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Battery group size? [Q85 or 35] - SOLVED!

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#22 ·
Thanks for your posts.
That's what I have been wondering about, which, as explained by bman400, is OK. Given that many have posted using AGM battery, the 2019 model year should be able to handle AGM's higher voltage requirement.

Kevin said:
I too have read that but many people are using them in the engine bay so it must be OK :unsure:
Click to expand...
bman400 said:
AGM battery in trunk because they do not have fluid to leak out. Try that with a non-AGM battery!
Heat kills regular flooded lead acid battery because heat causes the liquid to evaporate and exposing the plates. The AGM does not have this flooded concept and therefore no fluid to evaporate. Therefore they last longer in high heat condition.

Here in TX, a non-AGM battery dies in 2-3 years. While the AGM battery last 6+years.
Click to expand...
 
#23 · (Edited)
@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.
 
#24 ·
@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.
 
#25 ·
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.
 
#26 ·
boureesub said:
@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.
Click to expand...
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.
 
#27 ·
@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.
 
#28 ·
max88 said:
I am trying to find out if the 2019+ model year requires a regular flooded or AGM.
Click to expand...
I believe the current generation Forester comes with an enhanced flooded battery...
www.midtronics.com

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 www.midtronics.com
...but I would go with an AGM.
 
#30 ·
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.
 
#31 ·
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#32 ·
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.
 
#33 · (Edited)
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.
 
#35 ·
ForesterBill said:
Costco sells the Interstate AGM here in the US.
Click to expand...
Costco in Canada, at least in my local area and likely across the country, sells the Kirkland brand standard flooded that is only available in the warehouse, and not available for shipping due to hazardous materal classification. It's website does not even have product information for standard flooded batteries. The Energizer brand AGM is available in the warehouse and online for shipping. Shipping costs $30CAD extra for my group size 35.
 
#36 ·
FelineFreddie said:
I use a product very similar to this when changing batteries…


www.amazon.com

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.
Click to expand...
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. :rolleyes: https://www.amazon.ca/Connector-Battery-Memory-Keeper-Saver/dp/B07KCN69LJ
 
#38 ·
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.
 
#40 ·
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…
 
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