Use the sight glass on the top of a maintenance-free battery to gauge the (SoC) state of charge. Typically a light green dot indicates a fully charged battery. ... A dark green/black indicator on a maintenance-free battery typically indicates that the battery needs a charge.

What indicates the battery is charging properly?

Battery Tests

A reading of 12.66 volts indicates a fully charged battery. If the reading is 12.45 volts or less, the battery is low and needs to be recharged.

How do I know if battery is charging?

A fully charged battery will typically display a voltmeter reading of about 12.6 to 12.8 volts. If your voltmeter is showing a voltage anywhere between 12.4 and 12.8, that means your battery is in good shape.