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2011 Forester
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10 Posts
Discussion Starter · #1 ·
Hi everyone!

My 2011 Forester has always had some trouble starting, particularly in cold, humid weather. The Subaru dealership replaced the battery once on warranty, because apparently it wasn't holding charge - and that was when I was driving the car daily. Now, due to changed circumstances, my Forester sits parked for sometimes weeks at a time. It drained its battery over the summer (no life at all when I tried to start it) after sitting for about a month. I had it boosted and then made an effort to drive it regularly during the fall. I've been away on business for 2 months this winter, but had someone start my Forester every 2 weeks and run it for a while. I just returned and discovered the battery drained again, even though it apparently started fine 2 weeks ago. I tested the battery this time and it was at 11.6 V - enough to turn lights on and make the solenoid click but not to start the engine. I have a 2009 Toyota that also sits for the same extended periods, and it has never had issues with starting or with a drained battery.

I'm hoping this issue can be attributed to the Subaru OEM batteries, and that replacing the battery with a different brand will fix this issue. Can anyone recommend a battery brand/model that would be better suited to my intermittent driving habits and also be able to withstand cold Alberta winters? Or provide me with the specs that I should be looking for in a replacement battery? Can anyone also confirm whether the Forester has a particularly aggressive key out battery draw, as it seems odd to me that the Subaru (Subaru battery?) drains so much more quickly than my Toyota.

Any advice is greatly appreciated! When I do drive my Subaru now, it's mostly in the winter to remote areas - so it would be a huge load off my mind to solve this issue!
 

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2018 XT Touring CVT
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1,297 Posts
Get an AGM dual purpose battery, as in starting and deep cycle.
The Optima Yellow top is one example.

Use a solar or plugin trickle charger.
Error on the side of too small rather than too large of a plugin charger output to avoid overheating the battery.
A solar charger in an Alberta winter is unlikely to overheat a battery, go large since the ratings are very optimistic on solar chargers.

Clean the battery with water to eliminate tracking paths.
 

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2010 2.5X Limited 4-speed Auto
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1,979 Posts
Personally, letting a battery go two weeks between uses it a week too long, especially in cold weather. In addition, just starting the vehicle and letting it run for a few minutes will do nothing to keep the charge level up. The vehicle needs to actually be driven, and then for at least 15 minutes at a reasonable speed.

If you are unable to do that, then you need to put it on a trickle charger in between that two week period.

If you want to replace the battery, get something with at least a 500 cold cranking amps rating.
 

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2012 Forester 4 speed auto
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1,151 Posts
Battery switch

Install a battery switch which will convienently disconnect the battery. You can pick one up at any auto parts store. I use one when I travel and my Forester sits for weeks at the airport. When I get back I simply pop the hood and turn the switch and I am going home!
 

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2018 XT Touring CVT
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1,297 Posts
A battery switch will work if the battery is good, and clean.
You will need to reprogram your radio presets each time, and the alarm will be off.
A solar trickle charger is less work.
 

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2010 2.5X Limited 4-speed Auto
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1,979 Posts
Install a battery switch which will convienently disconnect the battery.
Simply disconnecting the battery is much cheaper and requires no wiring. :new_multi:

You will need to reprogram your radio presets each time, and the alarm will be off. A solar trickle charger is less work.
Solar isn't much good in a garage. :raspberry:
 

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Automotive Lighting Experts
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936 Posts
I suggest purchasing a battery tender, or replacing your battery with an AGM battery.

I've had an Optima Red Top in my car for several years now and never had any issues. Even with extreme climate changes (Midwest)

Nick C.
 

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2011 Forester
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10 Posts
Discussion Starter · #8 ·
Hi everyone!

Thanks for all of the great advice, I have a lot of Googling to do! I did a quick search for AGM batteries, and this definitely looks like a good battery solution for me. I've found a retailer of Optima batteries in my area, but haven't been brave enough to call and find out the price yet..

I had the Forester boosted yesterday and the AMA guy, like a lot of you, also suggested disconnecting the battery if I'm away for an extended period. He said that the battery could discharge fully and then freeze up if kept connected, which would be bad news. I will definitely take this advice on board for next time.

I should have also mentioned that my cars sit outside in a multi-dwelling parking lot, which is why we opted against a trickle charger. My partner had suggested purchasing one, but with so many people moving around the cars, shoveling snow, etc, we ultimately decided there was too much risk of the charger getting damaged or knocked loose.

Yesterday I also found out that while we were away the Forester was run more often than my Toyota. The person doing this for me was running both cars for about 30-45 min every 2 weeks - except for the week before we got back when they didn't turn the Toyota on because it was low on fuel and there was a warm snap in the weather. So the Toyota sat a lot longer without running and yet its battery tested ok at 12.5 V and it started perfectly. Thinking back, I've actually left the Toyota before for over 3 months while I was overseas and didn't have anyone to run it for me then (summertime though), and it also started fine. Not sure if this is something to be concerned about, or if such differences are normal between car makes/models?
 

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2018 XT Touring CVT
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1,297 Posts
A trickle charger can be very small and waterproof. Mount it under the hood using cable ties and it is safe from damage. Mount a 3 ft cord to connect it to your extension cord. This is what I did on my Foz.
 

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2020 Forester
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67 Posts
Personally, letting a battery go two weeks between uses it a week too long, especially in cold weather. In addition, just starting the vehicle and letting it run for a few minutes will do nothing to keep the charge level up. The vehicle needs to actually be driven, and then for at least 15 minutes at a reasonable speed.

If you are unable to do that, then you need to put it on a trickle charger in between that two week period.

If you want to replace the battery, get something with at least a 500 cold cranking amps rating.
Be sure to compare batteries using CCA and not CA. CCA are measured at 0 degrees F. while CA are measured at 32 degrees F. The difference can be as much as 100% depending on the manufacturer. It sounds like you have already killed the OE battery. To be sure, you can check the electrolyte level by looking through the side of the case. You can also check the specific gravity with a hydrometer since the caps are removable. (neither of which is possible with an AGM battery)
 
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