Battery low-temperature heating circuit and control device

Abstract

According to the battery low-temperature heating circuit and the control device provided by the utility model, the battery can be automatically heated according to the temperature of the battery module and related voltage information, so that the battery can work at a proper temperature, and the problems of low activity and poor charging performance of the existing battery at a low temperature are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a battery low-temperature heating circuit, method and control device. Background Art

[0002] Since the use of battery cells at low temperatures will reduce their lifespan and may pose a series of risks, with the development of energy storage new energy technologies, how to use energy storage battery systems at low temperatures has become the focus of research. Without consuming battery energy, increasing the safety of the battery heating function. Specifically, the batteries produced by the prior art have the following problems:

[0003] 1. The battery has low activity and poor charging performance at low temperatures, and there is a risk of lithium plating;

[0004] 2. Heating the battery consumes the energy of the battery itself;

[0005] 3. In a low-temperature environment, when the power supply heats the battery, the battery may be charged;

[0006] 4. When the external power is lower than the rated power of the heating device, heating cannot be performed;

[0007] 5. A single control loop, and the failure of this loop may cause the battery to continue heating and pose a danger;

[0008] 6. The abnormal detection function of the heating loop device and the heating failure detection function are not perfect. Summary of the Utility Model

[0009] The purpose of the utility model is to provide a battery low-temperature heating circuit, method and control device to solve the problems that the batteries produced by the prior art have low activity, poor charging performance and the risk of lithium plating at low temperatures.

[0010] First of all, the utility model provides a battery low-temperature heating circuit, which includes a first branch and a second branch. The first branch includes a first switch, and the second branch includes a second switch and a heating film connected in series. Two ends of the first branch are respectively connected to one end of the battery module and one end of the second branch, and the other end of the second branch is connected to the other end of the battery module and one end of the power supply, and the other end of the power supply is connected to one end of the second branch.

[0011] Furthermore, the first branch further includes a first diode, and the first diode is connected in parallel at both ends of the first switch; or / and, the second branch further includes a third switch, and the third switch is connected in series with the second switch and the heating film; or / and, it further includes a fourth switch, and the fourth switch is used to connect or disconnect the power supply.

[0012] Further, the circuit further includes a fuse, and the fuse is connected in series in the first branch, and / or between the second branch, and / or the power supply and the second branch.

[0013] Further, the first switch and the second switch are MOSFET, IGBT, relay or triode.

[0014] Further, the first diode and the first switch are discrete devices or integrated devices.

[0015] Further, the heating film is attached to the battery module.

[0016] Further, the power supply is a PCS / direct current source / charger.

[0017] Further, it further includes PV and / or the power grid for supplying power to the power supply.

[0018] Furthermore, the present invention also discloses a battery low-temperature heating control device for controlling the battery low-temperature heating circuit, including a controller, a comparator, and an AND gate. The controller is used to receive the battery module voltage and battery module temperature signals, and respectively output corresponding battery reference voltage and first temperature signal. The positive and negative input terminals of the comparator are respectively used to input the power supply voltage and the battery reference voltage. The input terminal of the AND gate is used to input the output of the comparator and the first temperature signal. The output of the AND gate is used to control the on / off of the second switch; the controller is further used to output a first drive signal for controlling the on / off of the first switch.

[0019] Further, the control device further includes a current acquisition unit for acquiring the current flowing through the second branch.

[0020] The above-mentioned battery low-temperature heating circuit and control device can automatically heat the battery according to the battery module temperature and related voltage information, so that the battery can work at a suitable temperature, and solves the problems that the existing battery has low activity and poor charging performance at low temperature. Description of the Drawings

[0021] Figure 1 It is the battery low-temperature heating circuit of the first embodiment of the present invention.

[0022] Figure 2 It is the battery low-temperature heating circuit of the second embodiment of the present invention.

[0023] Figure 3 It is the battery low-temperature heating circuit of the third embodiment of the present invention.

[0024] Figure 4The battery low-temperature heating circuit according to the fourth embodiment of the present utility model.

[0025] Figure 5 The battery low-temperature heating circuit according to the fifth embodiment of the present utility model.

[0026] Figure 6 The battery low-temperature heating circuit according to the sixth embodiment of the present utility model.

[0027] Figure 7 The battery low-temperature heating circuit according to the seventh embodiment of the present utility model.

[0028] Figure 8 The battery low-temperature heating circuit according to the eighth embodiment of the present utility model.

