Subaru Forester Owners Forum banner
21 - 40 of 54 Posts

·
Registered
15 Toyota Avalon hybrid; 02 Honda Odyssey
Joined
·
64 Posts
So, in suggesting that 11,000 might be a typo for 1,100, I'm not being literal enough. But in taking "impossible" to mean impossible, I'm being too literal.

Like being in a Lewis Carroll story......
 

·
Registered
Joined
·
8 Posts
Dead batteries are no fun. back to back days..Lots of advice in front of me.. first step is battery health check.. then go from there. My battery story.. I have 2019 Forester with ~23k miles on it. Battery would die in 5-7 days of no use. Dealer checked and said it was fine. I saw a post somewhere that suggested the key fob could drain the battery if it was stored too close to the car. I bought an RFID shield/faraday pouch to keep my key fob's in and have had zero issues since.
 

·
Registered
2019 Forester Touring Continuously Variable
Joined
·
22 Posts
The OEM battery in my 2019 Forester Touring began to die on me after 15 months or so. After needing several jumps (fortunately, all in my driveway) I replaced it with the Interstate MTX-35 AGM. I didn't want to face a winter with a dicey battery, and I've had no issues with the Interstate.
 

·
Registered
Joined
·
6 Posts
On my 2019 Forester Premium, I had a dead battery problem. I had about 3500 miles on my vehicle. I took it to the dealership, and my battery was replaced (so I thought). When I got home, I checked and found they installed a regular battery which was the wrong type. These newer Foresters and some other models require an AGM battery. I had some help from the Subaru Customer Advocacy Dept. There was a class-action suit against Subaru for bad batteries. I also checked with other Subaru dealerships. I was told that my dealership was required to provide the correct AGM battery at no charge. Apparently, some Foresters had the same battery problems as other late non-Forester models. My dealership told me that they were unaware of the Subaru program for battery replacements. They apologized. I was very persistent in my actions. So far, my new AGM battery has held up quite well. However, I do take intermittent battery checkups with a multimeter to ensure the correct voltage holds up. Also, I bought a new battery charger specifically for charging AGM batteries. My older slow trickle charger could have worked, however, it would have taken much longer for a full charge. The parts dept at my Subaru dealership submitted the VIN number to a specific Subaru administrative office, and they had no problem in obtaining the new AGM battery. I thanked the Subaru Advocacy Dept for their help. All was done via email with them.
 

·
Registered
2009 Forester 2.5X
Joined
·
149 Posts
My '09 is the only vehicle I'ver ever owned that seemed to kill the battery for no apparent reason. I think I'm on my fourth battery now (Interstate brand). Mine will be fine for weeks or months, then suddenly be completely dead overnight. I put a pigtail on it for a battery tender and use it all winter.
 

·
Registered
2021 Forester Limited
Joined
·
340 Posts
I do not know this for a fact, but I suspect Subaru utilizes a dual mode charging system.
The ECM/PCM whatever you choose to call it, can vary the alternator field winding current to control the target voltage depending on the electrical load, battery temperature, etc.

The simpler/older set ups mostly varied the voltage/charging rate by an ambient temp sensor near the battery. But I suspect newer systems will go with a lower charge rate if there is no significant load to increase fuel economy. It basically uses target voltage to control the amperage output. If it wants to raise the voltage, it adds volts to the field winding, which increases amperage. And vice versa.

So it is really one broad mode, it just depends on what inputs the PCM sees, and adjusts accordingly.

Even driving with the lights on, to increase voltage, will only work until the ambient temps at the battery temp sensor get to a certain point. If it thinks the battery is getting too warm, it will back down current flow to keep from overheating the battery.

My '99 Jeep would have about 14 volts in the summer, and 14.5 volts in the winter. So it definitely dropped the charging rate in the warmer months.
 

·
Registered
2021 Forester Limited
Joined
·
340 Posts
These newer Foresters and some other models require an AGM battery.
The '21's come with an enhanced flooded cell battery. There is no AGM battery from the factory. If it had an AGM, it would not crap out so soon. I suspect it is the same for '19 and '20. Not sure where it says an AGM is "Required" because they don't come with them installed. "Recommended" Most certainly.
 

·
Registered
Sahuarita, AZ 2018 Forester Limited
Joined
·
2,969 Posts
After needing several jumps (fortunately, all in my driveway) I replaced it with the Interstate MTX-35 AGM.
Although the factory battery on my 2018 is still performing well at 73k miles, I recently picked up an Interstate group size 35 AGM battery when I saw it back in stock at Costco. I live in the hot desert Southwest which is tough on flooded batteries and I suspect my factory battery will crap out before it reaches 4 years old. I've been maintaining it distilled water top offs annually and putting it on a battery tender every 6 months or so.
 

·
Registered
2019 Forester Touring Continuously Variable
Joined
·
22 Posts
@ForesterBill,
It's cheaper at Costco but the nearest one to me is a 75-mile roundtrip so I bought it locally. I lived in Glendale forty years ago so I know what Arizona heat is like! It doesn't get so hot here in the Hudson valley but it can get plenty cold in the winter. Two things that I don't believe in skimping on are batteries and tires. The peace of mind is worth the cash outlay to me.
 

·
Registered
Joined
·
6 Posts
My owner's manual specifies a Q85 battery which translates into an Enhanced Flooded Battery (EFB). When I googled Q85, it brought up about five different AGM batteries from different auto parts suppliers. My understanding the need for such batteries is because of the electronics drain on these newer Subaru models.
 

