Remember this is a very rough estimate. A battery that is only half empty will take less time. Because the current drops near the end of the charge, it might take a little longer.

After the charger shows a green light, wait 30 minutes, then measure battery voltage:

Connecting the clips to the battery in the correct order is crucial for safety.

This can be normal. The ammeter is your primary indicator. A low ammeter reading (e.g., near 1) with two lights illuminated can indicate a fully charged battery.