The protection function of lithium ion battery BMS

Power lithium-ion battery management system can effectively monitor, protect, energy balance and fault alarm the Lithium Polymer Battery pack, thereby improving the working efficiency and service life of the entire power LiFePO4 Battery pack. Lithium-ion batteries are widely used in various precision devices due to their high working voltage, small size, light weight, high energy density, no memory effect, no pollution, low self-discharge, long cycle life and many other advantages.

When the smart battery is in the state of charging and discharging, if the detected current exceeds 3A and is still greater than 3A after a delay of 0.2s, it is judged to be overcurrent. At this point, the protection executive circuit disconnects the discharge protection switch. The condition for cancelling the protection is that the charger is connected. If a connected charger is detected, the overcurrent protection is cancelled, otherwise the smart battery is always protected.

BMS battery management system is mainly responsible for controlling battery charging and discharging, realizing battery status estimation and other functions, realizing battery status monitoring, battery status analysis, battery safety protection, energy control management, and battery information management.

Lithium Batteries have defects such as poor safety and explosion. In particular, lithium-ion batteries with lithium cobaltate as the positive electrode material can not be discharged with large current, and the safety is poor. In addition, almost all kinds of Lithium Iron Phosphate Battery overcharge or overdischarge can cause irreversible damage to the cell. Lithium-ion batteries are also extremely sensitive to temperature: if used at too high a temperature, it may cause decomposition, combustion or even explosion of the electrolyte; Too low temperature will cause the performance of the Lithium Battery to deteriorate significantly, affecting the normal use of the equipment.

When the battery voltage exceeds 4.2v or the total voltage exceeds 16.8v during the charging process, the battery is overcharged. At this point, the protection executive circuit cuts off the charge protection switch. In the overcharge release state, the voltage of each battery is less than 4V.

The battery management system (BMS) can collect, process and store important information in real time during the operation of the battery pack, exchange information with external devices such as controllers, and solve key issues such as safety, availability, ease of use and service life of the lithium-ion battery system. The main application is to improve the utilisation rate of the battery, prevent overcharging and over-discharging of the battery, extend the life of the battery and monitor the status of the battery. Generally speaking, it is a set of management, control, use of battery pack system.

The battery management system is closely integrated with the power lithium-ion battery of electric vehicles, real-time detection of battery voltage, current and temperature through sensors, leakage detection, thermal management, battery balance management, alarm reminder, calculation of remaining capacity (SOC), discharge power, and report the degree of battery deterioration (SOH) and remaining capacity (SOC) status. Also according to the battery voltage, current and temperature with the algorithm to control the maximum output power to obtain the maximum mileage, and the algorithm to control the charger for the best current charge, through the CAN bus interface with the vehicle controller, engine controller, energy control system, vehicle display system and other real-time communication.