METHOD FOR COOLING A BATTERY AND COOLING SYSTEM

Abstract

A method for cooling a battery for an electrically powered aircraft, wherein the battery has battery cell(s) and a battery cooling device with a latent heat store. The method includes: A) transferring a first amount of heat from the battery cell to the latent heat store, causing a phase transition in the phase change material, B) removing the battery from the aircraft, C) establishing an operative connection of the battery cooling device to a cooling circuit of a separate second cooling device, D) passing a flow of a coolant through the cooling circuit, E) transferring a second amount of heat from the latent heat store to the coolant, thus causing a phase transition to occur in the phase change material, and F) disconnecting the battery cooling device from the cooling circuit. Step E and/or F are carried out at least partially simultaneously with a charging process of the battery.

Claims

1. A method for cooling a battery (3) for an electrically powered aircraft (1), the battery (3) comprising a battery cell (5) and a battery cooling device with at least one latent heat store (19), the method comprising the following steps: A) transferring a first amount of heat from the battery cell (5) to the latent heat store (19), causing a phase transition to occur in the phase change material of the latent heat store (19), B) removing the battery (3) from the aircraft (1), C) establishing an operative connection of the battery cooling device to a cooling circuit (27) of a separate second cooling device (26), D) passing a flow of a coolant (13) through the cooling circuit (27), E) transferring a second amount of heat from the latent heat store (19) to the coolant (13), causing a phase transition to occur in the phase change material of the latent heat store (19), and F) disconnecting the battery cooling device from the cooling circuit (27), wherein at least one of step D or step E take place at least partially simultaneously with a charging process of the battery (3).

2. The method as claimed in claim 1, wherein step E takes place after step D, and the operative connection of the battery cooling device to the cooling circuit (27) is improved by an inflow of the coolant in method step E.

3. The method as claimed in claim 1, wherein the cooling circuit (27) operates according to a counterflow principle.

4. The method as claimed in claim 1, wherein after the step C, the method further comprises inserting the battery (3) into a holder of a ground charging station (25) which allows simultaneous charging of the battery (3) and cooling of the latent heat store (19).

5. A cooling system (6) for cooling a battery cell (5) of an electrically powered aircraft (1), the cooling system (6) comprising: a battery cooling device configured to absorb a first amount of heat at least from the battery cell (5) during an electrical discharge process, the battery cooling device comprising at least one latent heat store (19) having a variable aggregate state; a separate second cooling device (26) which is thermally coupleable to the battery cooling device and is configured to receive a second amount of heat from the battery cooling device; and an electrical charging device for the battery cell (5) for electrically contacting and charging the battery cells (5) for the charging process of the battery cells (5).

6. The cooling system (6) as claimed in claim 5, wherein the phase change material of the latent heat store (19) of the battery cooling device is macroencapsulated in a carrier matrix.

7. The cooling system (6) as claimed in claim 5, wherein the phase change material of the latent heat store (19) of the battery cooling device comprises at least one of a sleeve around the battery cells, a plate of an at least partial housing around a plurality of battery cells, or at least one perforated plate.

8. The cooling system (6) as claimed in claim 5, wherein the phase change material of the latent heat store (19) is configure for a temperature range for heat generation of the battery cell (5) in an operating state in a range of 20° C. to 60° C.

9. The cooling system (6) as claimed in claim 5, further comprising a fire protection material located around the battery cells.

10. The cooling system (6) as claimed in claim 5, wherein the second cooling device (26) has at least one of a flexible hose (9) or a cooling plate which is finable with and passed through by a coolant (13).

11. The cooling system (6) as claimed in claim 5, wherein the second cooling device (26) is part of a stationary ground charging station (25) and the ground charging station (25) comprises an electrical charging device for the battery cell (5) and is configured to electrically contact the battery cells (5) for a charging process of the battery cell (5).

12. The cooling system (6) as claimed in claim 5, wherein the second cooling device (26) is part of a stationary ground charging station (25) and the ground charging station (25) comprises a holder for the battery (3) and is configured to connect the second cooling device (26) and the battery cooling device in a thermally conductive manner.

13. The cooling system (6) as claimed in claim 5, wherein the battery (3) comprises a busbar and the battery cell (5) is electrically conductively connected to the busbar.

14. The cooling system (6) as claimed in claim 13, wherein the battery cell (5) is electrically conductively connected to the busbar via at least one wire bond, the battery (3) comprises at least two battery cells (5) which are configured as cylindrical round cells (5) with a negatively polarized end face (N) and with a positively polarized end face (P), and the round cells (5) are geometrically oriented in a same way and are connected via the wire bond, on a same side of the battery cells.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Further preferred features and embodiments of the method according to the invention and of the cooling system according to the invention are explained below with reference to exemplary embodiments and the figures. These exemplary embodiments as well as any dimensions indicated are merely advantageous embodiments of the invention and are therefore not limiting. The figures show:

[0059] FIG. 1 an exploded view of the battery;

[0060] FIG. 2 a front sectional view of the battery;

[0061] FIG. 3 a cooling system according to the invention and a multicopter; and

[0062] FIG. 4 a schematic representation of a holder for the battery.

