2002 Subaru Forester battery

Does a car just sitting for a few days normally lose battery power?
AAA guy said just driving to store (1 mile) will not keep battery up as uses so much power just starting it.
2nd new battery in three years.

Lead acid batteries self-discharge and so lose charge all by themselves. Your car has several computers that keep themselves alive and draw a very small amount of charge to do so. When you start the car, the battery loses another bit of charge ad then driving it makes the alternator charge the battery back up - and that takes time - so short trips of under a mile mean the battery never gets fully recharged.

There are small battery chargers available that you can have installed to keep the battery fully charged with the limited time you drive the car but you’d have to plug it in when you park and unplug it when you drive away. Or you could buy new batteries. Your choice.


There are also small solar chargers. This may work for you if you can consistently park so that sun shines in, say, the rear window on the solar panel placed there.

To a very minor extent, yes.

He was correct. In order to keep your battery charged, you need to drive much further than one mile each time that you start the engine.

That leads me to another point, namely…
Are you changing your oil at least every 4 months, rather than waiting until you reach the odometer mileage interval for an oil change? When you drive only very short distances, this takes a major toll on the engine’s oil because water vapor–which is a natural byproduct of combustion–cannot be evaporated from the oil during those short drive cycles. In addition to becoming water-diluted, the oil becomes acidic over time as a result of that dilution. Even the exhaust system will suffer an early death from being subjected to only extremely short drive cycles.

I would suggest that the OP get his vehicle out on the highway once each week for a drive of at least 30 minutes. That will help to keep the battery charged, and to evaporate the water that has undoubtedly diluted the motor oil.

1 Like

Sitting is the worst thing that can happen to a car battery. It begins to sulfate which means the acid in the battery electrolyte starts clinging to the lead plates.
Charging the battery while driving will force the acid off of the plates and 1 mile drives won’t accomplish this.

You need to use a solar charger if possible or a trickle charger to keep a tiny amount of current flowing through the battery or short lived batteries is the option.

1 Like

Yes, that’s true. I wouldn’t expect that would ruin the battery in 1 1/2 years though. Although it might discharge it enough it sometimes won’t start the engine, especially in cold weather. Why are you replacing the battery rather than just charging it with a battery charger? Was there testing done which indicated the battery was faulty and incapable of being recharged?