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2009 Subaru Forester on its 3rd battery

I bought the car brand new in May of 2009. All was good until February of last year when the battery died. Since I live in Anchorage, AK, and we were in the middle of a good cold snap, I kind of wrote it off as one of those things that’s part of life in AK. But then the same thing happened in November - yes, it was cold again, but it died after I’d successfully started it and drove it to my husband’s work. He was inside for maybe thirty minutes. Not wanting to waste gas, it turned the car off and listened to the radio. When hubby came back, I tried to start the car and … nothing. We had to get it jumped. Hubby said I shouldn’t have been listening to the radio with the engine off. (For maybe 20 minutes? Really??) Anyway, I had a service appointment at the dealership a few days later and mentioned that the battery died again. They checked it and said it was weak so they replaced it.

Now, of course, I’m super-paranoid about everything that could be draining the battery. I turn the lights off whenever I turn off the engine (even though that’s supposed to be something the car does automatically), and only listen to the radio when I’m driving. I’ve made sure that there’s nothing plugged in any of the power outlets, and I don’t have anything that’s after-market. Oh, and middle of last year the radio/CD player died too, and that had to be replaced. Don’t know if it’s linked, but it’s still odd.

The only suggestion the dealership had was to drive it more. I guess I’m pretty severe on the car - work’s maybe a fifteen minute drive (20 if it’s snowing) and a fair few of my journeys are short ones, for a variety of reasons. Plus, it’s Anchorage, AK. Severe driving’s standard here. But I never had these issues with my other cars, and my driving patterns haven’t changed at all. Could there be something that’s draining the battery that I haven’t thought of, or am I really stuck with driving around Anchorage aimlessly for at least 20 minutes each time I get in the car?

If this happens again, you might look into getting a battery with a higher reserve capacity. I don’t know what your Subaru calls for, but the stock battery might be a little undersized for that climate. Also, maybe try another brand of battery. While it’s true that there are only a few manufacturers in the US, there is a store near me that’s notorious for selling lousy batteries. Not sure who makes the batteries for them, what they do that’s different, but everyone I know that’s had a battery from them has had to replace it prematurely.

In the cold AK climate, especially since you are probably driving with your headlights on for a good chunk of the year, and no doubt the heater/defogger/fan/wipers a lot, you do indeed need to give the car a good run a couple times a week to make sure the battery stays charged. If you have a source of electricity handy near the car, it might be worth getting a “battery tender” or a small charger. You could probably keep it hooked up and just plug in the car when you don’t get a chance to drive it much or know it’s going to be sitting overnight on a particularly cold day. A block heater of the type that goes in the oil dipstick tube might not be a bad idea either. I’m assuming you already use full-synthetic oil in the car, based on the climate. If not, you should be.

Seems odd. It certainly doesn’t get as cold as Alaska as it does here in New England but Subies tend to be the weapon of choice for lost of people because of its reliability in bad weather. You see them everywhere here.

Does the car crank but not start? If it turns slowly or not turn at all, it could be that your oil is too thick. Subary recommend 5/30 but there is a lower viscosity oil that may actually work better in really cold climates, like 0/30.

Cold decreases the peak capacity of the battery but one would imagine that it should start fine after leaving it for a half hour. Oblivion’s suggestion is a good one, to find another battery. Some are better than others at performing in cold climates. Some are actually made to perform in cold weather.

If you or your husband knows how to use a multimeter, perhaps see if you can hook it into the a fuse somewhere and monitor the voltage while you’re driving. It should be around 14.4 V while driving.
If it isn’t, your battery isn’t being charged properly.
Make sure you drive the car a bit every day. Blow the spiders out of the exhaust by running it a bit of a distance. If it is a stick, rev the engine a bit higher by running in a lower gear. It will make sure you charge your battery but also blow some of the water out of the exhaust system - this is unrelated to your issue but that will help slow the rusting process of the exhaust.

Twenty minutes of radio time or a few minutes of headlight operation on a non-running engine should not run down a good battery.

Question though. You state it was fine and then nothing. By that do you mean there was absolutely no click sound, slow starter motor operation, etc?
If this car has an automatic transmission maybe there’s a fault with the neutral safety switch; sometimes called a range selector switch.
This is the device that prevents an engine from being started in anything other than PARK or NEUTRAL.

Do you do a lot of driving on washboarded dirt roads?? The vibration and pounding will greatly shorten battery life…

Yes, you may have a “phantom drain” pulling a small amount of current from the battery even when the ignition is off. I just had that problem on my van. If you or your husband have a voltmeter and know how to use it, you can easily test your system for a current drain at the battery. Or a local mechanic can do it for you.

The dealer should have tested your system for the current drain, but apparently they didn’t.

Here’s how to do that test:

I have to wonder if the alternator is producing the rated output it is supposed to have. It may not be charging the battery to the proper capacity or there may be some resistance in the charging lead. The alternator may also be producing AC ripple voltage due to bad diodes inside it. Any of these things could cause the trouble you are having. The shop should have checked these things out but it appears you still may have some trouble. I see you live in the neighborhood (Anchorage) so if you would like me to check these things out send me a PM and we’ll see what is going on. Having that many battery issues is not right.