A method for charging and automatically calibrating the SOC of a battery pack through a discharge port

Abstract

The application discloses a method for charging and automatically calibrating the SOC of a battery pack through a discharging port, comprising the following steps: presetting the output voltage, current and charging cutoff condition of a charging device; connecting the charging device and the battery pack, collecting and reporting the highest voltage V of the single cell in the battery pack by the BMS (A) in the battery pack in real time max ; judging whether the charging device meets the charging cutoff condition, stopping the output when the condition is met, and at this time, the battery pack is in the full charge / full power state; externally connecting the BMS (B) and monitoring the V sent by the BMS (A) through the BMS (B) max ; when the V max reaches the charging cutoff voltage V cut‑off , sending a calibration SOC=100% instruction to the BMS (A); after receiving the instruction in step S4, the BMS (A) updates the SOC to 100% and saves it. Without plugging in the gun for charging, the method of charging the batch battery pack through the discharging port in a protocol-free manner is adopted, and the SOC of the battery pack is automatically calibrated when it is fully charged through the externally connected calibration device, so that the charging and power calibration of the batch battery pack when leaving the factory are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of battery pack SOC calibration, and particularly relates to a method for charging through a discharging port and automatically calibrating the SOC of a battery pack. BACKGROUND

[0002] When a battery pack is delivered from a factory, the battery pack needs to be charged to ensure that the battery capacity is at 100%. When the battery pack is charged by using a charger, the BMS collects real-time data of each battery cell and exchanges information with the charger according to a predetermined protocol. Generally, when the voltage of a certain battery reaches the maximum allowable charging voltage of the battery cell, the BMS judges and calibrates that the SOC of the battery pack reaches 100%.

[0003] As shown in FIG. 1, the battery pack is charged by using a charger, and different chargers need to be selected according to charging protocols. Since the requirements of various vehicle manufacturers are different, the charging protocols are also quite different. If a charger is provided for each battery pack with a protocol, the efficiency is low and the cost is high. Therefore, the number of existing chargers cannot simultaneously meet the delivery requirements of a large number of battery packs with different charging protocols. Figure 1

[0004] The present patent combines the battery charging and discharging characteristics and the logic of BMS charging and discharging control, and does not use plug-in charging, but uses a protocol-free charging method through the discharging port to charge the batch battery pack, and automatically calibrates the SOC of the battery pack when fully charged through an external calibration device, thereby solving the charging and capacity calibration problems of batch battery packs. SUMMARY

[0005] In order to make up for the deficiencies of the prior art, the present application provides a technical scheme of a method for charging through a discharging port and automatically calibrating the SOC of a battery pack.

[0006] The method for charging through a discharging port and automatically calibrating the SOC of a battery pack comprises the following steps:

[0007] S1, presetting the output voltage, current, charging current limiting condition and charging cutoff condition of the charging device;

[0008] S2, connecting the charging device and the battery pack, and collecting and reporting the maximum voltage V max of each battery cell by the BMS (A) in the battery pack in real time;

[0009] S3, judging whether the charging current limiting condition and the charging cutoff condition are met in real time by the charging device, reducing the current output when the current limiting condition is met, and stopping the output when the cutoff condition is met, at this time, the battery pack is in a full charge / full capacity state;

[0010] ​S4 circumscribes BMS (B) and monitors V max when V max reaches the charging cut-off voltage V cut-off , sends a calibration SOC=100% command to BMS (A);

[0011] S5 BMS (A) receives the command in step S4, updates the SOC to 100% and saves it.

[0012] In step S2, the output of the charging device is connected to the discharge port of the battery pack, and the communication interface of the charging device is connected to the internal network CAN bus of BMS (A).

[0013] In the battery pack, the rated voltage of the single battery cell is 3.22V, a plurality of battery cells are combined in series and parallel to form a battery pack, and the total voltage of the battery pack is 3.22*S, and the rated capacity is 302*P, wherein S is the number of series battery cells in the battery pack, and P is the number of parallel modules in the battery pack.

