Why do lithium batteries need to add a protection board?

2021-08-13 10:34:37 0

Why do lithium batteries need to add a protection board, the principle of lithium battery protection board. The lithium battery protection board, as the name suggests, is used to protect the lithium battery. The function of the lithium battery protection board is to protect the battery from over-discharge, over-charge, over-current, and output short-circuit protection. The lithium battery plus the protection board is determined by the characteristics of the lithium battery. Lithium batteries have its safe discharge and charge and overcurrent limits, and the protection board is added to keep these values within the safe range when using lithium batteries. Usually, after the lithium battery is added with a protection board, the voltage of the battery will be controlled within this voltage, which plays a role in protecting the lithium battery.

Why do lithium batteries need to add a protection board?

Because the lithium battery is overcharged, over-discharged, or short-circuited, it is possible that the battery will be scrapped. The protection board is used for this protection. If you can ensure that the battery is overcharged, over-discharged, or short-circuited during use, you don’t need the protection board. . During the use of lithium batteries, every time they are overcharged, over-discharged, or short-circuited, the battery life will be reduced. In severe cases, the battery will be scrapped directly! If there is no lithium battery protection board, directly short-circuit the lithium battery and overcharge it will cause the battery to bulge. In severe cases, it will leak, depressurize, explode or catch fire.

The protection board is to ensure safety and the lithium battery is not considered to be overcharged and overdischarged, because the previous lithium-ion battery overcharge and overdischarge will cause the battery damage or explosion, fire and other dangers, so when the lithium-ion battery is introduced The protection board has also emerged. Recently, with the emergence of lithium iron phosphate batteries, it is said that lithium iron phosphate batteries are not afraid of overcharging or overdischarging. Therefore, there has been a theory that it can be done without a protection board, but so far There is no battery manufacturer that publicly declares that it does not use the protection circuit. The protection board is the bodyguard, and the protection board is to ensure the safety of the lithium battery.

Of course, if the design of the lithium battery protection board is not good, it will damage the battery, but the role of the protection board is to protect the battery and prevent the battery from coming out of safety. Consider not using the protective board when putting it!

The function of the lithium battery protection board is mainly to protect the cells of the rechargeable battery, maintain the safety and stability of the battery during the charging and discharging process, and play an important role in the performance of the entire battery circuit system.

1. Overcharge protection function: The overcharge protection function means that when a certain voltage (hereinafter referred to as overcharge detection voltage) is reached, it is forbidden to continue charging by the charger. That is, the MOS tube that controls overcharge is turned off to stop charging.

2. Over-discharge protection function: The over-discharge protection function stops discharging the load when the voltage of the lithium battery becomes low. The MOS tube that controls the over-discharge enters the off state, and it is prohibited from discharging. This process is just the opposite of the action during overcharge detection.

3. Over-current protection function: The over-current protection function stops discharging the load when a large current is consumed. The purpose of this function is to protect the battery and the MOS tube to ensure the safety of the lithium battery under working conditions. After the over-current detection, the battery will return to the normal state after being separated from the load, and can be recharged or discharged.

4. Short circuit protection function: In addition to the control IC, there is an important component in the circuit, which is the MOSFET, which acts as a switch in the circuit. Because it is directly connected in series between the battery and the external load, it is turned on. Impedance has an impact on the performance of the battery. When the selected MOSFET is better, its on-resistance is very small, the internal resistance of the battery pack is small, the load capacity is also strong, and it consumes less electric energy during discharge. When your battery is accidentally short-circuited, the protection board will automatically turn off within a few milliseconds and will not be powered on. At this time, it will be fine if the positive and negative poles touch one.

The lithium battery protection board is a protection for the charging and discharging of the series lithium battery pack; when fully charged, it can ensure that the voltage difference between the individual cells is less than the set value (generally ±20mV), and realize the equal charge of the individual cells of the battery pack , Which effectively improves the charging effect in the series charging mode; at the same time, it detects the overvoltage, undervoltage, overcurrent, short circuit, and overtemperature status of each single cell in the battery pack to protect and extend the battery life; undervoltage protection makes every A single-cell battery is used to prevent damage to the battery due to over-discharge.