Subaru has not change battery sizes from Group 35 to anything else as far as I know. It's always been Group 35(1998 onwards), some here have done some fancy work and squeezed a Group 24 in as it's slightly larger with more capacity. Also switching to Group 34 will result in the battery posts on the wrong side so you would need to replace cables as well....

 

Thank you for confirming @bman400 - much appreciated.

Would you be able to provide any documentation for reference? I was talking to a guy at AAP and he was skeptical that the optima redtop-35 would fit (https://shop.advanceautoparts.com/p/optima-red-top-battery-group-size-35-720-cca-35/16940003-P?navigationPath=L1*14920|L2*15000|L3*15597)

 

For what it’s worth, my 2019 owners manual says battery type Q85.

 

@akc5247 Can you snap a picture of your existing battery and cables? That will help, but if memory serves me correctly the skepticism regarding the Redtop-35 is due to the distance the terminals are from the Long Side of the battery and therefore necessitating stretching the cables a bit to reach the battery terminals.

@FelineFreddie I just googled Q85 batteries and they are the same as the Group 35. Not sure why Q85? Other than to signify it's for Start/Stop Systems on the vehicles. Just seems like everyone wants to add more the the confusion

 

Here you go. i see Q85 in the battery as well.

 

Group 35 is fine... Northstar Grouo 35 AGM is an incredible battery. You could also do a Group 24F (F is important means the terminals are correct for this application).

I plan to upgrade to a Northstar Group 24F AGM, but I’ll have to modify the battery tray and tie down set up... but the cranking capacity is almost double.

Don’t be too worried about the “start stop” capabilities of the Subaru factory battery... it’s a sub par battery that is better than a normal flooded lead acid, but not as expensive as AGM. It’s undersized for the job, in my opionion. Keeping the battery lightweight and inexpensive keeps manufacturing costs down.

 

Group 35 is fine... Northstar Grouo 35 AGM is an incredible battery. You could also do a Group 24F (F is important means the terminals are correct for this application).

I plan to upgrade to a Northstar Group 24F AGM, but I’ll have to modify the battery tray and tie down set up... but the cranking capacity is almost double.

Don’t be too worried about the “start stop” capabilities of the Subaru factory battery... it’s a sub par battery that is better than a normal flooded lead acid, but not as expensive as AGM. It’s undersized for the job, in my opionion. Keeping the battery lightweight and inexpensive keeps manufacturing costs down.

Thank you!

I read somewhere that the X2 (X2Power Premium AGM Battery for 2020 Subaru Forester H4 2.5L 390CCA Car and Truck - SLI35AGMDP at Batteries Plus Bulbs) is the exact same but rebranded Northstar AGM battery, so that looks like an excellent option. I am going to keep it relatively safe and go with the same Group 35 battery as is; I'm not adventurous to delve into group 24 yet

 

@akc5247 I have the X2 Battery running now in my 2001 Subaru Forester. And it's been running great, mind you have some here have criticized, I do not have Start/Stop. But the reason I bought the X2 is because I live TX and the heat here kills any NON-AGM Battery. But I believe AGM batteries are pretty much what everyone is using now for Start/Stop.

 

Thank you @bman400 . If they are in stock, I will be going with the X2. If not, the Optima Redtop.

While searching for Group 35 AGM, I also found these two batteries, which seems awesome from specs (specially the weight). Both are expensive, but curious if anyone on this forum has either of these on their Forester(s)

• Group-35/Q85 Lithium Car Battery
• Group 35 Lithium Iron Phosphate Battery (LiFePO4)

 

Answered in this thread

('19+) - 2021 - Will a 34R battery fit?

I have a 2021/SK Forester. Was wondering if anyone has been successful fitting a 34R battery in place of the stock Q85/35 battery without modification? I was wanting to get an Odyssey Extreme 35 but discovered that they discontinued that battery and only offer that size in an Odyssey...

www.subaruforester.org

 

Late to the discussion but not all vehicles have the guts to fully charge an AGM battery. Our Chevy Tahoe does not.