[0029] Figure 9 The battery low-temperature heating control device according to an embodiment of the present utility model.

[0030] Figure 10 The battery low-temperature heating control device according to another embodiment of the present utility model.

[0031] Figure 11 The battery low-temperature heating control device according to another embodiment of the present utility model.

[0032] Figure 12 The battery low-temperature heating control device according to another embodiment of the present utility model.

[0033] Description of main component symbols:

[0034] Heating film 11 First switch 40 Third switch 12 First diode 41 Second switch 13 Fourth switch 50 Controller 21 Battery module 100 Comparator 22 Power supply 200 AND gate 23

[0035] The following specific embodiments will further illustrate the present utility model in conjunction with the above-mentioned drawings. Specific embodiments

[0036] For ease of understanding of the present utility model, the present utility model will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present utility model are given in the drawings. However, the present utility model can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present utility model more thorough and comprehensive.

[0037] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this utility model belongs. The terms used in the description of this utility model herein are only for the purpose of describing specific embodiments and are not intended to limit this utility model. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0039] Please refer to Figure 1 , a battery low-temperature heating circuit provided by the first embodiment of this utility model is used to heat the battery when the battery is at low temperature. It includes a first branch and a second branch. The first branch includes a first switch 40. The second branch includes a second switch 13 and a heating film 11 connected in series. Two ends of the first branch are respectively connected to one end of a battery module 100 and one end of the second branch. The other end of the second branch is connected to the other end of the battery module 100 and one end of a power supply 200. The other end of the power supply 200 is connected to one end of the second branch. Among them, the first switch 40 and the second switch 13 can be MOSFET, IGBT, relay, triode or other controllable switch tubes.

[0040] Please refer to Figure 2 , a battery low-temperature heating circuit provided by the second embodiment of this utility model, the difference from Figure 1 the embodiment is that, Figure 2 in the embodiment, the first branch further includes a first diode 41, and the first diode 41 is connected in parallel at both ends of the first switch 40. Among them, the parallel-connected first diode 41 and the first switch 40 can be discrete devices or integrated devices. When the power supply 200 is a PCS (or a DC source, or a charger, or other controllable power supply) and it is necessary to detect that the battery module 100 is connected to the power supply 200 for the power supply 200 to work, the first diode 41 is required; because if there is no first diode 41, the battery module 100 and the power supply 200 form an open circuit, and the power supply 200 thinks that the battery module 100 is not connected to it, and the power supply 200 will not work (that is, it will not supply energy to the heating film 11). Among them, PCS is a power conversion system, and its full English name is Power Conversion System.

[0041] Please refer to Figure 3 , a battery low-temperature heating circuit provided by the third embodiment of this utility model, the difference from Figure 1 the embodiment is that, Figure 3In the embodiment, the second branch further includes a third switch 12, and the third switch 12 is connected in series with the second switch 13 and the heating film 11; the disconnection of the second switch 13 and the third switch 12 from the second branch forms redundant control, improving the reliability of the circuit. For example, it can avoid the situation where the battery low-temperature heating circuit needs to stop heating, but due to the failure of the second switch 13 or the third switch 12 (such as normally closed), the second branch cannot be disconnected and continues to heat, thus triggering a safety accident (such as battery explosion).

[0042] Please refer to Figure 4 , a battery low-temperature heating circuit provided by the fourth embodiment of the present invention, which is different from the Figure 1 embodiment in that Figure 4 in the embodiment, it further includes a fourth switch 50, and the fourth switch 50 is used to control the access or disconnection of the power supply 200. Both ends of the fourth switch 50 are connected to the other end of the power supply 200 and one end of the second branch respectively. Or in other embodiments, both ends of the fourth switch 50 are connected to one end of the power supply 200 and the other end of the second branch respectively.

[0043] Please refer to Figure 5 , a battery low-temperature heating circuit provided by the fifth embodiment of the present invention, which is different from the Figure 3 embodiment in that Figure 5 in the embodiment, the first branch further includes a first diode 41, and the first diode 41 is connected in parallel with both ends of the first switch 40. Figure 5 The function of the first diode 41 in the embodiment is the same as that in the Figure 2 embodiment, and will not be elaborated here. Among them, the parallel-connected first diode 41 and the first switch 40 can be discrete devices or synthetic devices (for example, the first diode 41 and the first switch 40 can be synthesized into a MOSFET with a body diode).

