Lithium battery BMS with high number of strings

How to choose a BMS for lithium batteries?

To build safe-high performance battery packs, you need to know how to choose a BMS for lithium batteries. The primary job of a BMS is to prevent overloading the battery cells. To be effective, the maximum rating on the BMS should be greater than the maximum amperage rating of the battery.

What does a BMS prevent in lithium-ion batteries?

A BMS prevents your battery cells from being drained or charged too much. Another important role of the BMS is to provide overcurrent protection to prevent fires. Lithium-ion batteries do not require a BMS to operate, but a lithium-ion battery pack should never be used without a BMS.

Can a lithium ion battery pack have multiple strings?

Whenever possible, using a single string of lithium cells is usually the preferred configuration for a lithium ion battery pack as it is the lowest cost and simplest. However, sometimes it may be necessary to use multiple strings of cells. Here are a few reasons that parallel strings may be necessary:

How does a battery management system (BMS) work?

A battery management system (BMS) monitors the cell voltage of each cell group. If any of them go lower than a certain threshold (usually around 2.6 volts), the BMS disconnects the cells to prevent damage. During charging, a high voltage is applied across many sets of lithium-ion cells in series.

How many cells can be used in a BMS?

Even though 8 cells are used, because each cell is paralleled with one other cell, the BMS can treat each pair of cells as a single cell. This allows the designer to use a smaller BMS. The above configuration is a “4S2P” configuration.

Why do we connect multiple lithium batteries to a string of batteries?

Connecting multiple lithium batteries allows us to build a battery bank with the potential to operate at an increased voltage, or with increased capacity and runtime, or both.