DETAILED DESCRIPTION

[0063] FIG. 1 shows an exploded view of the battery 3, which is shown in a sectional view in FIG. 2.

[0064] The battery cells 5 of the battery 3 are embodied as lithium-ion round cells and are arranged geometrically symmetrically.

[0065] The battery cells 5 are enclosed on the outer surfaces by sleeves 19. In the present case, the sleeves 19 are made of the phase change material of the latent heat store and a fire protection material. This creates direct thermal contact between the battery cells 5 and the latent heat stores 19.

[0066] The latent heat store is made in the present case of a composite material in which the phase change material is macroencapsulated in a carrier matrix. For example, materials such as paraffin compounds or ester compounds can be used as phase change material.

[0067] The fire protection material has a two-layer structure in which a first layer of the fire protection material in the form of a glass fiber layer is mechanically stable. The second layer of the fire protection material is made of hydrated minerals, in the present case water of crystallization.

[0068] The mechanically stable layer of the fire protection material prevents the battery cell from bursting open sideways in the event of overpressure during a thermal runaway of one of the battery cells. The second layer of the fire protection material, consisting of water of crystallization, serves to absorb heat released during the thermal runaway by the water contained in the layer being evaporated. During the phase transition of the water of crystallization, the temperature of the material can be kept constant so that adjacent battery cells are protected from overheating.

[0069] A first cell holder 20 and a second cell holder 21 are arranged above and below the battery cells. The cell holders 20, 21 serve to spatially fix the battery cells 5 in the housing of the battery 3 so that any forces acting on the battery cells 5 do not have to be supported by the sleeves 19.

[0070] A housing (not shown) is provided around the described components.

[0071] An electrically insulating layer 23 is provided to prevent the battery cells 5 from short-circuiting. A base plate 14 is arranged on the electrically insulating layer 23 as part of the battery housing. This layer is in contact with the cooling hose 9 in the second cooling device, see FIG. 4. Via the base plate 14 and the electrically insulating layer 23, the battery cells 5 and the material of the latent heat store 19 in contact with the battery cells can be brought into thermal contact with the second external cooling device. The base plate 14 and the electrically insulating layer 23 thus represent the thermal interface between the battery cooling device and the second separate cooling device.

[0072] FIG. 3 shows a cooling system with a ground charging station 25 and a multicopter 1. The cooling system extends to the battery cooling device, which is typically on board the multicopter 1 when in operation, and to the second separate external cooling device 26 in the ground charging station 25.

[0073] During flight operation, the battery 3 is discharged and heat is transferred to the latent heat store 19. When the aircraft is stopped, the battery 3 is removed from the aircraft 1 and inserted into the holder 24 of the ground charging station 25.

[0074] The charging process of the battery is used to return the “spent” latent heat store unit 19 to its initial state, i.e. to return the liquid/viscous phase change material of the latent heat store 19 to a solid aggregate state. For this purpose, the battery 3 is removed from the aircraft and contacted both electrically and thermally in the ground charging station 25.

[0075] For this purpose, the ground charging station 25 comprises the second cooling device 26. The second cooling device 26 has a cooling circuit 27 with a coolant tank 28 and the coolant 13 contained therein. A pump 29 delivers the coolant 13 through a heat exchanger 30 and via the inlet 31 into the flexible cooling hose (not shown). The cooling hose runs in a holder 24 (see FIG. 4) into which the batteries 3 are inserted from the aircraft. The heated coolant 13 re-enters the coolant tank 28 through an outlet 32.

[0076] To improve the cooling effect of the flexible cooling hose, it can be subjected to a high internal pressure. This causes the cooling hose to expand and exerts a correspondingly high contact pressure on the components to be cooled, in particular the thermal interface in the form of the base plate 14 of the battery 3.

[0077] The cooling hose is filled with the coolant only after the battery 3 has been inserted into the holder 24.

[0078] At the same time, the battery cells of the battery 3 are electrically contacted with a stationary energy storage unit 11 via the connection 33 and are charged. The energy storage unit 11 is connected to a generator 34, by which it can be charged after or during the charging process.

[0079] In accordance with the invention, the cooling system shown reverses a phase transition of a heated latent heat store by means of active cooling. In this process, the liquid/viscous latent heat stores (19) are returned to a solid aggregate state.

[0080] Once the charging process has been completed and the latent heat store has been successfully restored to functionality, the battery 3 can be removed from the ground charging station 25 and is ready for use again.

[0081] FIG. 4 shows a holder 24 for the battery 3, as usually provided in a ground charging station 25 (FIG. 3). The holder 24 comprises a plurality of holding rails into which a plurality of batteries 3 can be inserted. Between the batteries there are provided cooling hoses 9, through which coolant can flow. The cooling hoses 9 are in thermal contact with the base plates 14 of the batteries 3 in the holding rails