A battery management system (BMS) is an electronic system that controls the charging and discharging of a rechargeable battery (cell or battery pack) by protecting the battery from operating outside its safe operating area monitoring its state, calculating secondary data, reporting that data, controlling its environment, and balancing it.
Basic Features of BMS:
Overcharge Protection: Protects the cells as well as the battery from overcharding beyond its safe limit.
Deep Discharge Protection: Protects the cells as well as the battery from deep discharding while powering a load.
Cell Balancing: When a cell is fully charged bypass that cell to let the other cells to be charged.
Types of BMS depend upon the type of cells as well as the number of cells in series. As per the number of cells in series, BMS is classified as
1S: Only one cell
2S: 2 number cells in series
3S: 3 number cells in series
and so on...
The voltage of BMS depends upon the cell type like for Li-Ion 1S BMS its rated voltage is 3.7V. For 2S it would be 7.4V. On the other hand for lithium ferro-phosphate cell (LiFePO4), 1S BMS would be 3.2V and 2S would be 6.4V, and so on...
Every BMS has it's terminal marked connection needs to be done as per marking.
B- Terminal is for Battery Negative
B+ Terminal is for Battery Positive
P+ is for Power Positive
P- is for Power Negative
This lithium ferro-phosphate 2S BMS has five terminals apart from B+, B-, P+, P- it has one extra terminal that is BM. This BM terminal goes to the middle terminal of the battery series.
The Li-Ion 2S BMS also has the same pin configuration.
For 3S Li-Ion BMS, the Connection diagram is shown above. The lithium ferro-phosphate does not come with a 3S configuration.
Instead lithium ferro-phosphate BMS comes with 4S configuration. The connection diagram is shown.
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