 

Does the 2019 Forester?

 

I am trying to find out if the 2019+ model year requires a regular flooded or AGM. As mentioned up thread, the 2019 owner's manual states Battery type Q85 (page 492 Electrical system). Yet most retailers' website (in Canada) come up with group 35 AGM, except one comes up with both regular flooded and AGM. None showing Q85. I am more concerned about the correct type over the cost. Which one is the correct type? Or can either be used? The main concern is the AGM requires higher charging voltage that the Forester alternator cannot provide. The other concern is heat (as in the engine bay) shortens the service life of AGM more than regular flooded.

 

I am trying to find out if the 2019+ model year requires a regular flooded or AGM.

I believe the current generation Forester comes with an enhanced flooded battery...

Enhanced Flooded Batteries 101

Enhanced Flooded Batteries (EFB): What are they? How are they different? What are their diagnostic needs? Start-Stop vehicle needs a

www.midtronics.com

...but I would go with an AGM.

 

@max88 , the proper battery for 2019+ models with auto start/stop is an enhanced flooded battery (OEM Q85) or an AGM. The AGM is more readily available and better performing than the EFB, according to everything I’ve read on the topic. Group 35 is the proper size.

All batteries lose life as temperatures increase. I read somewhere (maybe a consumer reports summary) that AGM life is impacted more by heat, but their performance at higher temperatures is better than flooded batteries. I’ve not seen that claim repeated anywhere else in any literature, including conference publications, so I don’t know if CR got it right. Anecdotal evidence from folks in this forum indicates AGM last longer than flooded in the southern states.

AGM’s can handle a higher charge voltage (and therefore higher current), but charging at a slightly lower voltage, like the 14.4 from the Forester, isn’t going to kill the battery. I wish I had a reference publication for that, but at some point I stopped cataloging this stuff, so I’m going from memory.

 

@max88 , the proper battery for 2019+ models with auto start/stop is an enhanced flooded battery (OEM Q85) or an AGM. The AGM is more readily available and better performing than the EFB, according to everything I’ve read on the topic. Group 35 is the proper size.

No horse in that race but thought I'd share that Autozone's top model around here in 35 size (perhaps others that I didn't look for) are EFB with no AGM available.

 

@max88 and @boureesub . AGM battery last 6+ years in TX heat, whereas flooded battery( non AGM) only last 2-3 years. My 2001 got it's first AGM in 2008 and now on it's 3rd AGM this July. Would I ever go back to a non AGM? No way.

I am not sure why so many think heat kills or hurts AGM. When heat kills non AGM. Just look at all the car batteries being replaced here in TX ever summer.

 

I’ll see if I can find the article that made the “AGMs don’t like heat” statement. I think they were misquoting something an Interstate rep said, but you know how it goes once something gets on the internet, it never dies. Like I said, I tried but couldn’t find anything to corroborate the statement, and evidence like yours refutes it.

An old newspaperman friend of mine lamented that corrections and retractions are a bit of an exercise in futility anymore. Once bad information is out there, it’s not going away.

 

@boureesub, now I understand why the owner's manual speicifies Q85 while I keep getting search results in group 35 from forums, yet most retailer websites keep saying group 35 regular flooded does not fit the model year. While group 35 satisfies the physical fitment, it's the EFB/AGM that meets the load requirement. I am glad that I've learnt this before waltzing into my local costco and picking either Kirkland regular flooded or Energizer AGM depending on availability. I have been leaning towards AGM because of mostly short trips but local AGM inventory is limited when I last checked in store.

I turn off auto-stop/start as soon as the engine is running, I may be able to get away with a regular flooded but I am sticking to the OEM requirement.

 

Picked up the Energizer 35 AGM battery from local costco warehouse this evening. It's on a charger now.

Is there any pre-caution before swapping disconnecting the old battery with regard the temporary loss of electric power? I've heard that 2019+ Forester is fine, and will re-learn whatever settings that have been lost along.

 

Picked up the Energizer 35 AGM battery from local costco warehouse this evening.

Costco sells the Interstate AGM here in the US.

