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Why PCB/ BMS is required in lithium battery pack?


With the advantages of high energy density, light weight, long life cycle, the market of lithium-ion battery is growing because they can be used in various applications as a kind of new energy battery. It ranges from electronic devices like laptops to golf carts, scooter, etc. and also become popular in solar power system, communication base station and other fields.

A lithium battery is composed of: the anode and the cathode; a separator between the two electrodes; and an electrolyte that fills the remaining space of the battery. Due to the special material of lithium battery, it needs protection to prevent from damage. So how to ensure the lithium batteries work well? This is where the protection circuit board comes into play.


What is lithium battery protection circuit board?


Protection circuit board (PCB), also called protection circuit module (PCM) is the "heart" of Lithium battery pack. It plays a crucial role in the normal use of lithium battery. It is used to protect Lithium battery pack from being overcharged, over-discharged and over-drain, therefore it is the must to have to avoid Lithium battery pack from explosion, fire and damage. For low voltage lithium battery packs (<20 cells), you shall choose PCM with equilibrium function to keep each cell in balance and good service life. For high voltage Lithium battery pack (>20 cells), you shall consider advanced BMS ( battery manage system) to monitor each cell's performance to ensure battery's safer operation.

What is the functions of Protection Circuit Board?

The protection of lithium battery is usually completed by the coordination of protection circuit board and PTC. The protection circuit board can monitor the voltage of the battery cell and the current during the charging and discharging of the battery at the temperature from -40 to +85 accurately, and also control the on and off of the current circuit instantly. The PTC prevents severe battery damage at high temperature. Battery University points out that the resistance of the positive thermal coefficient (PTC) (blue) is low during normal operation and increases when the temperature rises above a critical level to reduce current flow. The PTC is reversible and returns to high conductivity when the temperature normalizes. 

Here are some important functions of protection circuit board: 

Overcharge Protection Function

When the charging voltage is 4.1 V or 4.2 V/cell, the lithium batteries can be safely charged, but no higher. If the battery is overcharging, it can cause damage to the battery and create a safety hazard, including fire danger. A battery protection circuit is used to monitor the voltage and prevent this so as to longer the battery life.


Over-discharge Protection Function

Lithium batteries are completely empty when discharged to 2.5 V/cell. Discharging a lithium cell nearly to dead has a stressful impact to the cell and reduces cell lifetime. A good battery protection circuit will also provide over-discharge protection.


Current Circuit  Control Function

Discharging too quickly will do harm to lithium batteries. Lithium batteries have maximum discharge current ratings. A battery protection circuit will take the battery out of the circuit if the load current is too high.

A protection circuit board can ensure the safety and good performance of lithium battery. Similarly, a elaborate design of protection circuit board is of great importance to improve the safety of battery. While selecting lithium batteries for your product, take UFO lithium battery into consider. UFO Battery has its own BMS R&D Team and dedicated to manufacture high-quality lithium-ion battery for customers. 

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