[0014] In step S1, the charging cut-off voltage is 3.6V, and the charging cut-off condition is V max ≥3.6V.

[0015] The charging device includes constant current charging and constant voltage charging modes, the output voltage of the constant current charging is 90V, and the output current is 200A, and the current of the constant voltage charging is 30A.

[0016] When V maxx < 3.55V, the charging device is constant current charging;

[0017] When V maxx ≥3.55V, the charging device is converted to constant voltage charging.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] The scheme of charging the battery pack through the discharge port without protocol is realized, and the calibration SOC command is automatically sent when the battery pack is fully charged by using the external calibration device, thereby solving the SOC calibration problem after the battery pack is charged through the discharge circuit.

[0020] For battery packs with different internal structures or different charging protocols, the charging device and the external calibration device do not need to be changed, which not only eliminates the dependence on the charger, but also solves the efficiency problem of charging and capacity calibration of batch battery packs, and has high efficiency.

[0021] Constant current mode and constant voltage current limiting mode are set, and the output current is adjusted according to the battery cell parameters, so that the protocol-free charging is more secure.

[0022] BMS(A) real-time acquisition monomer cell maximum voltage and report to CAN bus, BMS(B) and charging equipment real-time access to the value and logical judgment, once triggered cutoff condition then take appropriate action, the realization of intelligent charging and automatic calibration, increase the intelligence of the whole system. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Comparison chart of traditional charging gun charging and the charging method of the application;

[0024] Figure 2 Electrical schematic diagram of charge-discharge different port battery pack;

[0025] Figure 3 For Figure 2 BMS and debugging port enlargement;

[0026] Figure 4 Battery pack discharge loop charging calibration principle diagram. DETAILED DESCRIPTION

[0027] The application will be further described below with reference to the drawings.

[0028] As Figures 2-4 shown, a method for charging battery pack through discharge port and automatically calibrating battery pack SOC, comprising the following steps:

[0029] S1 preset the output voltage, current and charging current limit condition and charging cutoff condition of the charging equipment, wherein the charging current limit voltage is 3.55V, the charging cutoff voltage is 3.6V, the charging current limit condition is V max ≥3.55V, and the charging cutoff condition is V max ≥3.6V.

[0030] S2 connect the charging equipment and the battery pack, the output of the charging equipment is connected to the discharge port of the battery pack, and the communication interface of the charging equipment is connected to the internal network CAN bus of BMS(A). The BMS(A) inside the battery pack collects and reports the maximum voltage V max of the monomer cell in real time. In the battery pack, the rated voltage of the monomer cell is 3.22V, a plurality of cells are combined in series and parallel to form a battery pack, the total voltage of the battery pack is 3.22*S, and the rated capacity is 302*P, wherein S is the number of series cells in the battery pack, and P is the number of parallel modules in the battery pack.

[0031] And, when the charging equipment is charging, including constant current charging and constant voltage charging two modes, the output voltage of constant current charging is 90V, and the output current is 200A, the current of constant voltage charging is 30A.

[0032] When V maxx <3.55V, the charging equipment is constant current charging at this time;

[0033] When V maxx ≥ 3.55V, at which time the charging device is converted to constant voltage charging.

[0034] S3 The charging device determines in real time whether the charging current limiting condition and the charging termination condition are met, when the current limiting condition is met, the charging device reduces the output current, when the termination condition is met, the output is stopped, at this time the battery pack is full / fully charged state.

[0035] S4 The external BMS (B) is connected, and the V max , when the V max reaches the charging cutoff voltage V cut-off , a calibrated SOC=100% instruction is sent to the BMS (A);

[0036] S5 After receiving the instruction in step S4, the BMS (A) updates the SOC to 100% and saves it in the internal FLASH.

