Lithium battery protection boards are often involved when lithium batteries are connected in series and parallel to form a battery pack. So what is a lithium battery protection board? What are the functions of the protection board?

What is a lithium battery protection board?

Lithium battery protection board is a circuit board that plays a protective role. It is mainly composed of electronic circuits. It accurately monitors the voltage of the cell and the current of the charging and discharging circuit under the environment of -40°C to +85°C, and controls the on and off of the current circuit in time.

Ordinary lithium battery protection boards usually include control ICs, MOS switches, resistors, capacitors and some auxiliary devices. The control IC controls the MOS switch under all normal conditions to make the cell and the external circuit conduct, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the safety of the cell.

What are the functions of the lithium battery protection board?

The lithium battery protection board can play a role in the charge and discharge protection of the series and parallel battery packs, and can detect the overvoltage, overcurrent, overtemperature, undervoltage, and short circuit status of each single cell in the battery pack, prolonging the battery life and avoiding The battery is damaged by over-discharge. Lithium battery protection board is an indispensable part of lithium battery.

The lithium battery protection board also has a balanced protection function, and there are two ways of energy consumption and energy transfer. Energy-consumption equalization refers to the use of resistors to consume a certain battery with high power or voltage among multiple strings of batteries. Energy-consuming balance is divided into equalization during charging, voltage fixed-point equalization, and static automatic equalization.

Balance while charging: When charging, when the voltage of any battery is higher than the average voltage, the protection board will start the balance protection.

Voltage fixed-point equalization: The lithium battery protection board is set to start the equalization at a voltage point, which is only performed at the end of the battery charging, and the equalization time is short.

Static automatic balance: During the process of charging or discharging, even if the battery is in a static state, when the voltage is inconsistent, the lithium battery protection board will start the balance protection until the voltage remains consistent.

The transfer type is to transfer a large-capacity battery to a small-capacity battery by means of energy storage, and to check the capacity of the battery for balance, which is divided into capacity constant balance and capacity fixed-point balance.

Why do some batteries need a protection board, and some do not need it?

Adding a protective plate to the battery is for user safety. Lithium battery has its safe discharge charge and overcurrent limit. The protection board is added so that these values do not exceed the safety range when using lithium batteries.

For example, the upper limit of the safety voltage of a lithium battery is 4.25V. If the board is not added, it will continue to be charged when using a charger without overcharge protection. It's like a person who is full, and you tell him to continue to eat, and in the end it will die, and the lithium battery will also die. The role of the protection board is to stop charging when he is full.

The principle of discharge and overcurrent detection is also the same. Therefore, the battery with the protection board can control the lithium battery to work in the specified working environment. The charging protection voltage is generally 4.25V protection, and the discharge protection is generally 2.75V protection. The charging current can be within the maximum tolerance range of the lithium battery, and the safety is greatly improved.

Putting a protective board on the battery will also limit the output current. Generally speaking, there are chips on the protection board, about 2A for a single chip, and about 4A for a dual chip.

Many high-power devices in life, such as e-cigarettes, model airplanes, and electric vehicles, require high-current power supply. Because they are easily used violently (referring to excessive charging and discharging), the battery life is relatively low; at the same time, the battery is small in size, and the conventional high-power protection board The volume is too large; the price of the protection board with ultra-low internal resistance is very expensive. In order to reduce the discharge loss and improve the cost performance, the protection board is generally not added, and the battery protection function is selected on the power receiving device.

What is the difference between lithium battery protection board and BMS (Battery Management System)?

Both the lithium battery protection board and the battery management system protect the lithium battery. The difference between them is:

1. The lithium battery protection board is composed of IC, MOS tube, resistor and capacitor components, and is an important component of lithium battery. The battery management system can be edited and comes with battery management software, which is relatively smarter, equivalent to the brain of a lithium battery, and plays a role of control.

2. The lithium battery protection board plays an important role in the 3C lithium battery and power battery fields, and the battery management system is applied in the power battery field.

3. The battery management system operates better than the battery protection board, but its performance in low temperatures is unstable.