·
Registered
2021 Forester Premium
Joined
·
24 Posts
The ECM/PCM whatever you choose to call it, can vary the alternator field winding current to control the target voltage depending on the electrical load, battery temperature, etc.
Thank you for that explanation. That helps my understanding a bunch. (y) The battery in my '21 is the Q85 enhanced flooded cell variety, not an AGM. So knowing all that, along with the OP's experience, its obvious now the battery in this new Forester is not a "set & forget" kinda thing. It will need periodic monitoring, especially in light of all the fancy electronics Subaru installed on the car.

If I had an accurate clap meter I'd love to see what the Forester's natural current draw is when the engine is off overnight. I owned one of those problematic Honda CRV's that another poster referenced earlier. The natural draw on that car was 65 mAs, which goes a long way explaining why the battery tester said to recharge it when the car wasn't driven for 3 or 4 days. My old Pilot only had about 10 mAs draw and it's battery lasted 5 years. The battery on my son's plain jane '14 Outback lasted 6 years. So I am suspicious of the added load on the battery that all these new fancy electronics might have which are being installed on cars these days. Nonetheless it is a fun car to drive.
 

·
Registered
2021 Forester Sport
Joined
·
8 Posts
My 2021 Forester battery was dead two mornings in a row this week when I tried to leave for work. My VIN begins with a “J” which I am told means that it was manufactured in Japan. I bought the car new exactly 6 months ago and only have 11,000 miles on it. I’ve been made aware of battery drain lawsuits on older models but is it an issue for anyone with a 2021 model? I’ve also been told that only the models made in America are problematic and the Japanese ones don’t have the same battery issue. Is that true? I never leave the back hatch open. I only drive back and forth to work or run errands with it. Suggestions?
You most likely just have a bum battery. Save yourself more aggravation and just go buy a brand name battery and be done with it.

LOL....it's funny you mention this being made in Japan. That is why I will only buy a Crosstrek or Forrester. Because they are made in Japan. I don't have any faith in unionized American auto workers. I'm pretty sure we will less quality issues then the Subarus built in the US.

-Keith
 

·
Registered
2019 Touring
Joined
·
252 Posts
I would do several things. First, after the car has been sitting for a while, check to see if there is any battery draw. This is not too hard to do and YouTube can help. Second thing is to add an auto stop eliminator. Third is probably most important, regardless of the first two and that is to add a battery conditioner, not trickle charger. Put a pigtail on your battery and have the lead available through your radiator. When your car is sitting in the garage, just plug it in. It will sense voltage of the battery and keep it fully charged, but not over cooked. I do this for my motorcycle and eaisly get 3-4 years on a battery in Florida. The heat is the problem and shortens battery life.
 

·
Registered
2021 Forester Touring (Canadian version)
Joined
·
204 Posts
Exactly what I did for my 2021. Added an auto stop eliminator, added a CTEK battery conditioner with the plug coming through the grill (needed to purchase the extension cable for this). Just keep it plugged in all the time when not in use. I often leave the unused for 2 or 3 weeks at a time and have had zero issues.
 

·
Registered
2019 Forester Limited
Joined
·
1,211 Posts
While y'all are waiting for @HCK to check back in...

The rear cargo incandescent bulb is a 13 Watt bulb that draws about an amp, and will deplete a new and fully charged battery in around 60 hours. I learned it can make for difficult starting much much sooner.

I bought myself some peace of mind, and replaced the stock bulb with a diode dynamics 194 HP5 bulb. (194 HP5 LED Bulbs). Kinda pricey, but it reduced the current draw from about 1 amp to about 0.08 amp.

@Oldguy2 - Parasitic current draw for our foresters is specified at a maximum of 70 milliamperes. My 2019 measures around 35.
 

·
FOTM Moderator
2014 2.5i Limited CVT
Joined
·
3,449 Posts
I replaced all of my interior (and really, exterior) bulbs with some type of LED bulbs...

But I also make sure the lights are out when I lock up the car at night...
 

·
Registered
2021 Forester Premium
Joined
·
24 Posts
Thanks boureesub. Considering the robust discussion HCK started with this thread I hope he lets us know how he made out too. :)

70 mA's seems like a lot to me, but I guess I am not surprised. If one does the math it means the fully charged 62 Ah battery in my Forester would be drained in about 37 days ... (0.070 draw x 24hrs = 1.68 Ah per day) and ( 62 Ah / 1.68 = 36.9 days). And if the battery is less than fully charged, like around 12.4 volts, it can make for difficult starting much much sooner as you pointed out. Assuming my math is correct I guess it simply reinforces what we all know already ... make the kind of LED bulb changes you did, or keep an infrequently driven car's battery as fully charged as possible with a battery conditioner or maintainer as you can.
 

·
Registered
2021 Forester Sport
Joined
·
66 Posts
Exactly what I did for my 2021. Added an auto stop eliminator, added a CTEK battery conditioner with the plug coming through the grill (needed to purchase the extension cable for this). Just keep it plugged in all the time when not in use. I often leave the unused for 2 or 3 weeks at a time and have had zero issues.
I'm thinking about adding the auto stop eliminator however, like @zcrow, I installed a connector plug to my battery so that I can, at anytime plug in my CTEK Smart charger to keep my battery topped off.
Motor vehicle Electrical wiring Automotive exterior Auto part Wire
 
21 - 40 of 54 Posts
Top