[0037] In combination Figure 2 and Figure 3 , the electrical schematic diagram of the application, specifically including an all-in-one BMS (A), which is a commercial vehicle BMS "PWMBMS03" produced by Dongguan Qiwai Power Co., Ltd. The battery module is provided with a debugging port, a switch power-on port, a discharge port and a charging port, and is internally provided with a BMS (A) and a battery pack B1. The positive electrode of the battery pack B1 is connected in series with a fuse F1 and connected to the BMS power supply positive pin of the BMS (A), and the negative electrode is connected in series with a shunt FQ1 and connected to the BMS power supply negative pin of the BMS (A). The detection positive and negative pins of the shunt FQ1 are connected to the shunt 1 detection positive / negative pins of the BMS (A) respectively. The battery pack B1 is provided with a collection circuit in parallel, and the collection pins are connected to the positive and negative electrodes of B1 respectively. The collection circuit is connected to the module voltage collection pin of the BMS (A).

[0038] The BMS (A) is provided with a KeyOn pin connected to the starting switch K5 in the switch power-on port, and the other pin of the starting switch K5 is connected to one end of the discharge relay K1 and one end of the charging relay K2, and the two are connected to the BMS power supply positive pin. The other end of K1 is connected to the discharge + pin in the discharge port, and the other end of K2 is connected to the charge + pin in the charging port. A pre-charge circuit is provided in parallel on the discharge relay K1, including a pre-charge resistor R1 and a pre-charge relay K3. The charge - pin and the discharge - pin in the charging port and the discharge port are connected to the BMS power supply negative pin.

[0039] The A+ / A- pins are also arranged in the charging port and are connected to the A+ / A- pins in the BMS (A). The CAN2H pin in the charging port is connected to the charging CAN2H pin in the BMS (A) together with the charging debugging CANL pin, and the CAN2L pin is connected to the charging CAN2L pin together with the charging debugging CANH pin. The 485A debugging pin, the 485B debugging pin, the debugging CANH pin and the debugging CANL pin are also arranged in the debugging port and are connected to the corresponding pins in the BMS (A).

[0040] Specifically, the charging device is first set with parameters. Taking a lithium iron phosphate battery as an example, the single cell rated voltage is 3.22V, the charging cutoff voltage is 3.6V, and the rated capacity is 302Ah. A plurality of lithium iron phosphate cells are connected in series and parallel to form a battery pack. Taking a 1P25S module as an example, the rated total voltage is increased to 3.22*S=80.5(V) due to series connection, and the rated capacity is 302*P=302(Ah), wherein S is the number of series-connected cells in the battery pack, and P is the number of parallel-connected modules in the battery pack. For a battery pack with internal series and parallel connection structure, the maximum single cell voltage monitored by the BMS is generally used as a criterion, and charging is stopped when the voltage reaches the charging cutoff voltage. At this time, the cell has been fully charged, and if the charging continues, the battery will enter an overcharged state. Therefore, the condition for setting the output of the charging device to stop is set as Vmax≥3.6V.

[0041] Due to the charge and discharge characteristics of lithium batteries, generally constant current is used first, and relatively large current can be used for charging, so that the charging efficiency is relatively high. Therefore, during the constant current stage in the middle of the charging, the output voltage of the charging device is set to 90V, and the output current is set to 200A. The end of the charging is because the virtual voltage is relatively high due to the polarization resistance of the battery, and the constant voltage mode is used to reduce the charging current, so that the battery can be fully charged. Therefore, when Vmax≥3.55V, the output current of the charging device is set to 0.1C=30A.

[0042] The BMS (A) transmits the highest voltage of the single cell collected in real time to the internal network CAN bus. As the charging proceeds, when the highest voltage Vmax of the single cell reaches 3.55V, the charging device obtains this information and immediately adjusts the output current to 30A. During this stage from constant current to constant voltage and current limiting, the BMS (B) does not take any action.

