Battery system

Abstract

A battery system which includes a battery cabinet and battery packs inside the battery cabinet. A switch arrangement is connected to each battery pack. The switch arrangement is located either outside of the battery cabinet or within the battery cabinet in a separate enclosure. A first switch is provided between each battery pack and the switch arrangement, in order to selectively connect or disconnect the battery pack to / from the switch arrangement. An actuator operates the first switches simultaneously to connect or disconnect the battery packs to / from the switch arrangement. The switch arrangement has an operative mode and an inoperative mode. In the operative mode, it connects the plurality of battery packs in series in order to establish a system voltage which is higher than a battery voltage of the battery packs. In its inoperative mode, the switch arrangement ensures that there is no series connection between the battery packs.

Description

[0001] TITLE: BATTERY SYSTEM

[0002] BACKGROUND OF THE INVENTION

[0003] Traditional battery systems for industrial applications, particularly those used in trailers (e.g. transport refrigeration units (TRU)), face several challenges. Low voltage battery systems, while safe, require high current operation, leading to the need for expensive and heavy conductors. Additionally, power conversion to high-voltage DC or AC is inefficient and costly, and DC fast charging is not feasible due to the low terminal voltage of the battery. On the other hand, high voltage battery systems allow for efficient power conversion and DC fast charging but pose significant safety risks and require certified personnel for maintenance due to the dangerous high voltage levels.

[0004] US-6430692-B1 discloses a series-parallel battery array conversion system that switches batteries between series configuration for high-power loads and parallel configuration for low- power loads. However, this system lacks comprehensive safety features for maintenance operations and does not provide adequate isolation mechanisms to ensure safe working conditions when the system is powered down.

[0005] US-2018 / 099579-A1 describes a battery system with sub-batteries of different chemistries connected in parallel, where cell modules can be switched in and out of series circuits. While this system provides some flexibility in battery management, it does not address the fundamental safety concerns associated with high-voltage battery maintenance and lacks proper lockout / tagout mechanisms for service operations.

[0006] US-2019 / 013681 -A 1 discloses a device for reconfiguring rechargeable energy storage devices into separate battery connection strings using networks of switches. However, this system focuses primarily on reconfiguration flexibility and does not adequately address the safety requirements for maintenance personnel working on battery systems, particularly the need for proper electrical isolation and lockout procedures. US-20170 / 144565-A1 discloses a battery system with switching circuits for connecting battery modules in series or parallel configurations. However, this system primarily focuses on balancing and charging operations and does not provide adequate safety measures for maintenance personnel, lacking proper lockout / tagout mechanisms and comprehensive isolation monitoring systems required for safe service operations.

[0007] JP-2015216729-A describes a battery control device for electric vehicles that can disconnect battery units during impact situations. While this system provides some switching capability between battery units, it is specifically designed for crash scenarios and does not provide the comprehensive safety features needed for routine maintenance operations, including proper isolation monitoring and lockout / tagout procedures for service personnel.

[0008] The inventors wish to address at least some of the issues mentioned above.

[0009] SUMMARY OF THE INVENTION

[0010] In accordance with a first aspect of the invention there is provided a battery system which includes: a battery cabinet; a plurality of batteries / battery packs / battery cell modules (hereinafter only referred to as “batteries / battery packs”) which are located in the battery cabinet and which are electrically isolated from each other within the battery cabinet; a control arrangement which includes a switch arrangement which is electrically connected to each battery / battery pack of the plurality of batteries / battery packs, wherein the switch arrangement either outside of the battery cabinet or within the battery cabinet in a separate enclosure which is physically isolated from the battery cabinet; and a main control actuator, wherein a first switch is provided between each battery / battery pack and the switch arrangement in order to selectively connect or disconnect the battery / battery pack to / from the switch arrangement, wherein the main control actuator is configured to operate the first switches simultaneously in order to connect or disconnect the batteries / battery packs to / from the switch arrangement at the same time, wherein the switch arrangement has an operative mode and an inoperative mode, wherein when the switch arrangement is in its operative mode, it connects the plurality of batteries / battery packs in series in order to establish a system voltage which is higher than a battery voltage of any one of the plurality of batteries / battery packs, and when the switch arrangement is in its inoperative mode, the switch arrangement ensures that there is no series connection between the plurality of batteries / battery packs.

[0011] The system may include an electronics cabinet. The electronics cabinet may be located / positioned outside the battery the battery cabinet. The switch arrangement is located inside the electronics cabinet.

[0012] The first switches or part thereof may be located within the battery cabinet.

[0013] The control arrangement may include a master battery management system (BMS) which is operatively connected to the switch arrangement.

[0014] The battery system may include a locking mechanism which is configured to prevent the battery cabinet from being opened until: a. the main control actuator has switched the first switches to disconnect the plurality of battery packs from the switch arrangement; and / or b. the switch arrangement is in its inoperative mode.

[0015] The locking mechanism may be configured to only allow the battery cabinet to be opened after an electronic verification signal / message has been received.

[0016] The battery system may include a mechanism whereby if the battery cabinet is opened: a. the main control actuator automatically disconnects the plurality of battery packs from the switch arrangement; and / or b. the switch arrangement automatically switches to its inoperative mode.

[0017] The battery system may include an alert mechanism which is configured to alert users, when: the battery packs are connected to the switch arrangement; and / or the switch arrangement is in its operative mode. Each of the plurality of batteries / battery packs may be a low voltage battery / battery pack which has a voltage which is considered safe for a human. The voltage of each battery / battery pack may have a voltage which falls in DC voltage class A of ISO 6469-3. More specifically, each of the plurality of batteries / battery packs may be a low voltage battery / battery pack which has a DC (direct current) voltage of 60V or less. When the switch arrangement is in its operative mode, the series connection of the plurality of batteries / battery packs may result in a DC (direct current) system voltage of more than 60V (e.g. between 200V and 1000V). The switch arrangement may be operatively connectable to a power source in order to charge the series- connected plurality of batteries / battery packs from the power source, when the switch arrangement is in its operative mode. The plurality of batteries / battery packs may be charged directly at low voltage from a power source. The switch arrangement may be operatively connectable to a load in order to power the load from the series-connected plurality of batteries / battery packs, when the switch arrangement is in its operative mode. The power source may be a battery charger which forms part of the battery system, thereby allowing the series-connected plurality of batteries / battery packs to be charged via the battery charger. The battery charger may be a DC battery charger. Alternatively, the battery charger may be an AC (alternating current) battery charger. The battery charger may be an on-board charger or an off-board charger. The power source may be a power grid, photovoltaic panels, an energy axle (e-axle), a portable battery, a power generator (e.g. a diesel generator), etc.

