Using a 12 volt battery full of charge let’s say … 120 amp/hours.
If we measure the voltage of fully charged 12 volt battery with nothing connected it should be around 12.6 volts.
If we connect a reasonable load to the battery the voltage will drop to around 12.1 but the battery is still full of charge at this point.
If we connect a charging source to the battery, for example an 80 watt solar panel, the voltage will rise to about 15 – 16 volts.
If the battery was flat we might see the following:
- No load: 12 volts
- With load: 11.0 volts
- Charge connected: 13 volts