We often hear the question of what the proper voltage level is in a fully-charged marine battery. In the case of OPTIMA batteries, there are two correct answers, because we offer two different types of marine batteries. Our 34M BLUETOP marine battery is a starting battery with a dark gray case, that is designed and warrantied for use in applications that involve starting your engine. All of our other marine batteries (D34M, D27M & D31M) are all designed and warrantied for both starting and deep-cycle applications. So what does that mean in terms of voltage levels?

Our 34M BLUETOP is fully-charged at about 12.6-12.8 volts and all our other BLUETOP batteries are fully-charged at about 13.0-13.2 volts. If you are using another brand of battery and don't know what the fully-charged voltage level should be in your battery, the safe minimum level for a fully-charged 12-volt lead-acid battery should be at least 12.6 volts. If you are running two 12-volt batteries in a 24-volt application, like a trolling motor, you'll need to double those numbers. If you are running three 12-volt batteries in a 36-volt application, you'll need to triple those numbers.

Equally as important as knowing your fully-charged voltage level, is keeping your battery fully-charged at that level whenever possible. Proper voltage maintenance will maximie the performance and lifespan of all batteries and a microprocessor-controlled OPTIMA charger or maintainer will do a great job of properly-maintaining battery voltage in any marine battery.

We're so confident this is true, we will extend the free replacement warranty coverage on your OPTIMA battery purchase, if you buy an OPTIMA Digital 1200 charger from us at the same time.