[0044] Please refer to Figure 6 , a battery low-temperature heating circuit provided by the sixth embodiment of the present invention, which is different from the Figure 3 embodiment in that Figure 6 in the embodiment, it further includes a fourth switch 50, and the fourth switch 50 is used to control the access or disconnection of the power supply 200. Both ends of the fourth switch 50 are connected to the other end of the power supply 200 and one end of the second branch respectively. Or in other embodiments, both ends of the fourth switch 50 are connected to one end of the power supply 200 and the other end of the second branch respectively.

[0045] Please refer to Figure 7 , a battery low-temperature heating circuit provided by the seventh embodiment of the present invention, which is different from the Figure 2 embodiment in that Figure 7In the embodiment, a fourth switch 50 is further included. The fourth switch 50 is used to control the connection or disconnection of the power supply 200. Two ends of the fourth switch 50 are respectively connected to the other end of the power supply 200 and one end of the second branch. Or in other embodiments, two ends of the fourth switch 50 are respectively connected to one end of the power supply 200 and the other end of the second branch.

[0046] Please refer to Figure 8 , a battery low-temperature heating circuit provided by the eighth embodiment of the present invention, which is different from Figure 7 the embodiment in that Figure 8 in the embodiment, the second branch further includes a third switch 12. The third switch 12 is connected in series with the second switch 13 and the heating film 11. Figure 8 The function of the third switch 12 in the embodiment is the same as that in Figure 3 the embodiment, and will not be described in detail.

[0047] In order to protect the circuit and devices / components from problems such as current overload and short circuit, in other embodiments of the battery low-temperature heating circuit, a fuse can be connected in series. For example, a fuse can be connected in series in the first branch, or / and, a fuse can be connected in series in the second branch in the embodiments herein, or / and, a fuse can be connected in series between the power supply 200 and the second branch, and so on.

[0048] In other embodiments, the aforementioned battery low-temperature heating circuit further includes a PV or / and a power grid. The power supply 200 can be powered by the PV or / and the power grid, where PV is a solar photovoltaic panel.

[0049] In other embodiments, the heating film 11 in the aforementioned battery low-temperature heating circuit is attached to the battery module 100, and the battery is heated by heat conduction to increase the temperature of the battery.

[0050] A battery low-temperature heating method is applied to the battery low-temperature heating circuit described herein. The method includes:

[0051] When the temperature of the battery module 100 is lower than a first preset temperature and the voltage difference between the power supply 200 and the battery module 100 is greater than a first preset voltage (i.e., Vs - Vb > V1, where Vs is the voltage of the power supply 200, Vb is the voltage of the battery module 100, and V1 is the first preset voltage; V1 can be a preset ratio of Vb, for example, V1 can be 5% - 20% of Vb, or other preset ratios), control a path to be formed between the power supply 200 and the heating film 11 to heat the heating film 11. Among them, the first preset temperature can be taken from the range of 0.5°C - 6°C, or other values can be selected according to actual needs / requirements.

[0052] When the voltage difference between the power supply 200 and the battery module 100 is less than or equal to a second preset voltage (i.e., Vs - Vb ≤ V2, where V2 is the second preset voltage; V2 can be a preset ratio of Vb, for example, V2 can be 0% - 10% of Vb, or other preset ratios; it can be understood that V2 ≤ V1), control an open circuit to be formed between the power supply 200 and the heating film 11, and stop heating the heating film 11.

[0053] Since the voltage Vs of the power supply 200 is always greater than the voltage Vb of the battery module 100 during the heating of the heating film, the energy required for the heating process only comes from the power supply 200 and will not come from the battery module 100, so the energy of the battery module 100 is not consumed during heating.

[0054] When the temperature of the battery module 100 is higher than a second preset temperature, control an open circuit to be formed between the power supply 200 and the heating film 11, and stop heating the heating film 11; wherein, the second preset temperature can be taken from the range of 9°C - 15°C, or other values can also be selected according to actual needs / requirements.

[0055] In one embodiment, the temperature of the battery module 100 can be obtained by detecting with a thermistor attached to the battery module 100.

[0056] In one embodiment, the foregoing method further includes, before heating the heating film 11, disconnecting the connection between the battery module 100 and the power supply 200 (for example, in the embodiments of this article, the connection between the battery module 100 and the power supply 200 can be disconnected by controlling the first switch 40 to open), so that the power supply 200 stops charging the battery module 100 during heating.