[0018] The control arrangement may include a DC (direct current) to DC (direct current) converter which is operatively connected to the switch arrangement in order to convert the DC system voltage to a different DC voltage.

[0019] The control arrangement may include a converter which is operatively connected to the switch arrangement. The converter may be configured to convert DC power from the series- connected plurality of batteries / battery packs to AC power, in order to power an AC load, when the switch arrangement is in its operative mode. The converter may be a switch mode power supply (SMPS) converter.

[0020] Each battery / battery pack of the plurality of batteries / battery packs / battery cell modules may include a slave battery management system (BMS) which is operatively connected to the master BMS. The switch arrangement may include a second switch for each battery / battery pack via which the battery / battery pack can be connected in series with the other batteries / battery packs of the plurality of batteries / battery packs. The master BMS may be configured to monitor each battery / battery pack of the plurality of batteries / battery packs and to control the second switches of the switch arrangement, based on information obtained from the slave battery management systems of the plurality of batteries / battery packs. Each battery / battery pack of the plurality of batteries / battery packs may be electrically connected to the switch arrangement via an electrical cable / wire / busbar. The switch arrangement may include a second switch for each battery / battery pack of the plurality of batteries / battery packs in order to allow it to be switched in series with the other batteries / battery packs of the plurality of batteries / battery packs.

[0021] Each second switch may have (i) a first switch position in which it connects its corresponding battery pack in series with the other battery pack / battery packs of the plurality of battery packs and (ii) a second switch position in which it disconnects its corresponding battery pack from the series connection with the other battery pack / battery packs (i.e. a bridged position).

[0022] The master BMS may be configured to selectively operate the second switch for each battery pack of the plurality of battery packs for battery balancing purposes. The master BMS may be configured to selectively operate the second switch for each battery pack of the plurality of battery packs in order to disconnect a particular battery pack, which may have become defective, from the other battery packs.

[0023] The main control actuator may include a manually operable lever. The manually operable lever may form an integral part of the switch arrangement.

[0024] The switch arrangement may be housed in a contactor box / contactor housing. The contactor box / contactor housing may be located in the electronics cabinet.

[0025] Each first switch may be a lockout switch, more specifically a lockout / tagout (LOTO) switch.

[0026] The lock-out switch may be integrated into the battery / battery pack.

[0027] The control arrangement (together with the switch arrangement) may be configured to only change mode when no current is flowing. The control arrangement may monitor a charging or discharging current and only instruct the switch arrangement 18 to change position during a zero current condition (zero current switching).

[0028] The master BMS may be configured to perform an isolation monitoring function. The master BMS may include an isolation monitoring device which is configured to perform the isolation monitoring function. The isolation monitoring function implemented by the master BMS may include disconnecting or isolating a specific component of the battery system from a remaining part of the battery system, if the specific component does not meet a minimum isolation criteria.

[0029] Each slave BMS may be configured to perform an isolation monitoring function. Each slave BMS may include an isolation monitoring device which is configured to perform the isolation monitoring function. The isolation monitoring function implemented by each slave BMS may include disconnecting or isolating a specific battery of the plurality of batteries / battery packs from a remaining part of the battery system, if it does not meet a minimum isolation criteria. The disconnecting or isolating may be implemented using an internal switch, more specifically an internal lockout switch, of the specific battery.

[0030] The second switch for each battery pack of the plurality of battery packs may be configured to switch between: a. a series position in which it connects its corresponding battery pack in series with the other battery pack / battery packs of the plurality of battery packs; and b. a bridged position in which its corresponding battery pack is electrically bypassed or bridged out from the series connection with the other battery pack / battery packs of the plurality of battery packs.

[0031] The master BMS may be configured to control the operation of each second switch: for battery balancing purposes; and / or to bypass or bridge out a battery pack of the plurality of battery packs, if the particular battery pack has become defective.

[0032] In accordance with a second aspect of the invention there is provided a transport refrigeration unit (TRU) system which includes the battery system in accordance with the first aspect of the invention.

[0033] In accordance with a third aspect of the invention there is provided a vehicle / machine which includes the battery system in accordance with the first aspect of the invention.

[0034] In accordance with a fourth aspect of the invention there is provided an energy storage system which includes the battery system in accordance with the first aspect of the invention. In accordance with a fifth aspect of the invention, there is provided a battery system which includes: a plurality of batteries / battery packs; an electronics cabinet; a battery cabinet; and a control arrangement which includes: a switch arrangement which is electrically connected to each battery / battery pack of the plurality of batteries / battery packs, wherein the switch arrangement has an operative mode and an inoperative mode, wherein when the switch arrangement is in its operative mode, it connects the plurality of batteries / battery packs in series in order to establish a system voltage which is higher than a battery voltage of any one of the plurality of batteries / battery packs, and when the switch arrangement is in its inoperative mode, the switch arrangement ensures that there is no series connection between the plurality of batteries / battery packs, wherein the control arrangement is located in the electronics cabinet and the plurality of batteries / battery packs are located in the battery cabinet, whereby the electronics cabinet is separate from the battery cabinet.

[0035] Each battery / battery pack of the plurality of batteries / battery packs may be electrically connected to the switch arrangement via an electrical cable / wire. The switch arrangement may include a switch for each battery / battery pack of the plurality of batteries / battery packs in order to allow it to be switched in series with the other battery / battery pack or batteries / battery packs of the plurality of batteries / battery packs.

