A quick and easy method for determining the amount of charge left in your caravan batteries is to look at the voltage. This can be via a handheld voltmeter, or multimeter, or a built in volt meter.
| State of Charge | Sealed or Flooded Lead Acid | Gel battery | AGM battery |
| 100% | 12.70+ | 12.85+ | 12.80+ |
| 75% | 12.40 | 12.65 | 12.60 |
| 50% | 12.20 | 12.35 | 12.30 |
| 25% | 12.00 | 12.00 | 12.00 |
| 0% | 11.80 | 11.80 | 11.80 |
