Method for equalizing the charge states of a large number of electrochemical energy storage cells of an electrochemical energy storage system

Abstract

Method for equalizing the charge states of a large number of electrochemical energy storage cells of an electrochemical energy storage system.

Description

[0001] The invention is based on a method for equalizing charge states of a plurality of electrochemical energy storage cells of an electrochemical energy storage device, a device for equalizing charge states of a plurality of electrochemical energy storage cells of an electrochemical energy storage device, and a use of the method and / or the device according to the preamble of the independent claims. State of the art

[0002] Typically, different charge levels of battery cells in lithium-ion batteries are balanced using passive balancing circuits. For this purpose, cells with a higher charge level are discharged via ohmic resistors, converting electrical energy into heat.

[0003] This electrical energy is no longer available to the battery and therefore to the electric drive.

[0004] Document US 2021 / 399553 A1 discloses a battery management system of a battery cell assembly having a plurality of cells, comprising a plurality of first cell balancing resistors and a plurality of first cell balancing switches connected between a positive electrode and a negative electrode of a corresponding first cell of the plurality of cells; and a plurality of second balancing resistors and a plurality of second balancing switches connected between the positive electrode and the negative electrode of the corresponding first cell.

[0005] Document US 9,172,258 B2 discloses a cell balancing circuit that controls a balanced discharge of a plurality of battery cells, the cell balancing circuit comprising a balancing part that detects the voltages of the battery cells, a controller that responds to an output of the balancing part to select one of the battery cells for discharging the cell, and a resistance controller that controls the discharge of the selected cell.

[0006] The object of the present invention is to further improve the state of the art. This object is achieved by the features of the independent claims. Disclosure of the inventionAdvantages of the invention

[0007] The procedure according to the invention with the characterizing features of the independent claims has the advantage that the method for adjusting charge states of a plurality of electrochemical energy storage cells of an electrochemical energy storage device comprises the following steps: a) determining charge states of the plurality of electrochemical energy storage cells; b) comparing the determined charge levels with specified target charge levels; c) controlling at least one switch for electrically connecting at least one compensating resistor in parallel to at least one of the electrochemical energy storage cells depending on the comparison; d) discharging electrochemical energy storage cells which have a significantly higher state of charge by means of the at least one compensating resistor for converting electrical energy into heat; e) controlling a heat transport device for heat transport of the generated heat by means of a heat transport medium in order to reuse the heat generated by the compensating resistor for maintenance purposes, in particular heating a desiccant within the electrochemical energy storage device, heating seals of the electrochemical energy storage device against corrosive creep and / or temperature-activated change opening of the electrochemical energy storage device.

[0008] This advantageously reduces heat losses and reuses balancing energy. Furthermore, the energy efficiency of the electrochemical energy storage system is improved.

[0009] Further advantageous embodiments are the subject of the subclaims.

[0010] A device according to the invention for equalizing charge states of a plurality of electrochemical energy storage cells of an electrochemical energy storage device comprises: - at least one compensating resistor for converting electrical energy into heat; - at least one switch for electrically connecting the compensating resistor in parallel to at least one of the electrochemical energy storage cells; - at least one heat conduction device for heat transfer of the generated heat by means of heat conduction; - at least one heat transport device for transporting the generated heat by means of a heat transport medium; - a control unit for determining charge states of the plurality of electrochemical energy storage cells, for controlling the switch and / or the heat transport device, and which is configured to carry out the steps of the method for equalizing charge states according to claim 1.

[0011] The heat conducting device comprises at least partially a material with high thermal conductivity, preferably made of a metal with low electrical resistance, in particular copper or aluminum.

[0012] The heat conduction device and / or the heat transport device enable an energy storage device-internal heat transfer and / or heat transport between the compensating resistor and other elements, for example a desiccant, seals, of the electrochemical energy storage device.

[0013] The heat transfer device comprises a temperature control body, preferably a temperature control body with temperature control fins. The temperature control body is a body that can be used for cooling. The temperature control fins increase the surface area required for heat transfer between the body and a heat transfer medium.

