To improve battery safety, battery monitoring and protection are important in a charger system. The main job of a charger is to charge the battery. The chargers are essentially power supplies with complex state machines and analog feedback loops. In general, chargers do not offer battery monitoring function and only implement basic battery protection functions such as under-voltage protection, over-voltage protection and over-current protection.

The gauges are micro-controllers using ADCs and digital logic. Although a few chargers offer battery monitoring as an extra feature in addition to regular charger, a gauge makes more accurate voltage, current and temperature measurements compared to that of a charger. For accurate ADC measurements and full-featured battery monitoring function, a gauge is recommended.