Open circuit voltage vs state of charge

Checking your battery's voltage with a digital multi meter can give you a good indication of how much charge is left.

For the most accurate reading, the battery should be at rest. That means the engine should be off, the charger disconnected and the battery left to settle for a short time before testing.

As a general guide, a fully charged 12-volt lead-acid battery will usually measure around 12.7 volts. At about 50% charge, it may read around 12.2 volts, while a reading below 12.0 volts generally indicates the battery is heavily discharged.

It's important to remember that voltage only tells you how much charge is in the battery, it doesn't tell you how healthy the battery is.

A battery can show a good voltage but still fail when asked to start an engine because its internal capacity has deteriorated with age.

That's why a professional battery test is the best way to understand your battery's condition.

Free Testing

Battery Town offers free battery testing at locations across New Zealand. Our trained technicians can check both the battery's state of charge and its overall health, giving you confidence that your battery is ready for the road or letting you know it's time to replace it before it leaves you stranded.