[0036] The switch arrangement may be housed in a contactor box. The contactor box may be positioned within the electronics cabinet.

[0037] A lock-out switch may be provided between each battery / battery pack and the switch arrangement, or the lock-out switch may be integrated into the battery / battery pack, or the main control actuator may be integrated into the battery / battery pack. In accordance with a sixth aspect of the invention there is provided a method of safe operation and servicing of a battery system, whereby the battery system includes a battery cabinet; a plurality of battery packs which are located in the battery cabinet and which are electrically isolated from each other within the battery cabinet; and a control arrangement which includes a switch arrangement which is electrically connected to each battery pack of the plurality of battery packs, wherein the switch arrangement is located either outside of the battery cabinet or within the battery cabinet in a separate enclosure which is physically isolated from the battery cabinet, and wherein a first switch is provided between each battery pack and the switch arrangement, in order to selectively connect or disconnect the battery pack to / from the switch arrangement, wherein the method includes: when the battery system needs to be operated, switching all the first switches simultaneously to connect the plurality of battery packs to the switch arrangement at the same time and connecting the plurality of battery packs in series in order to establish a system voltage which is higher than a battery voltage of any one of the plurality of battery packs; when servicing of the battery system is required, then performing the following steps prior to performing any servicing on the battery system:

[0038] (i) disconnecting the series connection between the plurality of battery packs; and

[0039] (ii) switching all the first switches simultaneously to disconnect the plurality of battery packs from the switch arrangement at the same time.

[0040] The step of switching all the first switches simultaneously to connect the plurality of battery packs to the switch arrangement at the same time, when the battery system needs to be operated, may be performed using an actuator which switches all the first switches simultaneously.

[0041] The step of switching all the first switches simultaneously to disconnect the plurality of battery packs from the switch arrangement at the same time, when servicing of the battery system is required, may be performed using the actuator.

[0042] The battery system may be the battery system in accordance with the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings:

[0044] Figure 1A shows a schematic diagram of a battery system in accordance with the invention during a charging cycle / process where a DC fast charger is used to charge a plurality of batteries of the battery system;

[0045] Figure 1 B shows a schematic diagram of a battery system in accordance with the invention during a discharging cycle / process where a uni-directional power converter is used to convert DC power from a switch arrangement of the battery system to AC power;

[0046] Figure 2A shows a schematic diagram of a battery system in accordance with the invention during a charging cycle / process where bidirectional power converter is used to convert AC power from an AC power source to DC power which is then used to charge the plurality of batteries of the battery system;

[0047] Figure 2B shows a schematic diagram of a battery system in accordance with the invention during a discharging cycle / process where bidirectional power converter is used to convert DC power from a DC power source to AC power which is then used to charge the plurality of batteries of the battery system;

[0048] Figure 3 shows a schematic diagram of a battery system in accordance with the invention;

[0049] Figure 4 shows a schematic diagram of a switch module / switch arrangement and a plurality of batteries which form part of the battery system shown in Figure 3;

[0050] Figure 5A shows a schematic diagram of an existing battery system, when in operation mode;

[0051] Figure 5B shows a schematic diagram of the existing battery system shown in Figure 5A where numerous lockout switches have been opened in order to prevent electricity flow (i.e. when in a lock-out mode - to help ensure safety);

[0052] Figure 6A shows a schematic diagram of a battery system in accordance with the invention; and

[0053] Figure 6B shows a schematic diagram of the battery system shown in Figure 6A, where numerous lockout switches have been opened in order to prevent electricity flow; Figure 7 shows a schematic illustration of the simultaneous operation of lockout switches via a lever;

[0054] Figure 8 shows a circuit diagram of a battery pack, which forms part of the battery system in accordance with the invention, with isolation monitoring; and

[0055] Figure 9 shows a schematic illustration of an example of various inputs and outputs of the battery system in accordance with the invention.

[0056] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0057] The present invention relates to a battery system 10 (see Figures 1-4). In one example, the battery system 10 may be incorporated in a transport refrigeration unit (TRU). It should however be noted that the battery system 10 is not limited only to refrigeration systems 12 and can be used in a variety of other applications, such as with vehicles or machines (e.g. forklifts or lift trucks). The battery system 10 may, for example, also be applied for materials handling, in maritime applications or in mining applications.

[0058] In one preferred embodiment illustrated in Figures 1-4, the battery system 10 includes a battery cabinet 310 and a plurality of battery packs / battery modules 14 (more specifically (N+1) battery modules) (hereinafter merely referred to as battery packs 14) which are located in the battery cabinet 310 and which are electrically isolated from each other within the battery cabinet. Each battery pack 14 is typically a low-voltage battery pack which has a battery voltage of less than 60V (e.g. 50V). More specifically, each battery pack 14 typically includes a plurality of battery cells which are connected in series and a battery management system (BMS). The BMS for each battery pack 14 is hereinafter referred to as a "slave" BMS (the master BMS 40 will be discussed further below).

[0059] The battery system 10 includes an electronics cabinet 205 and a control arrangement 16 which is located in a power electronics cabinet 205. The electronics cabinet 205 can be located either outside of the battery cabinet 310 or within the battery cabinet 310 in a separate enclosure which is physically isolated from the battery cabinet 310. The control arrangement 16 includes a switch arrangement / switch module 18 (hereinafter only referred to as the "switch arrangement 18") which is electrically connected to each battery pack 14. More specifically, the switch arrangement 18 includes a switch 20.1-20.5 (collectively hereinafter referred to as 20) for each battery pack 14, whereby the switches 20 (e.g. electro-mechanical or semiconductor switches) are configured to connect / switch the battery packs 14 in series during an operative mode of the switch arrangement 18. A switch, more specifically a lockout switch 206 (see Figures 6A and 6B), is provided between each battery pack 14 and the switch arrangement 18 in order to selectively connect or disconnect the battery pack 14 to / from the switch arrangement 18. More specifically, the lockout switch 206 may be an internal switch within the battery pack and which is configured to selectively connect or disconnect the internal battery terminals from an external connector which extends to the switch arrangement 18. A main control actuator 232 is configured to operate the lockout switches 206 simultaneously in order to connect or disconnect the battery packs 14 to / from the switch arrangement 18 at the same time. When connected in series, the voltage of the battery system 10 typically ranges between 200V and 1000V (or higher). This enables DC (direct current) fast-charging and allows for a highly efficient energy transfer to power high-voltage DC and / or AC loads. The DC fast charging may be done by an off-board DC fast charger. The battery system 10 may also include an on-board charger (e.g. an AC-DC charger). The on-board charger may be installed in the power electronics cabinet 205 (discussed further below). However, when the switch arrangement 18 is in an inoperative / lockout mode, the series connection between the battery packs 14 are terminated by the switches 20, which results in a low-voltage environment where the highest voltage in the system 10 is the battery voltage of 50V (which is less than 60V), thereby creating a safe environment for technicians to work on the various parts of the battery system 10 (e.g. during service and maintenance).

