port (210) by receiving acommunication signal from the battery unit (120, 850), and to control the relay (845) in response to receiving the communication signal.

20. A powertool (100) comprising the Bill (110) according to any previous claim.21 . A method, performed by a control unit (310, 353, 360) for connecting one or more battery units (120) to a power consumer (240) of a powertool (100) by a battery interface unit, BIU, (110), the method comprising configuring (Sa1 ) two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), associating (Sa2) each interface circuit (320, Q201 , Q204) with a closed configuration and an open configuration, where the respective battery interface port (210) is connected to the output port (220) in the closed configuration and where electric current is allowed to flow from the battery interface port (210) to the output port (220) and not from the output port (220) to the battery interface port (210) in the open configuration, and transitioning (Sa3) each interface circuit (320, Q201 , Q204) into its respective closed configuration when a voltage difference between the battery interface port (210) and the output port (220) satisfies an acceptance criterion.

22. A battery interface unit, BIU, (110) for a powertool (100), the BIU (110) comprising a control unit (310, 353, 360), two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204),where each transistor-based interface circuit (320, Q201 , Q204) implements a diode function which prevents electric current from flowing from the output port (220) to the respective battery interface port (210), the BIU (110) further comprising a powersink circuit (350) connected to the output port (220), where the powersink circuit (350) comprises a load (351 ) and a powersink control unit (353) arranged to connect the load (351 ) to the output port (220) in order to dissipate excess electrical energy at the output port (220).

23. A method, performed by a control unit (310, 353, 360) for connecting one or more battery units (120) to a power consumer (240) of a powertool (100) by a battery interface unit, BIU, (110), the method comprising configuring (Sb1 ) two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), configuring (Sb2) each transistor-based interface circuit (320, Q201 , Q204) as a diode function which prevents electric current from flowing from the output port (220) to the respective battery interface port (210), configuring (Sb3) a powersink circuit (350) at the output port (220), where the powersink circuit (350) comprises a load (351 ) and a powersink control unit (353) arranged to selectively connect the load (351 ) to the output port (220), and connecting (Sb4) the load (351 ) to the output port (220), by the powersink control unit (353) in case of excess electrical energy at the output port (220).

24. A battery interface unit, BIU, (110) for a powertool (100), the BIU (110) comprising a control unit (310, 353, 360), two or more battery interface ports (210) for connecting respective battery units (120), andat least one output port (220) for connecting a power consumer (240) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), where each transistor-based interface circuit (320, Q201 , Q204) implements a diode function which prevents electric current from flowing from the output port (220) to the respective battery interface port (210), where each battery interface port (210) is connected to the output port (220) via a respective port enabling circuit (330) associated with an enabled configuration and a disabled configuration, where each port enabling circuit (330) is arranged to prevent or allow electric current in direction from the battery interface port (210) to the output port (220) in dependence of a battery port inactivation signal (365) generated by the control unit (360), where each battery interface port (210) is associated with a respective charge current detection device (340) arranged to detect an electric charge current in direction towards the battery interface port (210), where the control unit (360) is arranged to generate the battery port inactivation signal (365) when a charge current is detected on any of the charge current detection devices (340).

25. A method, performed by a control unit (310, 353, 360) for connecting one or more battery units (120) to a power consumer (240) of a powertool (100) by a battery interface unit, BIU, (110), the method comprising configuring (Sc1 ) two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), configuring (Sc2) a respective port enabling circuit (330) associated with an enabled configuration and a disabled configuration between each battery interface port (210) and the output port (220), where each port enabling circuit (330) is arranged to prevent or allow electric current in direction from thebattery interface port (210) to the output port (220) in dependence of a battery port inactivation signal (365) generated by the control unit (360), configuring (Sc3) a respective charge current detection device (340) at each battery interface port (210), where each charge current detection device (340) is arranged to detect an electric charge current in direction towards the battery interface port (210), and generating (Sc4), by the control unit (360), the battery port inactivation signal (365) when a charge current is detected on any of the charge current detection devices (340).

26. A battery interface unit, Bill, (110) for a powertool (100), the BIU (110) comprising at least one control unit (310, 353, 360), two or more battery interface ports (210) for connecting respective battery units (120), and at least one output port (220) for connecting a power consumer (240) of the powertool (100) to the BIU (110), where each battery interface port (210) is connected to the output port (220) via at least one transistor-based interface circuit (320, Q201 , Q204), where each interface circuit (320, Q201 , Q204) is associated with a closed configuration and an open configuration, where electric current is allowed to flow back and forth between the battery interface port (210) and the output port (220) in the closed configuration, where electric current is allowed to flow from the battery interface port (210) to the output port (220) and not from the output port (220) to the battery interface port (210) in the open configuration, where each interface circuit (320, Q201 , Q204) is arranged to automatically transition into its respective closed configuration when a voltage difference between the battery interface port (210) and the output port (220) satisfies an acceptance criterion.

Images