[0057] The foregoing "control a path to be formed between the power supply 200 and the heating film 11" can be achieved by controlling corresponding switches for different embodiments. For example, Figure 1 / Figure 2 For the circuit of the embodiment, by controlling the second switch 13 to close, a path can be formed between the power supply 200 and the heating film 11. For Figure 3 / Figure 5 For the circuit of the embodiment, by controlling the second switch 13 and the third switch 12 to close, a path can be formed between the power supply 200 and the heating film 11. For Figure 4 / Figure 7 For the circuit of the embodiment, by controlling the second switch 13 and the fourth switch 50 to close, a path can be formed between the power supply 200 and the heating film 11. For Figure 6 / Figure 8The circuit of the embodiment can form a path between the power supply 200 and the heating film 11 by controlling the closing of the second switch 13, the third switch 12, and the fourth switch 50.

[0058] The aforementioned "control the formation of an open circuit between the power supply 200 and the heating film 11" can be achieved by controlling the corresponding switch for different embodiments. For example, Figure 1 / Figure 2 The circuit of the embodiment can form an open circuit between the power supply 200 and the heating film 11 by controlling the disconnection of the second switch 13. Figure 3 / Figure 5 The circuit of the embodiment can form an open circuit between the power supply 200 and the heating film 11 by controlling the disconnection of the second switch 13 or / and the third switch 12. Figure 4 / Figure 7 The circuit of the embodiment can form an open circuit between the power supply 200 and the heating film 11 by controlling the disconnection of the second switch 13 or / and the fourth switch 50. Figure 6 / Figure 8 The circuit of the embodiment can form an open circuit between the power supply 200 and the heating film 11 by controlling the disconnection of the second switch 13 or / and the third switch 12 or / and the fourth switch 50.

[0059] In one embodiment, the aforementioned method further includes that when the voltage difference between the power supply 200 voltage and the battery module 100 is less than or equal to the second preset voltage, boost the voltage of the power supply 200 (through PV or / and the power grid, not shown in the figure) until the voltage difference between the power supply 200 voltage and the battery module 100 is greater than the first preset voltage, and then re-heat the heating film 11 (of course, at this time, the heating will only occur when the temperature of the battery module 100 is lower than the first preset temperature).

[0060] In one embodiment, the aforementioned method further includes that before the power supply 200 provides energy, detect the switch adhesion of the second branch. For example, send a turn-off signal to the second branch. If it is detected that there is current flowing through the second branch, it means that the switch on the second branch has adhesion, and do not start heating the heating film.

[0061] The aforementioned "send a turn-off signal to the second branch" can have different implementation manners for different embodiments. For example, Figure 1 / Figure 4 The circuit of the embodiment can close the first switch 40 and send a turn-off signal to the second switch 13. For the circuit of the 2 / 7 embodiment, the turn-off signal can be sent to the second switch 13. Figure 3 / Figure 6The circuit of the embodiment can close the first switch 40 and send a turn-off signal to the second switch 13 and the third switch 12. Figure 5 / Figure 8 The circuit of the embodiment can send a turn-off signal to the second switch 13 and the third switch 12.

[0062] In one embodiment, the foregoing method further includes performing overcurrent / open circuit detection on the second branch before the power supply 200 provides energy. For example, a closing signal is sent to the second branch. If it is detected that the current in the second branch is too large (for example, greater than a first preset current, and the first preset current can be 120%-130% of the rated current when the power supply 200 provides energy to heat the heating film 11, or other values can be selected according to actual needs / requirements), it indicates that the second branch is overcurrent (for example, caused by a short circuit of the heating film). If it is detected that the current in the second branch is too small (for example, less than a second preset current, and the second preset current can be 75-85% of the rated current when the power supply 200 provides energy to heat the heating film 11, or other values can be selected according to actual needs / requirements), it indicates that the second branch is open (for example, caused by an open circuit of the heating film or a fault of the second branch switch), and the heating of the heating film is not started.

[0063] For the foregoing "sending a closing signal to the second branch", different implementation manners may be adopted in different embodiments. For example, Figure 1 / Figure 4 The circuit of the embodiment can close the first switch 40 and send a closing signal to the second switch 13. For the circuit of the 2 / 7 embodiment, a closing signal can be sent to the second switch 13. Figure 3 / Figure 6 The circuit of the embodiment can close the first switch 40 and send a closing signal to the second switch 13 and the third switch 12. Figure 5 / Figure 8 The circuit of the embodiment can send a closing signal to the second switch 13 and the third switch 12.

[0064] The foregoing detection of switch adhesion / overcurrent / open circuit of the second branch is collectively referred to as fault detection of the second branch.

