Battery Usage
As hard as starting an engine is, letting the car sit isn’t good for the battery, either. Part of that is because a battery will naturally discharge over time, and starting the car activates the alternator, which recharges the battery as you drive. (Note that the alternator also has to power all the devices used when your car is running, and as the alternator doesn’t put out if any, power when the engine is idling, it won’t recharge the battery much on a short drive.) But on modern cars, there’s another problem.
There are many computers and electronic devices in newer cars that require battery power to keep their memories alive, and they draw power even when the car is “off.” For instance, for an in-car equipped with remote locks, there’s a little receiver constantly “listening” for a radio signal from your key fob, and that receiver draws its power from the battery.
Car Battery Care
It’s not good for a normal lead-acid battery to be kept discharged (though AGMs aren’t as sensitive to this), so even if the battery isn’t “dead” when you try to start your car after a long period of sitting, it wears on the battery. If the vehicle has been sitting for a long time, try to drive it awhile — ideally on the highway — to fully recharge it.
Suppose your car often goes unused for long periods. In that case, you might consider using what’s called a battery maintainer or“battery tender, which hooks up like a battery charger but is designed not to overcharge the battery — which a battery charger can do if you leave it on too long. Note that a maintainer is not good for charging up a low battery; it only keeps a fully charged one at its peak.
Extreme temperatures also affect a battery’s life. While we often think of cold weather as being hard on a battery, and it does indeed reduce its power, heat is worse for longevity. Keeping your car in the shade during the summer (or garaged year-round, ideally) is an advantage.