[0060] The battery system 10 includes a master battery management system (BMS) 40. The system 10 also includes one or more switch mode power supply (SMPS) converters 22 (these converters may however be located outside the system 10 as well). The SMPS converters 22 serve as an interface between the system voltage and external loads and sources.

[0061] In one example (see Figures 1A and 1 B), the converter 22 is a uni-directional power converter module. In this example, the converter 22 is active during a discharge phase / mode. For example, during charging, an off-board DC fast-charger 24 can be used to DC fast-charge the battery packs 14 via the switch arrangement 18 (see Figure 1A). It should however be noted that charging may also be done using an on-board charger (discussed further below). During a discharge phase / mode, DC and / or AC loads can be powered via the switch arrangement 18 and converter module 22 (with high efficiency) (see Figure 1 B).

[0062] In another example (see Figures 2A and 2B), the converter 22 is a bi-directional power converter module. During charging, a grid connection (400VAC - 3 phase) can be connected via the converter 22 and switch arrangement 18 to the battery packs 14 (see Figure 2A). The battery packs 14 can also be charged by DC fast charging via the switch arrangement 18. During discharging, DC and / or AC loads can be powered via the switch arrangement 18 and the converter module 22 (with high efficiency) (see Figure 2B)

[0063] The number of low-voltage battery packs 14 used in the hybrid battery system can be adjusted, as shown in Figure 3. This flexibility allows the total battery capacity (kWh) to vary accordingly. For TRU's, the total battery capacity could be up to 100-200 kWh, but for materials handling / maritime / mining equipment the total battery capacity could be larger, (e.g. MWh's).

[0064] One limitation is that the system voltage should remain between 200V and 1000V (possibly higher, e.g. 1250V for megawatt charging) to facilitate DC fast charging. For other loads or power sources, energy will be transferred using the SMPS converter 22 which converts the system voltage to the required DC or AC voltage levels. When the voltage difference between both sides of the SMPS converter 22 is minimized, the efficiency of energy transfer increases.

[0065] The switch arrangement 18 allows the entire system 10 to be turned on or off. Additionally, if one battery pack 14 fails (see the battery indicated by reference sign 21 in Figure 4), the terminals can be bridged (see reference sign 23), ensuring that the system 10 remains operational as long as the remaining voltage is between 200V and 1000V.

[0066] In one embodiment / example, to prevent arching of switches, the switch arrangement will only change mode when no current is flowing. More specifically, the master BMS 40 may monitor the charging or discharging current and the switch arrangement 18 may change position only during a zero current condition (zero current switching).

[0067] As mentioned the individual battery packs 14 feature an integrated slave BMS that communicates with the system-level master BMS 40. This setup enhances redundancy and meets higher safety standards. If battery packs 14 of different capacities are used, or if battery wear has led to discrepancies, the system 10 will still operate seamlessly. The master BMS 40 is configured to selectively enable and disable battery packs 14 to ensure the overall battery system remains balanced and prevents overcharging / undercharging of the individual battery packs 14.

[0068] The slave BMS units provide information (e.g. state of health (SOH), state of charge (SOC)) to the master BMS 40. The master BMS 40 can control the complete system 10 accordingly and switch battery modules 14 ON or OFF if required.

[0069] The system 10 illustrated in Figure 2A-4 includes the following operational / functional modes:

[0070] On mode: during charging battery packs and / or powering a load.

[0071] Stand by mode: where the unit is on - the battery packs 14 are connected in series - but no charging or powering of a load occurs.

[0072] Off mode - where the battery packs 14 are disconnected from each other - only low- voltage battery units / battery packs 14 remain. This off mode can include a lockout mode which may be physically lockable (by means of the main control actuator 232), to prevent switching on the system accidentally.

[0073] As mentioned, the batteries / battery packs 14 are housed in the battery cabinet 310 (see Figure 6), while the power electronics (e.g. switch arrangement 18, DC / DC converter 306 (described later) and AC / DC inverter 211 (described later)) are housed in the power electronics cabinet 205. LOTO switches 206 located in each battery / battery pack 14 are operated simultaneously via a single lever 19 (more specifically a LOTO lever). More specifically, the lever 19 is provided on an exterior of the battery cabinet 310. Moving and locking this lever in an OFF position de-energizes the system 10, ensuring safety during service and maintenance operations. This lever 19 is operated using the main control actuator 232. Similarly, LOTO switches 204.1 , 204.2 (described in more detail below) located in the power electronics cabinet 205 are operated simultaneously via a lever or device 230. In a slight alternative example, the levers 19, 230 could be replaced with a rotational switch or another type of switching means.

[0074] In a preferred implementation, the battery cabinet 310 can accommodate a number of batteries / battery packs 14 up to the maximum available positions. The main control actuator 232 serves two functions simultaneously: it activates the LOTO switch contacts and mechanically locks all batteries / battery packs 14. This design ensures that batteries / battery packs can only be moved in or out when the LOTO lever is in the OFF position. Figure 7 provides a schematic representation of the dual function of the LOTO switch.

[0075] When batteries / battery packs 14 are removed from the system 10, the mechanical design ensures that the internal Lockout / Tagout (LOTO) switch cannot be operated through manual intervention or any other means.

