Optima Batteries Explains Why 12.4 Is Your Battery’s Magic Number

Technology has changed a lot since our cars first started rolling off assembly lines. The amount of electronics today is staggering, and the batteries in our cars are required to do more than simply get the engine going. Power demands have become more specialized and our car’s electronics have adjusted to meet the demand, but there are still a few facts that remain.

Battery construction has changed a lot in recent years, but since the jump from six volts to one dozen, the power requirements have remained relatively constant. But what is the BEST voltage for your “12-volt” battery? As we all know, the voltage will fluctuate depending on use.

An Optima Battery's six cells are comprised of lead, wrapped in fiberglass matting that serves to separate the positive and negative parts of the cell. The glass matting also absorbs the electrolyte, hence the term Absorbed Glass Mat or AGM.

Optima Batteries gets that question often, and they’re working hard to get the right information out there to help prolong the life of any battery. They have even devoted a section of their YouTube channel specifically for the technical side of battery care. There are a few things you should know before we get into the “perfect” scenario for your battery’s voltage. First, while your battery is called a 12 volt battery, if it has only 12 volts, it is significantly discharged. Every 12 volt battery is comprised of six cells that produce roughly 2.2 volts per cell. Do the math, and that means your “12 volt” battery should have 13.2 volts, much more than the advertised 12.

Since batteries store energy and their voltage will fluctuate, is that the BEST voltage to keep it? Unless you’re driving your car regularly, every battery will lose a charge over time. Also, even small drains such as your radio’s memory feature or various other systems will wear down a battery over time.

How Far Is Too Far?

Optima’s parent company, Johnson Controls, manufactures both Flooded Lead-Acid batteries and the spiral-wound Absorbant-Glass-Mat (AGM) Optima brand batteries. While the design of each differs, they still have the same voltage recommendations for long life. Optima recommends that a battery’s voltage should not drop below 12.4 volts, as that is the voltage when sulfation begins to occur internally within the battery.

Optima offers two different chargers that will work on any 12 volt battery. They use micro-processors to constantly regulate the battery’s voltage and have settings for various types of batteries, AGM or flooded-lead-acid.

Sulfation builds up over time and eventually, will diminish a battery’s performance and life span. The best way to prevent that is to keep a battery’s voltage above 12.4 volts. Many chargers, such as Optima’s Digital 400 and Digital 1200 chargers use micro-processors that constantly regulate the voltage of your battery and keep it in a state of readiness, even with the common draw of station presets and various other normal voltage drains of today’s cars.

The Digital 400 is smaller and works great as a charger and maintainer, while the Digital 1200 does both tasks equally well. The Digital 1200's larger size also includes a higher charging amperage of 12 amps max. compared to the Digital 400's 4 amps max.

If you don’t have a self-regulating charger, you can also use an analog style charger but would need to regulate the battery’s state yourself. Don’t leave a standard, non-regulated charger on any battery for an extended amount of time, as it could eventually overheat the battery and ruin it.

Analog chargers can be used to charge any 12 volt battery, Optima included, but may not recognize a deeply discharged Optima battery below 10.5 volts. Also, for charging a 12 volt battery, Optima suggests a max of 10 amps at around 13.8-15 volts. For float charging, they recommend 1 amp at 13.2-13.8 volts. Both Optima chargers automatically regulate the charging amperage and adjust between charging and float charging (maintaining) a battery. They also have various settings for different types of batteries.

Instead, keep an eye on your battery’s voltage and when you see it drop to 12.5 volts, simply hook up the charger and bring it back to full charge. You could also disconnect the battery if you are not planning on using the car for some time, perhaps over the winter. This will help limit the draw on the battery.

Even if you’re going for a vintage vibe in your ride, you can still enjoy modern technology with some ingenuity!

Also, starting the car and running it for a short time may help scratch that itch of hearing your exhaust and that amazing, performance camshaft, but it doesn’t help the battery as much as you might think. Starting the car takes a significant amount of a battery’s capacity, and without running consistently at higher rpm, the alternator may not produce enough energy to replace even what was used to start the car. Thereby leaving your battery in a worse-off state than if you didn’t start the car at all.

We are huge proponents of driving your car, which is the best, and most fun way to keep your battery at optimum voltage!

We’re huge proponents of driving our cars, and with a properly-working charging system, will keep your battery charged up. But if that’s not an option, then keeping your battery in mind will help ensure that it’ll be ready whenever you are.

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About the author

Andy Bolig

Andy has been intrigued by mechanical things all of his life and enjoys tinkering with cars of all makes and ages. Finding value in style points, he can appreciate cars of all power and performance levels. Andy is an avid railfan and gets his “high” by flying radio-controlled model airplanes when time permits. He keeps his feet firmly grounded by working on his two street rods and his supercharged C4 Corvette. Whether planes, trains, motorcycles, or automobiles, Andy has immersed himself in a world driven by internal combustion.
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