Battery-electrically powered mobile work machine, designed as a forklift truck, with a traction battery

Abstract

Battery-electrically powered mobile work machine designed as a forklift truck, with a traction battery designed as a high-performance battery (2) and having a battery trough (4) within which modules (3) are arranged, each consisting of at least one battery cell, characterized in that a braking resistor (6) is integrated into the traction battery, wherein the braking resistor (6) is arranged within the battery trough (4) and is thermally connected to the battery trough (4), wherein the braking resistor (6) is mounted on a side wall (5) of the battery trough (4).

Description

[0001] The invention relates to a traction battery for a battery-electrically powered mobile work machine. In particular, the invention relates to a traction battery for a battery-electrically powered mobile work machine, such as a forklift truck, which is designed as a high-performance battery and has a battery tray within which modules are arranged, each consisting of at least one battery cell.

[0002] Traction batteries are used to operate battery-electric mobile machinery, particularly industrial trucks such as forklifts. These batteries are typically interchangeable and can be inserted into a battery compartment. Once discharged, they can be replaced with a fully charged traction battery. Currently, these traction batteries are generally lead-acid batteries, in which a chemical reaction between sulfuric acid and lead stores electrical energy. With these conventional lead-acid batteries, it is possible to draw energy from or recharge the traction battery across the entire temperature range that can occur during the operation of an industrial truck, for example, during regenerative braking.

[0003] Newer technologies now allow for the production and industrial use of batteries and accumulators that offer improved performance. These batteries can be described as high-performance batteries, characterized by a higher energy density relative to weight and / or volume compared to lead-acid batteries, and by the use of a different energy storage technology. Many high-performance batteries also feature the ability to deliver high power during discharge and / or charge at high power. The typical energy densities relative to weight and / or volume of a high-performance battery are higher than, and outside the range of, the corresponding parameters for lead-acid batteries, at least for one of these two values.

[0004] While nickel-cadmium batteries do not offer a significant weight advantage, they do have a higher energy density per unit volume. Other well-known technologies for accumulators or rechargeable batteries using nickel include nickel-metal hydride, nickel-iron, nickel-hydrogen, nickel-zinc, and silver-zinc. Sodium-nickel chloride and sodium-sulfur accumulators are also known.

[0005] However, lithium-ion batteries are increasingly being used on a larger scale. These batteries have achieved a level of reliability suitable for mass production, are characterized by high energy density, exhibit only a minimal memory effect, and allow for high-power discharge and charging. Various lithium-ion battery technologies are also known, such as lithium polymer, lithium cobalt dioxide, lithium air, lithium titanate, lithium iron phosphate, lithium manganese, and tin-sulfur lithium ions.

[0006] The use of such high-performance batteries is particularly advantageous in vehicles and, for example, industrial trucks, because due to the high energy density in relation to the volume, a larger amount of electrical energy can be stored in the given installation space for the battery, thus increasing the range of a vehicle or the operating time of the industrial truck.

[0007] High-performance batteries of this type require additional safety and operational control measures. Therefore, monitoring and control devices are incorporated, collectively known as a battery management system. This system monitors the condition of individual battery cells or modules, as well as the overall condition of the high-performance battery.

[0008] A disadvantage of such high-performance batteries, and especially lithium-ion batteries, is that they exhibit different operating behavior compared to lead-acid batteries, particularly at these temperatures. The potential regenerative current into the traction battery is limited at low temperatures due to chemical processes. To achieve the full charging and recuperation capacity of the traction battery at low ambient temperatures, it is therefore known to implement temperature control for the traction battery, in particular a heating system, which maintains the traction battery at a defined temperature. However, this is relatively complex and expensive, and may require additional connections to the traction battery, such as to a liquid heat exchanger circuit.Especially with smaller traction batteries in industrial trucks, the unfavorable surface area to volume ratio can lead to a very rapid drop in battery temperature when parked outdoors in low temperatures.