[0014] The heat transport device has a pumping device for supplying and / or removing the heat transport medium.

[0015] The pumping device includes a fan and / or a pump.

[0016] The heat transfer medium comprises a liquid medium, for example a liquid, and / or a gaseous medium, for example a gas. The gas is preferably ambient air of the electrochemical energy storage device and / or air, in particular conditioned air, from a passenger compartment of an electrically powered vehicle.

[0017] Advantageously, the method according to the invention for equalizing charge states and / or the device according to the invention for equalizing charge states is used in electrochemical energy storage devices for electric vehicles, fuel cell vehicles, hybrid vehicles, plug-in hybrid vehicles, aircraft, pedelecs or e-bikes, for electric hand tools, as well as in stationary storage devices for storing, in particular, electrical energy generated from renewable sources. Short description of the characters

[0018] Embodiments of the invention are illustrated in the drawing and explained in more detail in the following description.

[0019] They show: Fig. 1 is a flowchart of a first embodiment of the method according to the invention; and Fig. 2 a schematic representation of an embodiment of the device according to the invention.

[0020] Detailed description of the implementation examples

[0021] The same reference numerals denote the same device components in all figures.

[0022] Fig. 1 shows a flowchart of a first embodiment of the method (100) according to the invention.

[0023] In step 101, charge states of a plurality of electrochemical energy storage cells of an electrochemical energy storage device are detected, for example by means of voltage sensors which detect an electrical voltage of the electrochemical energy storage cells.

[0024] In step 102, the determined charge states are compared with specified target charge states.

[0025] If the determined charge levels exceed the specified target charge levels, the method continues in step 103, and at least one switch for electrically connecting at least one compensating resistor in parallel to at least one of the electrochemical energy storage cells is activated depending on the comparison. Otherwise, the method continues in step 101.

[0026] In step 104, the electrochemical energy storage cells, which have a significantly higher state of charge, are discharged by means of the at least one balancing resistor, whereby electrical energy is converted into heat.

[0027] In step 105, a heat transport device is controlled for heat transport of the generated heat by means of a heat transport medium in order to reuse the heat generated by the compensating resistor for maintenance purposes, in particular heating a desiccant within the electrochemical energy storage device, heating seals of the electrochemical energy storage device against corrosive creep and / or temperature-activated change opening of the electrochemical energy storage device.

[0028] Fig. 2 shows a schematic representation of an embodiment of the device 200 according to the invention for equalizing charge states of a plurality of electrochemical energy storage cells 202 of an electrochemical energy storage device 201.

[0029] The device 200 comprises a plurality of compensating resistors 203, which can be electrically connected in parallel to the electrochemical energy storage cells 202 by means of switches 204.

[0030] Furthermore, heat conduction devices 205 are thermally connected to each compensating resistor 203 in order to transfer the heat generated by the compensating resistors 203 by means of heat conduction.

[0031] Advantageously, by reducing heat losses and reusing energy, less cooling effort and lower requirements for the thermal resistance of the structure can be achieved.

[0032] In the illustrated embodiment, the compensating resistors 203 are positioned as close as possible to the heat conduction devices 205, since electrical conduction is subject to lower transmission losses than heat conduction or heat transport.

[0033] At least one heat transport device 206 is thermally connected to the heat conduction devices 205 in order to transport the heat generated by the compensating resistors 203 to further elements of the electrochemical energy storage device 201 by means of a heat transport medium.

[0034] The need to equalize the charge states of a plurality of electrochemical energy storage cells 202 of an electrochemical energy storage device 201 increases over the course of its service life. Furthermore, the maintenance requirement of the electrochemical energy storage device 201 also increases over its service life. By reusing the generated heat for maintenance purposes, in particular heating a desiccant within the electrochemical energy storage device 201, heating seals of the electrochemical energy storage device 201 to prevent corrosive creep, and / or temperature-activated opening of the electrochemical energy storage device 201, the service life of the electrochemical energy storage device can advantageously be extended.

