Battery indicator work theory:

The red and green gravity balls are used for the battery indicator. The gravity corresponds to cristical density of battery electrolyte, when it works, either ball sinks or gloats, leading to different indicators, meaning to indicate different battery states.

Advantages:

Determines the battery capacity at a glance.,

Basing on specific gravity, indicates stable charging state.

Provides temperature compensation to assure accurate reading at any battery temperature.

Indicate a low electrolyte level

Reduces the demands for OCV(open circuit voltage) testing, thereby saving time.

Reduces customer warranty claims.