 

I use a product very similar to this when changing batteries…

Amazon.com: OBD ll Connector Vehicle Memory Saver Reliable and Easy 9 Volt Battery Powered : Automotive

Amazon.com: OBD ll Connector Vehicle Memory Saver Reliable and Easy 9 Volt Battery Powered : Automotive

www.amazon.com

In fact, I just replaced the battery in my 19 Touring on Wednesday using it, and the car acted as if the battery have never been disconnected.

 

I use a product very similar to this when changing batteries…

Amazon.com: OBD ll Connector Vehicle Memory Saver Reliable and Easy 9 Volt Battery Powered : Automotive

Amazon.com: OBD ll Connector Vehicle Memory Saver Reliable and Easy 9 Volt Battery Powered : Automotive

www.amazon.com

In fact, I just replaced the battery in my 19 Touring on Wednesday using it, and the car acted as if the battery have never been disconnected.

I've been trying to locally source something like that. It takes a while for delivery, especially during the holiday shopping season. And these previously low profit margin items seem to have been squeezed off of local retaillers' product list, now it costs $55CAD on amazon.ca. https://www.amazon.ca/Connector-Battery-Memory-Keeper-Saver/dp/B07KCN69LJ

 

I recently used the exact same memory saver when swapping out my factory battery for an AGM and had the same success as FelineFreddie. You just have to take caution that the disconnected positive cable doesn't ground out on anything.

 

Thanks. That's an important reminder for me that the positive cable is still hot wherever the power source is connected. I have this TrekPow 2500A jump starter that outputs 16.21 volts. Is it too high? When it's used to jump start the car (the actual intended job), the same voltage is applied, so I think (and hope) it's safe.

The new Energizer 35 AGM battery had been on charger for over 36 hours when I disconnected charger 8 hours ago. Right now battery is showing 12.96 volts. Will test again after full 24 hours has passed.

EDIT: tested at 12.93 volts after 24 hours has passed.

 

Locally purchased 9V battery snap and alligator clip jumper leads.

 

Installed new battery.
The 9v dry cell to keep onboard memory alive didn't work as planned. The tiny alligator clip fell off when the whole positive cable was wrapped in plastic bag, so no shorting. The clock was reset back to 01/01/2017, that's the only noticable lost setting. Everything else (radio, trip meters, bluetooth phone/device, maintenance minders) remained intact. Don't know about engine idle, didn't notice anything unusual while driving.

 

Yes, that’s the problem with alligator clips…

 

Lesson learnt. In hindsight, I could have also gotten this ODBII Battery Maintainer Connector to be clipped on inside the car and out of the way. This connector can also be used with my battery charger.

Or I could've put the alligator clips on this that is already installed to the terminals.

 

Anecdotal examples of AGM batteries functioning in heat…

I have had AGM batteries in both my 2005 Mini (very small and compact engine bay) and 2009 Toyota Tacoma (in SC, and it gets pretty hot here…).

Both batteries were installed in 2014 (both are Autozone AGM’s), and still work fine as of today.

I just replaced the Q85 battery in my 2019 Forester Touring with an Optima last week… so far, so good…

 

I was going to upgrade my battery but 35 is sold out everywhere local and I am not keen on buying a battery online in case I need to use the warranty.
So weird thing is my local dealer has an OEM and will install it for a total of 143 which is great price but checking online the OEM battery has been discontinued yet I am not
sure for how long. The tech said it's fresh.

From what I read on here panasonic was the OEM maker and they generally make good stuff.

 

There should be a date code sticker on the battery to let you know the date of manufacture for certain. If not, I'd steer clear.

 

yes there should be a made by date and I will certainly check this but can't beforehand. This dealer has been awesome, can't see them selling me an old junk battery.
I can't find this OEM for sale anywhere online though which is strange, maybe it's just an insider dealer thing.

 

Only AGM battery can be sold online. Regular OEM flooded lead acid cause shipping problems!!!

 

You are correct, I just remembered and that is why you they don't list the battery for sale at online subaru places.