[0009] For the driving characteristics of a forklift truck, it is also desirable that a consistently high recuperation current can always be delivered by the drive system during braking, ensuring the driver always experiences the same braking behavior. Therefore, if the traction battery cannot absorb a recuperation current, additional effort must be made to integrate a braking or power resistor with an additional power control into the forklift truck, as is known from the prior art for dissipating braking energy, in order to enable electric braking even at low ambient temperatures.

[0010] It is also known to provide electric heating for the high-performance battery, but this is expensive, requires additional space and leads to undesirable energy consumption.

[0011] Since a high-performance battery, when fully charged, can absorb even a small amount of additional current, even briefly, compared to a conventional lead-acid battery, there is also the problem that, immediately after commissioning a forklift truck with a fully charged high-performance battery, even if the traction battery is at the correct operating temperature, it cannot absorb any recuperation current.

[0012] The present invention is therefore based on the objective of providing a traction battery that avoids the aforementioned disadvantages and in which a recuperation current can be absorbed in as many operating states and at as many operating temperatures as possible.

[0013] This problem is solved by a traction battery having the features of independent claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0014] The problem is solved according to the invention by integrating a braking resistor into a traction battery for a battery-electrically driven mobile work machine, in particular a forklift truck, which is designed as a high-performance battery and has a battery trough within which modules are arranged, each consisting of at least one battery cell.

[0015] By integrating a power resistor, also referred to here as a braking resistor, into the traction battery, it is possible that whenever the traction battery cannot accept an externally supplied charging current, particularly a recuperation current during braking of a forklift truck, this current is diverted to the braking resistor. In this way, part or all of the recuperation current that the traction battery cannot absorb by charging its modules or battery cells can be directed to the braking resistor. This can occur, for example, if the individual modules are not fully capable of absorbing the current due to a low operating temperature of the high-performance battery.It is also conceivable that immediately after commissioning a fully charged traction battery, if recuperation occurs, a charging current cannot be drawn because high-performance batteries must not be overcharged. In such a case, the current can also be briefly directed to the braking resistor. This is generally possible even if the traction battery is at normal operating temperature, as it has a large overall mass and the time constant for heating and dissipating heat is such that the energy can be absorbed briefly as heat.When a high-performance battery is used as a traction battery instead of a lead-acid battery, the advantage is that no changes in operating behavior are noticeable to the driver or operator. This is because, by integrating a braking resistor into the traction battery, recuperation current can be absorbed in all operating conditions, similar to a lead-acid battery. No special modifications to the forklift are required for operation with a high-performance battery; in particular, there is no need to integrate a power resistor as a braking resistor, which would regularly require additional cooling, such as water cooling. The recuperation current can be routed to the braking resistor via the traction battery's normal power connections.The battery tray can be any type of open-topped enclosure, although a lid can also create a completely enclosed enclosure.

[0016] Advantageously, a battery management system, which includes monitoring and control devices for the modules, directs a recuperation current into the braking resistor.

[0017] Such a battery management system, for example, prevents overcharging of a high-performance battery and allows only a maximum permissible charge under unfavorable operating conditions. If the battery management system automatically diverts excess recuperation current to the braking resistor and thereby controls it, the operation of the industrial truck or mobile work machine is simplified. Recuperation current generated by electric braking can always be directed to the traction battery, and the battery management system automatically distributes it between potential charging of the traction battery and diversion to the braking resistor.

[0018] In a favorable further development of the traction battery, the battery management system directs the recuperation current into the braking resistor depending on the temperature, especially if the operating temperature of the traction battery is too low.

[0019] If the traction battery's capacity to absorb energy is limited due to low temperatures, this can quickly warm the traction battery and restore its full performance.

[0020] Advantageously, if the traction battery's operating temperature is too low, the battery management system directs current from the traction battery to the brake resistor in order to heat it up.

[0021] This has the advantage of eliminating the need for a separate heating device for the traction battery, and allows full performance, especially the maximum possible discharge current, to be achieved quickly by rapidly bringing the traction battery up to operating temperature.

