What is the battery protection board management system BMS?
The composition of the finished lithium battery has two main parts, the battery cell and the battery protection board BMS.
The battery pack protection board usually includes control IC, MOS switch, resistor, capacitor and auxiliary device NTC, ID memory and so on. 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, thereby prolonging the battery life.
The working principle of the protection board
The protection function of the lithium battery pack is usually completed by the protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage of the battery cell and the charging and discharging circuit under the environment of -40℃ to +85℃. It can control the on and off of the current loop in time; PTC prevents severe damage to the battery under high temperature environment.
How to choose a protection board
1. After clarifying your battery cell materials (ternary, iron-lithium, titanium-lithium), determine the number of strings (connected) or parallel (connected) of the battery cells, and choose according to the number of strings.
2. Determine whether the battery pack is charged at the same port or separate port; the same port is the same line for charging and discharging, and the separate port is independent of the charging line and the discharging line.
3. Determine the current value required by the protection board: I=P/U, that is, current=power/voltage. Remember, this is only a theoretical value. In reality, we use this theoretical value as a reference. Taking into account the load and the uphill and just-starting environment, generally two-wheel electric vehicles choose more than 2 times this theoretical value, and three-wheel electric vehicles choose more than 3 times this theoretical value. A four-wheel low-speed car generally has about 3.5 times. Inverter and energy storage together, 1.2 times is about the same. Or refer to the current limit of the controller of the electric vehicle, the current value of the protection board must be greater than the current limit value of the controller
4. Equalization means that when the voltages of the batteries in each string of the battery pack are not much different, the voltages of the batteries in each string tend to be consistent through the equalization resistance discharge. Divided into active equilibrium and passive equilibrium.
5. Temperature control protection, which protects the battery pack by testing the temperature of the battery.