[0076] There are several possible implementations to achieve the same objectives. While a mechanical LOTO implementation is currently the industry standard, a partial or fully electronic solution is also feasible using devices such as contactors, solenoids, and other components.

[0077] As mentioned, to work on high-voltage battery systems, service technicians must have the appropriate training and certification. As a result, low-voltage battery systems are preferred. When the proposed battery system 10 is turned off, only fully isolated low-voltage battery packs 14 remain. This allows for maintenance and repair work (and switching of battery packs 14) to be conducted without the need for additional certification, precautions, or associated costs.

[0078] Safety Features

[0079] The battery system 10 incorporates several key safety features designed to ensure safe operation and maintenance:

[0080] Switch Box for High Voltage Control: The switch arrangement 18 (which may be housed in a contactor box 306 inside the power electronics cabinet 205) enables high voltage only during the operation mode. When the switch arrangement 18 is in its operative mode, it connects the plurality of battery packs 14 in series to establish a system voltage higher than the individual battery pack voltages. When in its inoperative mode, the switch arrangement 18 ensures that there is no series connection between the battery packs 14, maintaining only safe low-voltage levels throughout the system. Lockout Safety System: Each battery pack 14 has an internal lockout switch 206 to disconnect the battery pack 14 from the external connector and switch arrangement 18. A specified number of low-voltage battery packs 14 can fit in the modular battery cabinet 310, within a predefined maximum capacity. The battery packs 14 are secured in their designated positions, ensuring both mechanical fixation and electrical connection. The lockout lever 19 of the main control actuator 232 allows for manual operation. This lever 19 can be secured in a safe position to prevent accidental re-energization using lockout devices and tags. All applied battery packs 14 should be secured, and the battery cabinet 310 should be closed before the lockout switch lever can be changed from a safe mode to an enable mode. Only the lever 19 can operate the lockout switches 206. When the lever 19 changes position, all the lockout switches 206 also change position simultaneously through the main control actuator 232.

[0081] Lockout / Tagout (LOTO) Procedure: The lockout switches 206 described above are designed to facilitate proper lockout / tagout procedures. A typical LOTO procedure involves the following steps: (1) preparation - identifying all energy sources and understanding the system shutdown procedure; (2) notification - informing all affected personnel that maintenance will be performed; (3) shutdown - turning off the equipment using normal operating controls; (4) isolation - operating the lockout switches 206 (by using the main control actuator 232) to isolate the equipment from its energy sources; (5) lockout - applying lockout devices (such as locks) to the lockout lever 19 to prevent them from being operated; (6) tagout - attaching warning tags to identify the person responsible for the lockout and warn against operation; (7) verification - testing that the equipment cannot be restarted and that it is properly isolated. The main control actuator 232 enables simultaneous operation of all lockout switches, ensuring complete system isolation during maintenance procedures.

[0082] Electrical Isolation: The battery packs 14 are separated and isolated as low-voltage units within the battery cabinet 310. Reinforced isolation is provided between the battery packs (and other live parts) and the protective earth (PE). The isolation state / condition is monitored by an isolation monitoring device.

[0083] Isolation enhances safety by ensuring that if a human body makes a connection between the protective earth (PE) and a live part, safety can still be ensured, as it results in only a small leakage current. To monitor the isolation state, an earth leakage current measurement and protection device is used. If the leakage current exceeds a set threshold, the entire system will automatically shut down to ensure safety.

[0084] Isolation monitoring may be implemented for safety purposes. Each low-voltage battery 14 may be equipped with an isolation monitoring device which may form an integral part of the slave BMS. A central part of the system 10, which includes the switch arrangement 18, power electronics and the master BMS 40, also features an insulation monitoring device as an integral part of the master BMS 40.

[0085] From a safety approach perspective, the high-voltage battery system 10 is an isolated “floating system”, meaning that there is no direct electrical connection between any of the high-voltage parts and the chassis ground. Isolation is a critical factor in ensuring the safety of a high- voltage battery system. Several factors can lead to the degradation or loss of isolation in these systems. Faults in components within the BMS 40 or the battery cells can create pathways for leakage current. Additionally, environmental factors such as high humidity, temperature fluctuations, and contaminants can affect insulation and result in leakage. Over time, the materials used in batteries can also degrade, increasing the risk of leakage.

[0086] While any single point of failure in isolation may not significantly impact the system's overall operation, it poses a potential life risk when service engineers come into contact with high- voltage live parts. Therefore, it is crucial to implement a mechanism for detecting any loss of isolation in the entire system 10. This mechanism should disable the operation and activate a warning signal. The isolation resistance should be at least 500 Q / V between the high-voltage live components and the chassis ground.

[0087] Detection method

[0088] Insulation monitoring devices (IM Ds) are typically connected between high-voltage conductors and the chassis ground within a system. These devices can be activated using either a constant or pulsating measuring voltage, depending on their design. The IMD measures the resulting current, which allows the insulation resistance to be calculated based on Ohm’s Law. If the insulation resistance falls below a specific threshold, an alarm signal is triggered.

[0089] Insulation Monitoring Implementation

[0090] Various techniques are available in the insulation monitoring market, and one popular method is the electric bridge switch. This method is recommended in safety standards such as I EC 61851-23. The electric bridge switch method involves switching a known resistive branch across the isolation barrier. Under normal operation, no current flows through the resistor bridge because there is no conductive path to the protective earth (PE). This indicates that the system is safe and there are no isolation failures.

[0091] In Figure 8, a battery pack 14 with isolation measurement is depicted using bridge switches. A negative side switch (Sn) and a positive side switch (Sp) are used to temporarily break the isolation barrier with a known resistive divider path (Rp - Rsense or Rn - Rsense) that connects between DC+ and PE, and DC- and PE, respectively. During the measurement process, the two resistor branches are activated at different times. The current flowing through the isolation barrier impedance (Zp and Zn) is proportional to the bus voltage, the isolation impedance, and the activated resistive branch. By measuring the voltage drop across the sense resistor, one can determine the actual isolation resistance.

