Why Does a Car Battery Drain Even When Not in Use?

Why does a car battery drain even when not in use
SponsorOPTIMA Battery Chargers
LocationMilwaukee, Wisconsin
DateApril 7, 2021
Whether someone is returning to a car parked at the airport after a long trip or taking a car out of winter storage, those cars often suffer from the same issue- a dead battery. Why does this happen? Well, all batteries have a self-discharge rate, even if they aren't connected to a vehicle or anything else that might draw current.

For example, a fully-charged OPTIMA battery can be stored for up to six months without issue in a cool, dry location. However, if the battery isn't fully-charged when it goes into storage or is subjected to extreme temperatures (either hot or cold), that timeframe may be shortened significantly. When batteries are connected to a vehicle or something else that drains current from them, the discharge process can accelerate significantly. This is especially true for vehicles equipped with car alarms or satellite-based systems that actively look for or maintain a connection, even when the vehicle is not in use. That is also true if your vehicle's key fob activates the vehicle's computer system when it gets within a specific range of the vehicle...and you leave your key fob in the car.

Other electrical accessories, like seat position memory or radio presets can also slowly drain a battery, but the cumulative outcome in all of these scenarios is that sooner or later, the battery will become completely drained. What can someone do to prevent this from happening? A couple of things.

The most-obvious option is to make sure the battery is fully-charged and disconnected, if a vehicle is going to sit for an extended period of time. If that's not possible or practical, another option is to use a quality battery maintenance device while the vehicle is in storage, like the OPTIMA Digital 400 or Digital 1200 chargers and maintainers. These chargers will keep your battery fully-charged and ready to use, they can be connected to the battery indefinitely and they are very easy to use, even for someone who doesn't know anything about cars.

So what do you do if you're reading this because your battery was already drained? Fully-charge your battery to at least 12.6 volts, as soon as possible. We mention 12.6 volts specifically, because a lot of people mistakenly believe a 12-volt battery is fully-charged at 12.0 volts, when that is definitely not the case. In fact, whenever any battery is drained below 12.4 volts and is left sitting in that state, sulfation will begin forming in the plates. That sulfation diminishes both battery capacity and battery lifespan. That makes a quality battery maintainer an investment that will pay for itself over the life of all your vehicles.