In practical application, according to the requirements of a brand of electric bicycle factory, the design and implementation of two groups of 36V8A.h lithium manganate power lithium battery pack protection plate, 10 series, parallel, 36V8A.H. The single lithium ion battery protection chip adopts the S28241 of Japan Seiko Company. The protection board is mainly composed of the main circuit, the control circuit, the shunt discharge branch, the filter, the optical coupling isolation and the level conditioning circuit. The discharge branch current is about 800mA, and 510 resistors are used to form a resistance network.

The debugging work is divided into two parts: voltage test and current test. Voltage test includes charging performance detection overvoltage, equalized charging and discharge performance detection undervoltage two steps. The battery analog power supply can be used instead of the actual battery pack for testing. Because of the series of multiple batteries, the test cost of this method is high. You can also use the assembled battery pack to directly test, cycle charge and discharge of the battery pack, observe whether the protection device is normal operation under overvoltage and undervoltage, record the real-time voltage of each battery under overcharge protection, and judge the performance of balanced charging. However, this method takes a long time to test once. When the battery pack is tested for charging performance, the 3-bit semi-precision voltmeter is used to monitor the charging voltage of 10 batteries. It can be seen that each battery is within the normal working voltage range, and the difference between the monomers is very small. The voltage deviation in the charging process is less than 100mV, the full charging voltage is 4.2V, and the voltage deviation is less than 50mV. The current test part includes two steps: overcurrent detection and short circuit detection. Over current detection can be in the resistance load and power loop between a series of ammeter, slowly reduce the load, when the current increases to the over current value, to see whether the ammeter indicates disconnection. Short circuit detection can directly short-circuit the positive and negative electrodes of the battery pack to observe the ammeter status. Under the premise that the device is in good condition and the circuit is welded correctly, the current can also be directly tested by the status of the power indicator on the protection board.

In practical use, considering the external interference may cause the battery voltage is not stable, it will cause voltage extremely short time over-voltage or under-voltage, leading to misjudgment battery protection circuit, so the protection chip with a corresponding delay logic, when necessary, can add the delay circuit on the protection board, this will effectively reduce the external interference caused by the possibility of a protection circuit misoperation. When the battery pack is not working, the switching devices on the protection board are disconnected, so the static loss is almost 0. When the system is working, the important loss is the on-state loss on the two MOS tubes in the main circuit. When the equalization circuit is working in the charging state, the thermal loss of the resistance in the shunt branch is large, but the time is short, and the overall dynamic loss is at an acceptable level in the normal working cycle of the battery pack.