Why your battery need a BMS?

Why your battery need a BMS?

By Sixpack | June 13th 2022

A BMS lithium-ion battery intelligent management system monitors the voltage of individual battery packs and tests low performance cells before they are packaged.

Davies. Bennington

Sr. Project Manager

8 min read

A BMS lithium-ion battery intelligent management system monitors the voltage of individual battery packs and tests low performance cells before they are packaged. This 100% testing ensures higher yields, higher battery capacity and eases warranty commitments. A good BMS can also test for moisture in Li-ion battery packs to avoid accidents.

1.Why do lithium batteries need a battery management system(BMS)?

Lithium-ion batteries are at risk of explosion when severely overcharged, causing damage to the lithium-ion battery pack and posing a threat to the user’s life. Therefore, it is necessary to equip lithium-ion battery packs with a targeted lithium-ion battery management system BMS for effective monitoring, protection, energy balancing and fault alarm to improve the overall efficiency and service life of lithium-ion batteries.

(1) Safety

The safety of lithium-ion batteries is poor, and defects such as explosions occur from time to time. In particular, lithium-ion batteries with lithium cobaltate as the cathode material cannot be discharged at high currents and have poor safety. In addition, almost all types of lithium-ion batteries overcharge or overdischarge will cause irreversible damage to the battery. Lithium-ion batteries are also extremely sensitive to temperature: if used under high temperature conditions, it may cause electrolyte analysis, combustion or even explosion; low temperature will lead to significant deterioration of lithium-ion battery performance and affect the normal use of equipment.

Due to the limitations of the battery production process, the internal resistance and capacity of each battery cell will vary. When multiple battery cells are used in series, it will cause inconsistent charge and discharge rates of each cell, resulting in low utilization of battery capacity. In view of this, lithium-ion batteries usually require a dedicated protection system to monitor the health status of the battery during actual use, thus managing the process of using lithium-ion batteries.

(2) Maintainability

The capacity decay and power of lithium-ion batteries at low temperatures cannot be accurately predicted, making the equipment less maintainable. Long-term online instruments require regular battery replacement, while remote monitoring equipment works in scattered locations with long distances between sites, making battery replacement workload and cost high.

In order to reduce maintenance workload and maintenance costs, the lithium-ion battery BMS management system needs to have an accurate charge status estimation function to accurately grasp the battery’s charge status and replace the battery more purposefully; at the same time, the battery management system needs to have low power consumption to reduce maintenance frequency and extend the battery’s service life. Therefore, for long time continuous power supply remote monitoring instruments, reasonable design of lithium-ion battery BMS management system for the maintenance of equipment has a very important significance.

2.The role of BMS lithium-ion battery management system.

Battery Management System (BMS) is a set of control systems to protect the safety of the use of batteries, always monitor the use of battery status, through the necessary measures to regulate the abnormal use of battery status, for the replacement cabinet and the use of the vehicle safety to provide security. the main purpose of the BMS lithium-ion battery management system is to ensure the design performance of the battery system, from security, durability, power to provide the role of three aspects.

(1) Security, BMS lithium-ion battery management system can protect the battery monomer from damage, to guard against security incidents.

(2) Durability, BMS lithium-ion battery management system can make the battery work in a reliable and safe area, to extend the service life of the battery.

(3) Power aspect, the lithium-ion battery to maintain the working condition to meet the requirements of the vehicle.

3. Core functions of Li-ion battery BMS

(1) Single cell voltage acquisition;

(2) Single cell temperature acquisition;

(3) Battery pack current testing.

Accurate measurement of temperature is also quite critical for the working state of Li-ion battery pack, including individual cell temperature measurement and pack heat dissipation liquid temperature monitoring. This requires a reasonable setting of the location and number of temperature sensors used to form a good match with the BMS control module.

● SOC technology: Simply put, it is how much charge is left in the battery

SOC is the most important parameter in BMS, because everything else is based on SOC, so its accuracy and robustness (also called error correction capability) are extremely important. Without accurate SOC, no amount of protection functions can make the BMS work properly, because the battery will often be in a protected state, not to mention extending the life of the Li-ion battery.

● Equalization Technology

Passive equalization generally uses the resistive heat release method to release the “extra power” of high capacity batteries to achieve the purpose of equalization, the circuit is simple and reliable, the cost is lower, but the battery efficiency is also lower.

This is an explanation of the lithium-ion battery BMS management system. Today’s demanding power use (such as energy storage, automotive and electric vehicles) using increasingly complex design of lithium batteries (LIB), must be through the battery management system (BMS) to ensure optimal efficiency and safety.

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