Battery Management Systems are the brains behind battery packs. They manage the output, charging and discharging and provide notifications on the status of the battery pack. They also provide critical safeguards to protect the batteries from damage.
A battery management system is essentially the “brain” of a battery pack; it measures and reports crucial information for the operation of the battery and also also protects the battery from damage in a wide range of operating conditions.
Lithium ion battery cells have two critical design issues; if you overcharge them you can damage them and cause overheating and even explosion or flame so it's important to have a battery management system to provide overvoltage protection .
Lithium ion cells can also be damaged if they're discharged below a certain threshold, approximately 5 percent of total capacity. If the cells are discharged below this threshold their capacity can become permanently reduced.
To ensure a battery's charge doesn't go above or below its limits, a battery management system has a safeguard device called a dedicated Lithium-ion protector
The function of battery management system is energy management, a battery pack usually consists of several individual cells that work together in combination. Ideally, all the cells in a battery pack should be kept at the same state of charge. If the cells go out of balance, individual cells can get stressed and lead to premature charge termination and a reduction in the overall cycle life of the battery. The cell balancers of the battery management system, shown here, extend the life of the battery by preventing this imbalance of charge in individual cells from occurring.