What is a Battery Protection IC?

Lithium-ion batteries typically consist of cells, battery protection boards, and casings, with the protection board including the battery protection IC. During normal operation, lithium-ion batteries undergo a chemical reaction that stops the conversion of electrical energy to chemical energy. However, under certain conditions, such as overcharging, overdischarging, and overcurrent, the battery may experience chemical side reactions. These reactions can severely impact the battery's performance and lifespan, potentially causing a buildup of gases that increase internal pressure, leading to explosions and safety issues. Therefore, all lithium-ion batteries require a protection circuit, which is the battery protection IC, to effectively monitor the charging and discharging states and to interrupt the charging and discharging circuits under certain conditions to prevent damage to the battery.

Battery Protection IC Circuit Diagram Example:

Common Battery Protection IC

TI Series: BQ29700 (Single Cell), BQ294707 (2/4 Cells), BQ771809 (2/5 Cells)

2. Seiko (Japan) Series: S8261x (Single Section), S8232X (Double Section)

Ricoh (Japan) Series: R5400, R5402, R5421, R5426 (Single Battery)

4. Beauty of Japan Series: MM3077 (Single Section), MM1414 (3/4 Section)

5. Fuchin (Taiwan) Series: DW01+, DW01-, FS312F, FS326 Series (Single Section), FS3332 (Double Section)

6. New Tai Chi Series: CS213 (Single Section)

7. Star River (Beijing) Series: VM7021 (Single Cell)

8. Slan (Hangzhou) Series: SC451 (Single Section)

Li-ion Battery Protection IC Operation Method

AutoRelease (Self-Recovery) Version

Overcharge Protection: As the charger charges the battery, the battery voltage gradually increases. Upon reaching Vdet1, the protection IC activates, causing Cout's level to switch from high to low, thereby preventing the charger from continuing to charge the cell, achieving the protective effect.

Method 1: The charger will cease charging the battery again when the cell voltage drops below Vrel1 while the charger is continuously connected.

Method 2: The device will continue charging as long as the charger is reconnected (disconnecting the charger will deactivate the overcharge protection).

Note: Upon connecting the charger, if any of the above conditions are met, the Cout level will shift from low to high, thereby deactivating the protection.

Over-discharge Protection: When the battery discharges through the load, the cell voltage will continue to drop below Vdet2. At this point, the protection IC will cease its protective action, and the Dout pin will switch from high to low level, thereby shutting off the Mosfet to prevent the cell from continuing to discharge to the load.

Method 1: Under the condition of plugging in the charger, the voltage only needs to exceed Vdet2 to release the protection. Method 2: Under the condition of not plugging in the charger, the battery voltage must exceed Vrel2 to release the protection. When the charger is connected or the battery voltage exceeds Vrel2, Dout will switch from low to high, allowing the Mosfet to conduct and continue discharging the battery to the load.