[0092] The master BMS and the slave BMS devices may be equipped with isolation monitoring. This distributed detection approach allows for individual monitoring of the isolation levels of all components in a decoupled state. If the isolation of any component fails, the failure can be localized, and if possible, that specific component can be isolated from operation. In the event that a battery pack does not meet the minimum isolation criteria, internal lockout switches 206 can be locked in an OFF position to prevent any connection with the remaining system 10. This setup enhances redundancy while still allowing the battery system 10 to operate, with one battery pack excluded.

[0093] Reference is now specifically made to Figures 5A-6B.

[0094] Figures 5A and 5B show an example of an existing battery system 200. The system 200 has a single large battery 201 (50V - may have a capacity of up to 210kWh) that powers a compressor 202 of a refrigerator through electronics (more specifically power electronics 203) which are located in an electronics cabinet 205 (more specifically a power electronics cabinet 205). The system 200 has two main functional modes, namely an operation mode and a lockout mode. Figure 5A demonstrates the operation mode and the existing voltages in different sections of the system 200. As illustrated in Figure 5A, the system 200 includes a lockout device 230 which includes two lockout switches 204.1 , 204.2. The system 200 also includes a lockout device 232 which has a lockout switch 206. When in operation mode, the switches 204.1 , 204.2, 206 are closed and connect different sections to each other. The lockout switch 204.1 is located between the power electronics 203 and the compressor 202, while the lockout switch 204.2 is located between the power electronics 203 and a power grid 205 (for charging). The switch 206 is located between the battery pack 201 and the power electronics 203. In the operating mode, the low-voltage battery is connected to the power electronics 203. The voltage is then increased to drive a motor of the refrigerator compressor 202. More specifically, a DC-DC converter 208 raises the voltage to 600 DC. The 600 DC is then converted to 400 AC by a DC-AC (direct current to alternating current) inverter 211 in order to power the compressor 202. The voltage of the power electronics and compressor motor sides is therefore more than 60V, but the voltage of the battery is less than 60V. It should be noted the operating mode may include an on mode, a standby mode and an off mode, since it is possible to run the system out of the standby / off modes, as the lockout switches 204.1 , 204.2, 206 are closed.

[0095] Figure 5B shows the lock-out mode and the existing voltages in different sections of the system 200. All the lockout switches 204.1 , 204.2, 206 are open in this mode. In this mode, the different sections of the system 200 are completely isolated by the lockout switches 204.1 , 204.2, 206. Moreover, discharge circuits are provided to discharge any remaining voltage in the system 200. Thus, the only potential that remains in the system is the battery voltage, which is <60V in this mode.

[0096] The system is designed with safety as a priority, ensuring that no high-voltage nodes are present during the off mode by utilizing lockout switches. These measures reduce the required certification level for technicians, promoting safer and more accessible maintenance.

[0097] Figures 6A and 6B show an example of a battery system / hybrid battery system 300 in accordance with the invention and to a transport refrigeration unit (TRU) 302 which incorporates the battery system 300. In Figures 6A and 6B, a low voltage battery pack up to 105kWh is shown. However, it will be appreciated that the battery capacity is not limited to 105kWh and it could be significantly more, e.g. 210kWh.

[0098] The main difference between the existing system 200 shown in Figures 5A and 5B and the battery system / hybrid battery system 300 shown in Figure 6A and 6B, is the arrangement of the battery packs 308 and the addition of a contactor box 306 in the power electronics cabinet 205. The rest of the system 300 is similar to the system 200. A primary aim of the battery system 300 is to have low-voltage battery packs 308, and to locate any high-voltage connections to the power electronics cabinet 205, so that the battery pack 308 is presented and considered as a low- voltage (<60V) and safe component. However, instead of a large power battery pack (found in the existing system 200), up to 16 low power battery packs 308 (e.g. 50V- ) or more are placed in a battery cabinet 310. Then, the outputs of all battery packs 308 are connected to the contactor box 306 in the power electronics cabinet. In this contactor box 306, the battery packs' outputs are placed in series, by means of switches, to increase the voltage. Thus, there is no high-voltage (>60V) connection in the battery cabinet 310.lt should be noted that each battery pack 308 may be mounted within the battery cabinet 310 such that they are individually removable from the cabinet (e.g. in order to replace a faulty battery pack). In a slight alternative arrangement, (N+1) independent battery cabinets may be provided (e.g. with a terminal voltage of 60V), connected via wires / connectors to the switch arrangement 18 / master BMS 40.

[0099] Figure 6A illustrates the battery system 300 during an operating mode and indicates existing voltages in different sections of the system 300. The battery system 300 also includes two main control actuators 230, 232 (also referred to as lockout devices 230, 232). These main control actuators 230, 232 can be coupled and operated simultaneously. The main control actuator 232 is mechanically / operatively connected to each of the lockout switches 206 (which are each connected to an associated battery pack 308) so that the main control actuator 232 can open and close the lockout switches 206 simultaneously (e.g. by operating its lever). The main control actuator 230, on the other hand, is mechanically / operatively connected to two lockout switches 204.1 , 204.2 so that the main control actuator 230 can open and close the lockout switches 204.1 , 204.2 simultaneously (e.g. by operating its lever). In the operation mode, the lockout switches 204.1 , 204.2, 206 are all closed, and power is flowing through all sections. In this mode, the output of each battery pack is 50V, and high-voltage connections exist only in the power electronics cabinet 205 and load refrigerator and grid power supply sections 202, 205. In this operating mode, the outputs of the battery packs 308 are connected to the contactor box 306, where they are placed in series (using switches). Then, a contactor box output voltage is regulated through power electronics to drive a load, e.g. a motor of a refrigerator compressor 202. In this mode, the voltage of each battery pack 308 remains 50V.