[0065] In one embodiment, the foregoing method further includes that the power supply 200 provides energy to heat the heating film 11, and the heat of the heating film 11 is conducted to the battery module 100, so that the temperature of the battery module rises. According to the conduction duty ratio of the second switch 13, the heating power of the heating film 11 is obtained, and in combination with the heat conduction efficiency from the heating film 11 to the battery module 100, the first time t1 required for the battery module 100 to reach the second temperature T2 is calculated. If the first time t1 arrives and the battery module 100 does not reach the second temperature T2, it is considered that the heating is abnormal / faulty, and the second switch 13 is disconnected.

[0066] The present utility model also discloses a battery low-temperature heating control device, as Figure 9 shown, applied to the battery low-temperature heating circuit of the foregoing Figure 1 / Figure 2 embodiment, including a controller 21, a comparator 22, and an AND gate 23. After the voltage Vb of the battery module 100 is input to the controller 21, a battery reference voltage Vr is generated. The voltage Vs of the power supply 200 and the battery reference voltage Vr are respectively used as the positive input terminal and the negative input terminal of the comparator 22. The comparator 22 outputs a first voltage signal Drt. The temperature signal Vbt of the battery module 100 outputs a first temperature signal Drt after passing through the controller. The first voltage signal Drt and the first temperature signal Drt are used as the inputs of the AND gate 23. The output of the AND gate 23, that is, the second drive signal Dr13, is used to control the on-off of the second switch 13.

[0067] When the voltage Vs of the power supply 200 is greater than the battery reference voltage Vr, the first voltage signal Drt output by the comparator 22 is at a high level. When the temperature signal Vbt of the battery module 100 indicates that the temperature of the battery module 100 is lower than the first preset value, the first temperature signal Drt is at a high level, so that the output of the AND gate 23, that is, the second drive signal Dr13, is at a high level, thereby turning on the second switch 13. When the voltage Vs of the power supply 200 is less than the battery reference voltage Vr, or / and, the temperature signal Vbt of the battery module 100 indicates that the temperature of the battery module 100 is higher than the second preset temperature, the output of the AND gate 23, that is, the second drive signal Dr13, will be at a low level, thereby turning off the second switch 13.

[0068] In one embodiment, the battery reference voltage Vr is the sum of the voltage Vb of the battery module 100 and a first preset voltage V1, that is, Vr = Vb + V1.

[0069] In one embodiment, the battery reference voltage Vr is the sum of the voltage Vb of the battery module 100 and a second preset voltage V2, that is, Vr = Vb + V2.

[0070] The first drive signal Dr40 output by the controller 21 is used to control the on-off of the first switch 40; when it is necessary to heat the heating film (for example, the controller 21 receives the temperature signal Vbt of the battery module 100 indicating that the temperature of the battery module 100 is lower than the first preset value), before the second switch 13 is turned on, the first drive signal Dr40 controls the first switch 40 to be turned off; when it is necessary to charge the battery module 100 or the battery module 100 needs to discharge, the first switch 40 is turned on, and the battery module 100 is charged through the power supply 200.

[0071] In one embodiment, the voltage Vs of the power supply 200 and the voltage Vb of the battery module 100 can both be obtained through a voltage acquisition unit (such as an operational amplifier), and the temperature signal Vbt of the battery module 100 can be obtained through a temperature sampling unit (such as a thermistor); since voltage sampling and temperature sampling are both conventional techniques in the art, they will not be elaborated herein.

[0072] The present utility model also discloses another battery low-temperature heating control device, as Figure 10 shown, applied to the battery low-temperature heating circuit of the foregoing Figure 3 / Figure 5 embodiment, the difference between it and the control device of the embodiment shown in Figure 9 is that the control device of the Figure 10 embodiment further includes a third drive signal Dr12 for controlling the on / off of the third switch 12. In one embodiment, the third drive signal Dr12 is the same as the first temperature signal Drt. When the temperature signal Vbt of the battery module 100 indicates that the temperature of the battery module 100 is lower than the first preset value, the third drive signal Dr12 is at a high level to control the third switch 12 to conduct; when the temperature signal Vbt of the battery module 100 indicates that the temperature of the battery module 100 is higher than the second preset temperature, the third drive signal Dr12 is at a low level to control the third switch 12 to disconnect.