[0022] In a favorable embodiment, the braking resistor is arranged inside the battery tray and is thermally connected to the battery tray.

[0023] It is advantageous to mount the braking resistor on a side wall of the battery tray.

[0024] The battery tray usually consists of a steel housing and therefore has a high heat absorption capacity. Furthermore, the metal allows the heat to be distributed and dissipated over a large area.

[0025] The braking resistor can be located in place of a module.

[0026] It is advantageous to have two or more braking resistors distributed within the traction battery inside the battery tray.

[0027] This allows the heat to be distributed more broadly within the traction battery, particularly across multiple modules. Dividing the heat across several braking resistors also simplifies integration into the traction battery. Furthermore, it is possible to divide the modules into power classes, allowing for further optimization of the heat input to the traction battery depending on the operating conditions. This also makes control simpler and less prone to failure. Theoretically, it is also conceivable to position braking resistors outside or on the outer surface of the battery tray. However, an internal arrangement is advantageous and preferable, as it provides mechanical protection.

[0028] The high-performance battery can be a lithium-ion battery.

[0029] The braking resistor(s) can be driven as power resistors using IGBTs, but control via MOSFETs in bridge configuration as power switching elements is also conceivable. Furthermore, it is possible to create a resonant circuit by additionally integrating an inductor, particularly an induction coil, which would prevent feedback effects from the current flow into the braking resistor.

[0030] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiment shown in the schematic figure. The figure shows a traction battery. 1 , which are used as high-performance batteries 2 is trained and modules 3 in a battery tray 4 features. On one side wall 5 is on the inside of the battery tray 4 a braking resistor 6 arranged, which is provided by a battery management system 7 is being targeted.

[0031] When recuperation current is fed into the traction battery via power connections not shown during electric braking of a mobile work machine 1 is redirected and this is not passed through the modules 3 can be recorded, for example, the operating temperature of the traction battery 1 If the battery management system is too low, it will initiate a change in the battery management system. 7 the excess portion of the current or the entire recuperation current into the braking resistor 6 um, which is over the battery tray 4 thereby the traction battery 1 Overall, it was heated.

Claims

[1] Traction battery for a battery-electrically powered mobile working machine, in particular a forklift truck, which is a high-performance battery ( 2 ) is trained and has a battery tray ( 4 ) has within which modules ( 3 ) are arranged, each consisting of at least one battery cell, characterized by that a braking resistor is included in the traction battery ( 6 ) is integrated. [2] Traction battery according to claim 1, characterized by that a battery management system ( 7 ), the monitoring and control devices for the modules ( 3 ) includes a recuperation current into the braking resistor ( 6 ) leads. [3] Traction battery according to claim 2, characterized by that the battery management system ( 7 ) the recuperation current into the braking resistor ( 6) conducts in a temperature-dependent manner, especially when the traction battery's operating temperature is too low ( 1 ). [4] Traction battery according to claim 2 or 3, characterized by that the battery management system ( 7 ) at too low an operating temperature of the traction battery into the braking resistor ( 6 ) Power from the traction battery ( 1 ) directs it to heat them up. [5] Traction battery according to any one of claims 1 to 4, characterized by that the braking resistance ( 6 ) within the battery tray ( 4 ) and thermally with the battery tray ( 4 ) is arranged in a connected manner. [6] Traction battery according to claim 5, characterized by that the braking resistance ( 6 ) on a side wall ( 5 ) of the battery tray ( 4 ) is mounted. [7] Traction battery according to any one of claims 1 to 6, characterized by that the braking resistance ( 6) instead of the position of a module ( 3 ) is arranged. [8] Traction battery according to any one of claims 1 to 7, characterized by that two or more braking resistors ( 6 ) are present, distributed throughout the traction battery ( 1 ) within the battery tray ( 4 are arranged. [9] Traction battery according to any one of claims 1 to 8, characterized by that the high-performance battery ( 2 ) is a lithium-ion battery.

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