[0043] The charging device continues to charge the battery pack, when the BMS(A) monitors that Vmax reaches 3.6V, the charging device and BMS(B) on the bus receive this information at the same time, then the charging device reaches the preset charging cutoff condition and stops output, BMS(B) sends the instruction of calibrated SOC=100% to the bus, BMS(A) receives the instruction and updates the SOC to 100% and saves it to the internal FLASH. The above completes a complete battery pack factory full charge and SOC calibration.

[0044] For the next calibration, only need to replace the battery pack that has completed the charge calibration with a new battery pack, after simple wiring, it can be used, which saves the step of replacing the charger due to different charging protocols, and multiple charging devices can run in parallel, greatly improving the production efficiency.

[0045] And instead of using plug-in charging, it uses a protocol-free charging method through the discharge port to charge the batch battery pack, and automatically calibrates the SOC of the battery pack when fully charged through the external calibration device, solving the charging and capacity calibration of the batch battery pack at the factory.

[0046] It realizes the protocol-free charging of the battery pack through the discharge port, and uses the external calibration device to automatically send the calibration SOC command when fully charged, solving the SOC calibration problem after charging the battery pack through the discharge circuit.

[0047] For battery packs with different internal structures or different charging protocols, there is no need to make any changes to the charging device and external calibration device, not only freeing from the dependence on the charger, but also solving the efficiency problem of charging and capacity calibration of batch battery packs at the factory, with high efficiency.

[0048] Two modes of constant current mode and constant voltage limited current mode are set, and the output current is adjusted according to the parameters of the battery cell, making the protocol-free charging more secure.

[0049] BMS(A) real-time collects the highest voltage of the single battery cell and reports it to the CAN bus, BMS(B) and the charging device real-time get the value and make logical judgment, once the cutoff condition is triggered, the corresponding action is taken, realizing intelligent charging and automatic calibration, and increasing the intelligence of the whole system.

Claims

1. A method of charging and automatically calibrating the SOC of a battery pack through a discharge port, characterized by, The method comprises the following steps: S1 presetting output voltage, current, charging current limiting condition and charging cutoff condition of the charging device; S2 connects the charging device and the battery pack, and the BMS (A) inside the battery pack collects and reports the highest voltage V of the single cell in real time max ; S3 real-time judging whether the charging current limiting condition and the charging cutoff condition are met by the charging device, when the current limiting condition is met, the charging device reduces the current output, when the cutoff condition is met, the output is stopped, at this time, the battery pack is in full charge / full power state; S4 circumscribes BMS(B), and monitors V max , when monitoring V max reaches the charging cut-off voltage V cut-off , sends a calibration SOC=100% instruction to BMS(A); S5 after receiving the instruction in step S4, the BMS(A) updates the SOC to 100% and saves it; In step S2 and step S4, the output of the charging device is connected to the discharge port of the battery pack, and the communication interface of the charging device and the external BMS(B) is connected to the internal network CAN bus of the BMS(A).

2. The method of charging and automatically calibrating the SOC of a battery pack through a discharge port according to claim 1, wherein, In the battery pack, the rated voltage of the single battery cell is 3.22V, a plurality of battery cells are combined in series and parallel to form the battery pack, the total voltage of the battery pack is 3.22*S, and the rated capacity is 302*P, wherein S is the number of series battery cells in the battery pack, and P is the number of parallel modules in the battery pack.

3. The method of charging and automatically calibrating the SOC of a battery pack through a discharge port of claim 1, wherein, In step S1, the charge cut-off voltage is 3.6 V, and the charge cut-off condition is V max ≥ 3.6 V.

4. The method of charging and automatically calibrating the SOC of a battery pack through a discharge port of claim 1, wherein, The charging device includes constant current charging and constant voltage charging modes, the output voltage of the constant current charging is 90V, the output current is 200A, and the current of the constant voltage charging is 30A.

5. The method for charging and automatically calibrating the SOC of the battery pack through the discharge port according to claim 4, characterized in that, When V max <3.55V, at which time the charging device is constant current charging; When V max ≥ 3.55V, at which time the charging device transitions to constant voltage charging.

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