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2017 Forester
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Discussion Starter · #1 ·
I bought my 2017 Forester Limited in August 2016 and have recently been experiencing battery issues (apparently not so unusual according to multiple threads.) This past winter, the battery went dead several times, which I attributed to cold weather and not driving it long enough distances. I started driving it more to make sure my battery had the opportunity to charge up and didn’t have any further issues until about 2 months ago. It went dead once, and a few days later, I drove it 70 miles and parked, but it had a really hard time starting up again. I bought a brand new battery, and thought that should fix the issue. However, two weeks ago I left my car while I went on vacation, and upon returning, found that the battery was so dead, not even my unlock button on my key fob would work. In two weeks, my battery drained completely.

I took my car to the dealership today to see if they could diagnose the issue, and was told my alternator is bad. So I have a few questions.
1) I have read a bunch about battery issues in 2017 models, but haven’t seen anything about the alternators being the cause. Is it common to have an alternator go bad in 3 years? (Sure feels like it should last longer.)
2) If I’m having this issue now, what’s the likelihood that it will repeat itself in the next 3 years?
3) Could there be anything else causing these issues instead of the alternator? It’s a lot of money to fork out for an alternator, if the root cause is something else.
 

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2015 Forester 2.5i Limited CVT
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1,489 Posts
The alternator is a root but it shouldn’t go bad after few years. We have a 2003 Forester with the original alternator. Check the battery cables. Please let us know how this turns out. Good luck.
 

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2017 Forester Premium CVT
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68 Posts
My '17 was diagnosed with a failing battery (hydrometer test) at 48K by the dealer during the PMCS visit. He suggested a replacement, ~$125. I was noticing sluggish starts, so I replaced with a Everstart given that the OEM battery failed at two years.

I know from experience that a weak battery can wear out a alternator prematurely, hence my decision to replace immediately.
 

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2017 Forester Touring CVT
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13 Posts
I just replaced the battery on our 2017 Forester Touring, I've lost count on the number of times I have had to jump or charge the battery, the original is known to be Marginal in size so I got the largest Diehard the car would take, by the way it has 24K on the odometer. Hopefully this will solve the problem.
 

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2001 Forester S, 4EAT
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2,881 Posts
222,250 miles on miles 2001 Forester. Still factory alternator, and I have never let any of the batteries failed. I always replace the batteries in 2-3 years (Flood Lead Acid) or 5-6 years (AGM). Many owners here insist on getting the Subaru battery replaced under warranty to only have it fail again, IMHO pointless. Just get an AGM battery and get on with life. Having batteries fail is a great method to kill the alternator as you are forcing the alternator to bring a dead battery back to life after you jump start the vehicle. Alternators were never designed to recharge a dead battery....
 

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2017 Subaru Forester CVT 2.5i Touring
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19 Posts
I've lost count on the number of times I have had to jump or charge the battery
I was eating up batteries as well, and found that I had a short in the ECM for the remote key system that was drawing too much power even when the car was turned off.

I’ve also read of others having similar symptoms due to other ECM units incorrectly drawing power.

I mention this because even though this thread is about alternators, the root cause of some of these issues could be a zombie power draw coming from one or more of the vehicle’s control units.
 

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2017 Forester Touring CVT
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13 Posts
I'm hoping that the new battery will help solve our problem, our previous Camry handled my wife's short stop and go trips.
The Forester's OEM battery seemed to have a very low reserve and previously on this site a number of owners were complaining about the size of the battery, it was small. I installed a DieHard Platinum Battery, BCI Group Size 35, 585 CCA, 730 CA, 100 RC, previous was much smaller. I'll remember what you said about the ECM, there is a proposed
problem of battery drain being suggested for a recall, definitely watching that since I'm out of warranty.
 
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