[0073] The present utility model also discloses another battery low-temperature heating control device, as Figure 11 shown, applied to the battery low-temperature heating circuit of the foregoing Figure 4 / Figure 7 embodiment, the difference between it and the control device of the embodiment shown in Figure 9 is that the control device of the Figure 11 embodiment further includes a fourth drive signal Dr50 for controlling the on / off of the fourth switch 50.

[0074] The present utility model also discloses another battery low-temperature heating control device, as Figure 12 shown, applied to the battery low-temperature heating circuit of the foregoing Figure 6 / Figure 8 embodiment, the difference between it and the control device of the embodiment shown in Figure 10 is that the control device of the Figure 12 embodiment further includes a fourth drive signal Dr50 for controlling the on / off of the fourth switch 50.

[0075] Figure 11 、 Figure 12In the control device of the embodiment, when the power supply 200 needs to heat the heating film 11, or the power supply 200 needs to charge the battery module 100, or the battery module 100 needs to charge the power supply 200, etc., the fourth driving signal Dr50 controls the fourth switch 50 to conduct; when it is necessary to stop the power supply 200 from heating the heating film 11, or stop the power supply 200 from charging the battery module 100, or stop the battery module 100 from charging the power supply 200, etc., the fourth driving signal Dr50 controls the fourth switch 50 to turn off.

[0076] In one embodiment, the foregoing control device further includes a current acquisition unit (not shown in the figure), and the current acquisition unit is used to acquire the current flowing through the second branch (see the corresponding description in the foregoing method embodiment).

[0077] In one embodiment, the foregoing control device further includes a second switch 13 state detection unit (not shown in the figure), which is used to detect the on / off state of the second switch 13 and obtain its conduction duty cycle. For example, the second switch 13 state detection unit may be a voltage detection unit, which is used to detect the voltage across the second switch 13, and obtain whether the second switch 13 is conducting or off according to the detected voltage signal, so as to obtain the conduction duty cycle of the second switch 13.

[0078] The above battery low-temperature heating circuit, method and control device collect the temperature information and relevant voltage information (power supply voltage, battery voltage) of the battery, and then control the on / off of the corresponding switch to automatically heat the battery module 100, so that the battery module 100 can work at a suitable temperature, solving the problems that the existing battery has low activity and poor charging performance at low temperature.

[0079] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims

1. A battery low temperature heating circuit, characterized in that: It includes a first branch and a second branch. The first branch includes a first switch. The second branch includes a second switch and a heating film connected in series. Two ends of the first branch are respectively connected to one end of a battery module and one end of the second branch. The other end of the second branch is connected to the other end of the battery module and one end of a power source. The other end of the power source is connected to one end of the second branch.

2. The battery low temperature heating circuit according to claim 1, characterized in that: The first branch also includes a first diode, which is connected in parallel to both ends of the first switch; or / and, the second branch also includes a third switch, which is connected in series with the second switch and the heating film; or / and, also includes a fourth switch, which is used to connect or disconnect the power supply.

3. The battery low temperature heating circuit according to claim 1 or 2, characterized in that: It also includes a fuse, which is connected in series with the first branch, or / and the second branch, or / and between the power supply and the second branch.

4. The battery low temperature heating circuit according to claim 1 or 2, characterized in that: The first switch and the second switch are MOSFET, IGBT, relay or triode.

5. The battery low temperature heating circuit according to claim 2, characterized in that: The first diode and the first switch are discrete devices or composite devices.

6. The battery low temperature heating circuit according to claim 1 or 2, characterized in that: The heating film is attached to the battery module.

7. The battery low temperature heating circuit according to claim 1 or 2, characterized in that: The power source is a PCS / DC source / charger.

8. The battery low temperature heating circuit according to claim 1 or 2, characterized in that: It also includes PV and / or grid for supplying power to the power source.

9. A battery low temperature heating control device, used to control the battery low temperature heating circuit according to any one of claims 1 to 8, characterized in that: It includes a controller, a comparator, and an AND gate. The controller is used to receive the battery module voltage and the battery module temperature signal, and output the corresponding battery reference voltage and the first temperature signal respectively. The positive and negative input terminals of the comparator are used to input the power supply voltage and the battery reference voltage respectively. The input terminal of the AND gate is used to input the output of the comparator and the first temperature signal. The output of the AND gate is used to control the on-off of the second switch. The controller is also used to output a first drive signal for controlling the on-off of the first switch.

10. The battery low temperature heating control device according to claim 9, characterized in that: It also includes a current collection unit, which is used to collect the current flowing through the second branch.

Images