Analysis of Protection Board for Lithium Battery Pack of Electric Bicycle

With the improvement of people’s living standards, electric bicycles have been widely used, and each electric bicycle has a unique lithium battery as its back storage power, and each battery contains an unknown lithium The battery protection board and the lithium battery protection board play the core protective role in the battery, and have the main protection functions of overcharge, overdischarge, and overcurrent for the battery. Lithium battery protection board is so important, it is very important to understand its common sense. Today, the Chinese Chuangfa will learn with everyone the knowledge of the analysis of electric bicycle lithium battery pack protection board.

1. Connect the lithium battery and the protection board according to the wiring diagram. The protection circuit detects the voltage and current of each battery in the series battery pack, and controls the charging and discharging process of the battery pack. The voltage of each battery in the battery pack is between the overcharge detection voltage and the overdischarge detection voltage, and when there is no short circuit in the output, the MOS tube is turned on, and P+ and P- can be used to discharge the battery pack;

2. Battery pack over-discharge protection function When the voltage of any battery in the series battery pack drops to the over-discharge detection voltage and reaches the over-discharge delay time, the over-discharge protection function is activated, cuts off the discharge MOS tube, and prohibits The battery pack outputs current to protect the safety of the battery pack. The circuit board enters the sleep state, and the current consumption of the circuit board is below the sleep current. The circuit that enters the sleep state can only be restored after the charger is connected and the battery voltage exceeds the over-discharge recovery voltage;

3. Battery pack overcharge protection function. During the process of charging the battery pack through P+ and C-, when the voltage of any battery rises to the battery overcharge detection voltage and exceeds the overcharge delay time, The overcharge protection function is activated, cut off the charge MOS tube, prohibit charging the battery pack, to protect the safety of the battery pack. When the battery pack is connected to the load to discharge or the battery voltage drops below the overcharge recovery voltage, the overcharge state is restored;

4. Battery pack short-circuit protection function. When the battery pack discharge port P+ and P- are short-circuited, the protection circuit will cut off the discharge MOS tube after the short-circuit protection delay time, and prohibit the battery pack from discharging externally. When the external short circuit is removed After removal, the circuit automatically recovers;

5. Battery pack overcurrent protection function When the battery pack discharge port P+ and P- have overcurrent phenomenon, the protection circuit will cut off after the overcurrent protection delay time The discharge MOS tube prohibits external discharge of the battery pack. When the external short circuit is removed, the circuit automatically recovers.

6. When the battery pack charge equalization function causes a difference in the battery voltage of each battery in the battery pack due to the matching of the battery or the influence of the external environment, if the battery voltage difference between the series connected groups exceeds the set value The equalization circuit is allowed to work, the equalization starts during the charging process, the equalization resistor discharges the battery pack with the highest relative capacity, and the equalization current is the equalization absorption current value to reduce the voltage rise of the battery pack. When the voltage difference between the battery packs in series is less than When setting the value, the equalization circuit is prohibited from working, and there is no equalization.