All portable electric devices, from cell phones to electric cars, require a battery. For economy, rechargeable batteries are better. In simple applications these can be used as dumb power sources but when performance is an issue a "smart battery" (a battery with a management system) is preferred.

A battery management system monitors the state of a battery and has control over charging and discharging. The purpose of the device is threefold:

  1. Reduce the risk of damage to the battery.
  2. Make the most efficient use of the available energy
  3. Provide information about the battery state

A battery will last longer if used properly. The BMS should prevent overcharging, overly deep discharge, excessive current draws and high temperature situations. This is especially important with Lithium Ion batteries where misuse can end in thermal runaway, explosion and fire.

Some BMS include a DC/DC converter output to the load. This enables the system to supply the correct minimum voltage required, instead of wasting energy over the whole voltage discharge curve.

A BMS will try to track its battery's State of Charge (how "full" the battery is). This is required to control the charge/discharge process, and is also useful information to pass onto other systems or the user in the form of a remaining energy indicator. A sophisticated BMS will track the degradation of the battery over its lifetime.

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