Any reason to not switch to AGM?

Joined
Aug 3, 2010
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366
Location
Michigan
Well my 2016 Accord needed a jump this morning. I'm pretty sure it is the factory battery, so I know I was already on borrowed time.

I am planning to replace it with an AGM 51R - thinking either the DieHard Platinum (Part # 51R-AGM) or a Super Start Platinum (Part # 51RPLT). My options seem somewhat limited presumably due to the size and the reverse terminal position. I'm leaning towards the Super Start due to more reviews and slightly higher CCA.

The reasons why I'm considering an AGM are:
- Longevity - planning to keep the vehicle for a long time still, although to be fair the Honda battery has lasted a very long time.
- The car sits for longer stretches at times / also is sometimes short tripped (~10 minute drives)
- 51R is kind of a small battery - Honda put these smaller batteries in the 4-cylinder models. I'm aware you can buy the parts for a V6 Accord to "upgrade" to the larger battery. I'd rather go this route if it makes sense / AGM would help.
- Personal experience - I've been impressed with how long I've seen AGM batteries last in other family / friends' vehicles.
- Location - I live in Michigan where we have decent temperature swings
- Podcast Recommendation - One of my favorite automotive podcasts, Under the Hood Show, often recommend that people switch to AGM. They do so without referencing any particular brand.

Other than cost, is there any reason I shouldn't get an AGM battery? I know there are small differences in charging rates / expected voltage when comparing Flooded vs. AGM, but surely battery manufacturers have taken this into account?
 
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Stick with flooded it came with one but buy the top of the line series for that size

I‘d recommend buying one with the best warranty for the price. I’m not going to pay $50 more for a battery with the same warranty, for instance. $/weight is also a consideration. Lead costs money and more lead is arguably better.
 
ive heard that too, but I’ve been using AGMs for about 10 years and haven’t had trouble. And, I’ve used AGMs in hondas without issue. Have one in my wife’s crv now. I’m not aware of a way to code for it. Yes, it would be more ideal for a more thorough charge, but i can also tell you that my f150, coded for an AGM, cruises around at 12.4-12.6 volts, well under the desired specs for an AGM, and at most charges around 14.6 for brief moments during braking. as far as battery health, it’s pretty hard on them. (Changes with temp by a couple tenths of a volt on either end.)

@cutlassvillager - can you fit a gp 35 in there instead of the 51r? The 51r is a small battery. Our CRV accepted a group 35 with only minor tweaks.
 
Nope. A switch to AGM requires coding in the ECM. Techs usually do this for free with purchase.

Putting an AGM battery in a car coded for flooded will disappoint.

That’s interesting. I’ve never heard of an ECM capable of being programmed for an AGM over a stock flooded cell. Why would an OEM put the money into this option?
 
ive heard that too, but I’ve been using AGMs for about 10 years and haven’t had trouble. And, I’ve used AGMs in hondas without issue. Have one in my wife’s crv now. I’m not aware of a way to code for it. Yes, it would be more ideal for a more thorough charge, but i can also tell you that my f150, coded for an AGM, cruises around at 12.4-12.6 volts, well under the desired specs for an AGM, and at most charges around 14.6 for brief moments during braking. as far as battery health, it’s pretty hard on them. (Changes with temp by a couple tenths of a volt on either end.)

@cutlassvillager - can you fit a gp 35 in there instead of the 51r? The 51r is a small battery. Our CRV accepted a group 35 with only minor tweaks.
There is no way that your vehicle runs for any period of time at 12.4-12.6VDC. 12.6VDC isn’t full-charge voltage. The only time I see this is when driving after the battery has been on a charger and fully charged. Otherwise, the voltage should be 14+ VDC or at least in the 13s for a proper float voltage.
 
I would upgrade to a larger battery while your at it. Simple to do, lots of YouTube videos to show the few parts you’ll need.
I upgraded to a 24F, big difference in cold temp cranking speed, and lots of reserve compared to a 51R.
 
How? If my alternator was designed for a flooded LA battery and puts out 14.3VDC and the AGM battery wants more than that, then the battery will never charge fully.
My cell phone can charge at 100% or to preserve battery life 85%. Maybe same thing?
 
Odyssey has a lot of info on how to charge AGM batteries. Unless your car came with one, it will ruin it because of the incorrect charging pattern.
Odyssey has a lot of info on how to charge AGM batteries. Unless your car came with one, it will ruin it because of the incorrect charging pattern.
Just replaced my agm bought in 6/2015 , it didn't get that memo. Still cranked fine but cca was getting low according to the tester.
2012 Toyota Sienna oem battery was wet cell.
 
I'm biased since I've done the switch already on my 2015 Accord Sport, but save the money you'll spend on an AGM unit and just install a larger battery. The 24F and 35 are actually cheaper and more common.


A 24F EverStart Maxx is overkill for a 4cyl Accord so it's not taxed in the least. I'm hoping to get 8-10 years out of it.
 
li-ion loves 40%, hates 0% and doesn‘t like 100% state of charge (SoC). That why 20-80% is the best compromise for capacity and longevity.

Lead-acid loves 100% SoC. Every second below 100% SoC degrades the battery to some extent.
If it lasts as long as my last one that's fine with me.
 
If it lasts as long as my last one that's fine with me.

Do what works for you. I just posted to say that your average charging system will not maintain an AGM battery fully charged.

For me, I have an expensive flooded battery that is always showing a low SoC, even thought to he charging system is good, there is no known excessive parasitic drain, and I use a smart charger often. It’s probably just a battery issue, but it keeps starting without issue, so it’s impossible to justify replacing it. Even at around 12VDC it starts the engine just fine, but the habitual lower SoC will eventually do it in.
 
That’s interesting. I’ve never heard of an ECM capable of being programmed for an AGM over a stock flooded cell. Why would an OEM put the money into this option?
Different charging voltages, charging routines and state-of-charge calibration. Manufacturers use different batteries depending on region, climate and...market I assume.

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