If lithium-ion battery packs do not have protection boards, the battery life will be greatly reduced for electric vehicle users who do not pay attention to daily battery protection, and more malfunctions will occur, leading to some dangerous situations.
During use, each instance of overcharging, over-discharging, or short-circuiting reduces the lifespan of a lithium-ion battery. In severe cases, the battery may become unusable. Generally, the overcharge voltage of a single lithium-ion battery should not exceed 4.25V, the over-discharge voltage should not exceed 2.75V, and the maximum charge/discharge current should be 1C (C represents the battery capacity; for example, if the battery is 1200mAh, a 1C charge/discharge current is 1.2A). Without a protection board, directly short-circuiting or overcharging a lithium-ion battery pack can cause the battery to swell, and in severe cases, it can lead to leakage, pressure loss, explosion, or fire.
Key functions of lithium-ion battery pack protection boards:
1) Overcharge protection function
Overcharge protection means that when a certain voltage (hereinafter referred to as the overcharge detection voltage) is reached, the charger will prevent further charging. That is, the MOSFET controlling overcharge will be turned off, stopping the charging process.
2) Over-discharge protection function
The over-discharge protection function stops discharging to the load when the battery voltage drops. It turns off the MOSFET controlling over-discharge, preventing it from discharging. This process is exactly the opposite of the overcharge detection mechanism.
3) Overcurrent protection function
The overcurrent protection function stops discharging to the load when a large current is consumed. This function aims to protect the lithium-ion battery pack and MOSFET, ensuring battery safety during operation. After overcurrent detection, the battery will return to normal operation once disconnected from the load and can be recharged or discharged.
4) Short circuit protection function
Should lithium-ion battery pack protection boards include an equalization function?
There are situations where a lithium-ion battery pack protection board needs to include balancing: When the battery pack has been stored for a long time after production, the voltage of each string of batteries in the entire battery pack will be inconsistent due to the different static power consumption of each circuit of the protection board and the different self-discharge rates of each cell. This results in a significant voltage difference. However, while ensuring the capacity is consistent, balancing can balance the voltage of the battery pack, thereby achieving the effect of full charging and full discharging of the battery pack and maximizing the efficiency of the battery pack.
Ineffective balancing: Many people believe that balancing is useful in the middle and later stages of lithium-ion battery pack use. However, in the middle and later stages of battery pack use, due to the different capacity loss of each cell, a capacity difference is caused. The balancing by the protection board cannot make up for the cell capacity difference. On the surface, the voltage of each string of the battery pack is the same, but due to the difference in capacity, during charging and discharging, the single cell with the lower capacity is often the first to be over-discharged and over-charged. Therefore, the capacity of the battery pack is reflected by the single cell with the lower capacity.