[0100] During a lock-out mode, all lockout switches 204.1 , 204.2, 206 are open and there is no power flowing in the system. Figure 6B demonstrates this mode and the existing voltages in different sections of the system 300. In this mode, the different sections of the system 300 are completely isolated by the lockout switches 204.1 , 204.2, 206. Moreover, a DC-bus is discharged in order to avoid any electric shock hazards. In the battery system 300, a monitoring system may be integrated which monitors all voltages in the system 300. Moreover, this monitoring system measures the voltage of the DC-bus and controls a passive circuit to waste the remaining energy in the DC-bus.

[0101] Thus, the only voltage remaining in the system 300 are the battery voltages, which are lower than 60V. During this mode, the trailer technicians are allowed to work on the trailer section and the low-voltage battery packs. In one embodiment of the system 300, one or more monitoring circuits are implemented to check continuously if the voltage of the contactor box input is below 60V. If it detects that there is any voltage higher than 60V in the battery cabinet 310, a warning status signal / alarm is shown / initiated. Trailer technicians are then not allowed to work on the trailer. During the operation, due to operation of the high voltage components, such as the compressor and AC grid voltage, , the system voltage is more than 60VDC, hence the entire system is classified as high voltage. During the lock-out mode, the battery packs 308 are isolated from the rest of the system 300 by lockout switches 204.1 , 204.2, 206 and the system voltage is below 60V. If multiple battery packs 308 are used in series, the lockout switches 204.1 , 204.2, 206 create multiple low-voltage battery packs, disconnected from each other, to allow a trailer mechanic to safely work on the trailer on which the battery system 10, 300 is installed. The lockout device may comprise a means to prevent unintentional re-connection (e.g. by other persons), e.g. a lock, key, et cetera.

[0102] Figure 9 shows a schematic illustration of an example of various inputs and outputs of the battery system 10. The battery system 10 may be connected to different power sources, such as the power grid, photovoltaic panels, an energy axle (e-axle), a portable battery, a power generator (e.g. a diesel generator), etc.

[0103] The battery system 10 may include a locking mechanism which is configured to prevent the battery cabinet from being opened until: a. the main control actuator 232 has switched the lockout switches 206 to disconnect the plurality of battery packs 308 from the switch arrangement 18; and / or b. the switch arrangement 18 is in its inoperative mode.

[0104] The locking mechanism may be further configured to only allow the battery cabinet to be opened after an electronic verification signal / message has been received.

[0105] The battery system 10 may include a mechanism whereby if the battery cabinet 310 is opened: a. the main control actuator 232 automatically disconnects the plurality of battery packs 308 from the switch arrangement 18; and / or b. the switch arrangement 18 automatically switches to its inoperative mode.

[0106] The battery system 10 may include an alert mechanism which is configured to alert users (e.g. via a visual warning (e.g. a light or via a user interface) and / or an audible warning), when: the battery packs 308 are connected to the switch arrangement 18; and / or the switch arrangement 18 is in its operative mode.

[0107] When the battery system 10 needs to be operated, all the lockout switches 206 are operated simultaneously to connect the plurality of battery packs 14 to the switch arrangement 18 at the same time. The plurality of battery packs 14 are then connected in series. When servicing of the battery system 10 is required, then the following steps are implemented prior to performing any servicing on the battery system 10: (i) The series connection between the plurality of battery packs 14 are disconnected; and

[0108] (ii) Thereafter, the lockout switches 206 are switched simultaneously to disconnect the plurality of battery packs 14 from the switch arrangement 18 at the same time.

[0109] From the above, it should be clear that the battery system 10 in accordance with the invention combines the advantages of both low and high voltage systems (as described in the background of the invention) while mitigating their respective disadvantages. This is achieved by connecting multiple low-voltage battery packs in series using a switch arrangement 18, which helps to provide safe electrical and mechanical connections even in harsh environments. The switch arrangement includes isolation switches to help ensure safety during service and maintenance, particularly when exchanging battery packs. The system is designed to be fail-safe, with lockout devices to prevent accidental operation.

Claims

CLAIMS1 . A battery system which includes: a battery cabinet; a plurality of battery packs which are located in the battery cabinet and which are electrically isolated from each other within the battery cabinet; a control arrangement which includes a switch arrangement which is electrically connected to each battery pack of the plurality of battery packs, wherein the switch arrangement is located either outside of the battery cabinet or within the battery cabinet in a separate enclosure which is physically isolated from the battery cabinet; and a main control actuator, wherein a first switch is provided between each battery pack and the switch arrangement, in order to selectively connect or disconnect the battery pack to / from the switch arrangement, wherein the main control actuator is configured to operate the first switches simultaneously in order to connect or disconnect the battery packs to / from the switch arrangement at the same time, wherein the switch arrangement has an operative mode and an inoperative mode, wherein when the switch arrangement is in its operative mode, it connects the plurality of battery packs in series in order to establish a system voltage which is higher than a battery voltage of any one of the plurality of battery packs, when the switch arrangement is in its inoperative mode, the switch arrangement ensures that there is no series connection between the plurality of battery packs.

2. The system of claim 1 , which includes an electronics cabinet, and wherein the switch arrangement is located inside the electronics cabinet.

3. The system of claim 1 , wherein the first switches are located within the battery cabinet.

4. The battery system of claim 1 , wherein the control arrangement includes a master battery management system (BMS) which is operatively connected to the switch arrangement.

5. The battery system of claim 1 , which includes a locking mechanism which is configured to prevent the battery cabinet from being opened until: a. the main control actuator has switched the first switches to disconnect the plurality of battery packs from the switch arrangement; and / or b. the switch arrangement is in its inoperative mode.

6. The battery system of claim 1 , which includes a mechanism whereby if the battery cabinet is opened: a. the main control actuator automatically disconnects the plurality of battery packs from the switch arrangement; and / or b. the switch arrangement automatically switches to its inoperative mode.

7. The battery system of claim 5, wherein the locking mechanism is configured to only allow the battery cabinet to be opened after an electronic verification signal / message has been received.

8. The battery system of claim 5 which includes an alert mechanism which is configured to alert users, when: the battery packs are connected to the switch arrangement; and / or the switch arrangement is in its operative mode.