[0035] Due to the heating of the interior of a housing of the electrochemical energy storage device 201 by the generated heat, the air's capacity to absorb additional water initially increases. As soon as this water is present in excess and released into the air, the absolute humidity within the housing increases. Temperature-activated opening of a valve enables air exchange with the ambient air of the housing, which reduces the absolute humidity within the housing. Upon cooling, the valve can be closed again, and the electrochemical energy storage device 201 is protected from penetrating foreign substances. By reducing the absolute humidity, condensation inside the housing is less likely to occur when the temperature drops.

[0036] A control unit 207 determines charge states of the plurality of electrochemical energy storage cells 202 and controls the switches 204 and the heat transport device 206. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2021 / 399553 A1

[0004] US 9,172,258

[0005]

Claims

[1] Method (100) for equalizing charge states of a plurality of electrochemical energy storage cells (202) of an electrochemical energy storage device (201), comprising the following steps: a) (101) determining charge states of the plurality of electrochemical energy storage cells (202); b) (102) comparing the determined charge levels with specified target charge levels; c) (103) controlling at least one switch (204) for electrically connecting at least one compensating resistor (203) in parallel to at least one of the electrochemical energy storage cells (202) as a function of the comparison; d) (104) discharging electrochemical energy storage cells (202) which have a significantly higher state of charge by means of the at least one compensating resistor (203) for converting electrical energy into heat; e) (105) controlling a heat transport device (206) for heat transport of the generated heat by means of a heat transport medium in order to reuse the heat generated by the compensating resistor (203) for maintenance purposes, in particular heating a desiccant within the electrochemical energy store (201), heating seals of the electrochemical energy store (201) against corrosive creep and / or temperature-activated change opening of the electrochemical energy store (201). [2] Device (200) for equalizing charge states of a plurality of electrochemical energy storage cells (202) of an electrochemical energy storage device (201), comprising: - at least one compensating resistor (203) for converting electrical energy into heat; - at least one switch (204) for electrically connecting the compensating resistor (203) in parallel to at least one of the electrochemical energy storage cells (202); - at least one heat conduction device (205) for heat transfer of the generated heat by means of heat conduction; - at least one heat transport device (206) for transporting the generated heat by means of a heat transport medium; - a control unit (207) for determining charge states of the plurality of electrochemical energy storage cells (202), for controlling the switch (204) and / or the heat transport device (206), and which is configured to carry out the steps of the method for equalizing charge states according to claim 1. [3] Device according to claim 2, wherein the heat conducting device (205) at least partially comprises a material with high thermal conductivity, preferably made of a metal with low electrical resistance, in particular copper or aluminum. [4] Device according to one of claims 2 or 3, wherein the heat conducting device (205) and / or the heat transport device (206) enable an energy storage internal heat transfer and / or heat transport between the compensating resistor (203) and further elements of the electrochemical energy storage device (201). [5] Device according to one of the preceding claims 2 to 4, wherein the heat transport device (206) comprises a tempering body, preferably a tempering body with tempering ribs. [6] Device according to one of the preceding claims 2 to 5, wherein the heat transport device (206) has a pumping device for supplying and / or removing the heat transport medium. [7] Device according to one of the preceding claims 2 to 6, wherein the pumping device comprises a fan and / or a pump. [8] Device according to one of the preceding claims 2 to 7, wherein the heat transport medium comprises a liquid medium and / or a gaseous medium. [9] Use of a method for equalising charge states according to claim 1 and / or a device for equalising charge states according to one of claims 2 to 8 in electrochemical energy storage devices for electric vehicles, fuel cell vehicles, hybrid vehicles, plug-in hybrid vehicles, aircraft, pedelecs or e-bikes, for electric hand tools, as well as in stationary storage devices for storing, in particular, electrical energy generated from renewable sources.

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