How Long Do You Charge an OPTIMA Battery?

Tips & Support
OPTIMA Batteries
Elkhart Lake, Wisconsin

A little bit of math may need to be involved, when trying to answer the question of how long you should charge an OPTIMA battery. OPTIMA Chargers & Maintainers are fully-automatic and can eliminate the need to do any math, by charging your OPTIMA battery (or any 12-volt lead-acid battery) for only as long as they need to be charged. If you don't have an OPTIMA charger and aren't planning on getting one anytime soon, we'll give you some general guidelines for how long you may need to charge your OPTIMA battery.

Fully-charged, OPTIMA REDTOP batteries (and the 34M BLUETOP) will measure about 12.6-12.8 and YELLOWTOPs will measure about 13.0-13.2 volts (and BLUETOPs, except the 34M). Knowing your battery's voltage will give you a good idea of how long you will need to charge your OPTIMA battery. 

If a REDTOP measures about 12.1 volts or a YELLOWTOP measures about 12.3 volts, it is about 50% discharged. When a REDTOP measures about 11.2 volts or a YELLOWTOP measures about 11.3 volts, it is considered 100% discharged. We mention that, so you can have a reasonable understanding of the relationship between the voltage level in a battery and the battery's state of charge, as we don't want someone thinking a 12-volt battery that measures 6 volts is only 50% discharged.

Once you know your OPTIMA battery's voltage level, you should find out the capacity of the battery when it is fully-charged, which is measured in amp hours (Ah). For example, the D34/78 YELLOWTOP battery pictured above is a 55Ah battery. That means, if that battery measures about 12.3 volts, you will probably need to get about 27Ah of energy back into the battery.

From there, you should look at the rate at which your battery charger delivers current to the battery it is charging. In the above example, if we were to use a 10-amp charge rate (and we don't recommend exceeding 10 amps when charging OPTIMA Batteries), some simple math would suggest it would take almost three hours to fully-charge the OPTIMA battery.

However, that assumes the charger is 100% efficient (most are not) and would deliver a constant amount of amperage to the battery throughout the charge cycle (most do not). That does at least give you a rough estimate of the amount of time it will take you to charge your battery though. Chances are, you'll need to add some time to your estimate for most chargers, to make sure the battery is fully-charged.

While many modern chargers are fully-automatic and will only deliver the current your OPTIMA battery needs, that is not always the case. If your battery charger is not fully-automatic, you'll want to keep an eye on the battery as it charges, to make sure it is not overcharged. It's ok if an OPTIMA battery gets warm while charging, but if it begins to vent or gets hot-to-the-touch, discontinue charging immediately.

If all that math and monitoring is more than you want to sign up for, you can always pick up an OPTIMA charger or maintainer, which are fully-automatic. Not only will they only deliver the current your OPTIMA battery needs, you can leave them connected indefinitely and they will keep the battery voltage properly-maintained without any additional effort on your par.