9. The battery system of claim 1 , wherein a. each of the plurality of battery packs is a low voltage battery pack which has a DC (direct current) voltage of 60V or less, b. when the switch arrangement is in its operative mode, the series connection of the plurality of battery packs results in a DC (direct current) system voltage of more than 60V, c. the switch arrangement is operatively connectable to a power source in order to charge the series-connected plurality of battery packs from the power source, when the switch arrangement is in its operative mode, and d. the switch arrangement is operatively connectable to a load in order to power the load from the series-connected plurality of battery packs, when the switch arrangement is in its operative mode.

10. The battery system of claim 9 wherein the power source is a battery charger which forms part of the battery system, thereby allowing the series-connected plurality of battery packs to be charged via the battery charger.

11. The battery system of claim 9, wherein the power source is a power grid, photovoltaic panels, an energy axle (e-axle), a portable battery or a power generator.

12. The battery system of claim 4, wherein the control arrangement includes a converter which is operatively connected to the switch arrangement, wherein the converter is configured to convert DC power from the series-connected plurality of battery packs to AC power, in order to power an AC load, when the switch arrangement is in its operative mode.

13. The battery system of claim 12, wherein the converter is a switch mode power supply (SMPS) converter.

14. The battery system of claim 4, wherein each battery pack of the plurality of battery packs includes a slave battery management system (BMS) which is operatively connected to the master BMS, wherein the switch arrangement includes a second switch for each battery pack via which the battery pack can be connected in series with the other battery pack / battery packs of the plurality of battery packs, and wherein the master BMS is configured to monitor each battery pack of the plurality of battery packs and to control the second switches of the switch arrangement, based on information obtained from the slave battery management systems of the plurality of battery packs.

15. The battery system of claim 4, wherein each battery pack of the plurality of battery packs is electrically connected to the switch arrangement via an electrical cable / wire, and whereby the switch arrangement includes a second switch for each battery pack of the plurality of battery packs in order to allow it to be switched in series with the other battery pack / battery packs of the plurality of battery packs.

16. The battery system of claim 14, wherein a. each of the plurality of battery packs is a low voltage battery pack which has a DC (direct current) voltage of 60V or less,b. when the switch arrangement is in its operative mode, the series connection of the plurality of battery packs results in a DC (direct current) system voltage of more than 60V, wherein the control arrangement includes a DC (direct current) to DC (direct current) converter which is operatively connected to the switch arrangement in order to convert the DC system voltage to a different DC voltage.

17. The battery system of claim 14, wherein each second switch has (i) a first switch position in which it connects its corresponding battery pack in series with the other battery pack / battery packs of the plurality of battery packs and (ii) a second switch position in which it disconnects its corresponding battery pack from the other battery pack / battery packs.

18. The battery system of claim 14, wherein the master BMS is configured to selectively operate the second switch for each battery pack of the plurality of battery packs for battery balancing purposes.

19. The battery system of claim 14, wherein the master BMS is configured to selectively operate the second switch for each battery pack of the plurality of battery packs in order to disconnect a particular battery pack, which has become defective, from the other battery packs.

20. The battery system of claim 1 , wherein the main control actuator includes a manually operable lever.

21. The battery system of claim 1 , wherein the switch arrangement is housed in a contactor box.

22. The battery system of claim 1 , wherein each first switch is a lock-out switch.

23. The battery system of claim 14, wherein the master BMS is configured to perform an isolation monitoring function.

24. The battery system of claim 14, wherein each slave BMS is configured to perform an isolation monitoring function.

25. The battery system of claim 24, wherein the isolation monitoring function includes disconnecting or isolating a specific battery of the plurality of batteries from a remaining part of the battery system, if it does not meet a minimum isolation criteria.

26. The battery system of claim 23, wherein the isolation monitoring function implemented by the master BMS includes disconnecting or isolating a specific component of the battery system from a remaining part of the battery system, if the specific component does not meet a minimum isolation criteria.

27. The battery system of claim 14, wherein the second switch for each battery pack of the plurality of battery packs is configured to switch between: c. a series position in which it connects its corresponding battery pack in series with the other battery pack / battery packs of the plurality of battery packs; and d. a bridged position in which its corresponding battery pack is electrically bypassed or bridged out from the series connection with the other battery pack / battery packs of the plurality of battery packs.

28. The battery system of claim 27, wherein the master BMS is configured to control the operation of each second switch: for battery balancing purposes; and / or to bypass or bridge out a battery pack of the plurality of battery packs, if the particular battery pack has become defective.

29. A transport refrigeration unit (TRU) system which includes the battery system of claim 1.

30. A vehicle which includes the battery system of claim 1.

31. A method of safe operation and servicing of a battery system, whereby the battery system includes a battery cabinet; a plurality of battery packs which are located in the battery cabinet and which are electrically isolated from each other within the battery cabinet; and a control arrangement which includes a switch arrangement which is electrically connected to each battery pack of the plurality of battery packs,wherein the switch arrangement is located either outside of the battery cabinet or within the battery cabinet in a separate enclosure which is physically isolated from the battery cabinet, and wherein a first switch is provided between each battery pack and the switch arrangement, in order to selectively connect or disconnect the battery pack to / from the switch arrangement, wherein the method includes: when the battery system needs to be operated, switching all the first switches simultaneously to connect the plurality of battery packs to the switch arrangement at the same time and connecting the plurality of battery packs in series in order to establish a system voltage which is higher than a battery voltage of any one of the plurality of battery packs; when servicing of the battery system is required, then performing the following steps prior to performing any servicing on the battery system:(iii) disconnecting the series connection between the plurality of battery packs; and(iv) switching all the first switches simultaneously to disconnect the plurality of battery packs from the switch arrangement at the same time.

32. The method of claim 31 , wherein the step of switching all the first switches simultaneously to connect the plurality of battery packs to the switch arrangement at the same time, when the battery system needs to be operated, is performed using an actuator which switches all the first switches simultaneously; and the step of switching all the first switches simultaneously to disconnect the plurality of battery packs from the switch arrangement at the same time, when servicing of the battery system is required, is performed using the actuator.

33. The method of claim 31 , wherein the battery system is the battery system as claimed in claim 1.

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