PSA: Don't use AGMs Batts Underhood

[TeCKis300]

Community learning is catching up. The messaging is now building steam and becoming more consistent.

Public service announcement - AGM batteries should not be installed underhood in the hot engine bay. What's best for a starting battery is what the system was designed for, a high quality flooded lead acid battery.

@4:29


@0:47


For years, people have been buying into advertisements from battery manufacturers themselves, promoting AGM as a general upgrade for Flooded Lead Acid batts. They are indeed great. Yet application is important as they do not tolerate underhood heat well and will have a prematurely shortened life when used as such. Charging profile is also important, with AGMs best maintained by a type selectable DC-DC charger.

 

[KLF]

So... You want me to take my perfectly functioning batteries out (cost ~$400), throw them away, and buy something else. Right. I'll get right on that.

 

[TeCKis300]

So... You want me to take my perfectly functioning batteries out (cost ~$400), throw them away, and buy something else. Right. I'll get right on that.

Don't worry about what I want. Your perfectly working batteries will do the asking for you.

I've played this AGM game multiple times over 10 years ago. Fortunately they were always warrantied.

I don't care for that game again, and am sharing so others don't have to either.

 

[bryson]

I've always seen the same or better life out of my under-hood mounted (and properly charged) AGM batteries than a FLA. Not saying one is better than the other in that environment, but I don't plan on changing my ways or my batteries.

I have no idea if this is/was the issue you experienced with your AGM batteries @TeCKis300 , but most AGM issues I have seen are due to improper (too low) charging voltage. Charging voltage becomes an even bigger concern/problem the further away from the alternator you mount your battery (i.e. not under the hood).

 

[cru1s3r]

Your timing is perfect - thanks. My battery is > 3 years old and, due to temperature extremes, is starting to show degradation. I'd just started to research process, and I was wondering if AGM was now the way to go. Guess it's time for a trip to Costco for a new flooded battery.

 

[KLF]

Until a reputable battery MANUFACTURER confirms this position, this is all opinion. No facts back it up, at least i don't see any. One person's experience doesn't make it fact.

I'll agree that AGM batteries do take more care. Mine get a full optimization charge every weekend, but I've made it really easy, takes only a few seconds to hook up to shore power. I believe my Miata will be needing a new battery soon, but i won't be going AGM, don't see the benefit.

This is no PSA, thread title needs to be changed. It degrades the other threads that provide genuine info, such as the radiator thread.

 

[RBA]

interesting, some manufacturers use AGM as OEM batteries in the engine bay.

 

[Moby]

So what are good options for non AMG? I've always run yellow tops, duals in my FJ-62 and single in my GX, because I don't daily drive these trucks. But I have been thinking of duals for the 200 and while I believe in matching both batteries (brand/type/age) just buying on extra to work with the factory battery would be nice.

 

[TeCKis300]

I have no idea if this is/was the issue you experienced with your AGM batteries @TeCKis300 , but most AGM issues I have seen are due to improper (too low) charging voltage. Charging voltage becomes an even bigger concern/problem the further away from the alternator you mount your battery (i.e. not under the hood).

Agreed that this can be part of the issue if mounted remotely. Partly ties into the fact that the stock alternator regulator is not setup for the AGM type and remote mounting.

@RBA Yes, OEMs use AGMs. It is designed in as part of the overall system with consideration to heat and charging. When found underhood, it's behind a partition to isolate them from the engine heat. The regulator is also setup for AGM charging profile. Who wants to be plugging in their car battery regularly anyways. A sure sign that the battery system is not designed right.

To the question about my experience. This was my engine swapped IS300 - supra twin turbo 2JZ-GTE and getrag v161 6-speed that I did every bit of. See that battery at the upper left? That's a best of breed AGM - Odyssey Extreme full metal jacket. Designed for high heat. They never lasted more than 2-3 seasons (these were smaller so the degradation was more obvious). Manufacturer replaced first. Replaced second contingent on me buying their branded charger, and is when I decided plugging in constantly was BS. 3rd time, yeah, no thank you.

Australia has blistering temps in places so perhaps that's why their learning faster and where these vids in the first post are coming from. Don't take my word for it. It's going to be those low speed off-roading long crawling days that really heat up the battery with little airflow. Or in my previous case, long track sessions that get everything hot and heat soaked.

 

[TeCKis300]

Until a reputable battery MANUFACTURER confirms this position, this is all opinion. No facts back it up, at least i don't see any. One person's experience doesn't make it fact.

I'll agree that AGM batteries do take more care. Mine get a full optimization charge every weekend, but I've made it really easy, takes only a few seconds to hook up to shore power. I believe my Miata will be needing a new battery soon, but i won't be going AGM, don't see the benefit.

This is no PSA, thread title needs to be changed. It degrades the other threads that provide genuine info, such as the radiator thread.

Hey, I get it. No one wants to spend tons of money only to learn after it wasn't as great. Manufacturers are only interested in one thing...sell. They'll show you nicely painted rainbows and tell you everything you want to hear.

Like I said, I've played this game and had my fair share of experiences. Aftermarket stuff especially. Like the LRA subtank that everyone here said was so great and dropped right in. I temper my expectations and am far more critical. I'll share the good bad and ugly, even if it's thousands that I've spent. It's only in that way that the community will progress. Just like the now revised LRA subtank which does actually drop in.

 

[Fisher23]

Hey look someone posted some youtube video .. they must be an expert ... ... I think not.

AGM is way better offroad or in any situation where you will be getting a lot of vibration. If you are just city driving then lead acid is fine. Look at any score or mdr truck.

Washboard roads kill lead acid batteries. I have first hand experience with that.

If the battery is in the engine bay manufactures usually mount it up front, because it is cooler there.

 

[gaijin]

Don't take my word for it.

OK.

 

[FrazzledHunter]

I used an Odyssey 35-PC1400 AGM for my 2nd battery even after I read this thread on the matter of heat.
I did measure some temperatures on a 70 F day the fan kicked off air at about 120F which blows right by the side of the battery.
I'm not sure how bad that is.

In the end the issue was size & cost. I couldn't find a deep cycle flooded lead acid in a amp-hour size I liked that would fit and I didn't want to pay for a lithium. I'll see how things go. Thanks for the original post.

 

[40Man]

Sorry, but my experience and science disagrees with this. First off, ALL car batteries, whether traditional flooded lead or AGM do not like heat. Studies show that a traditional lead acid battery service life cuts in half for every 18 degrees above 77 degrees F. So a six year battery that lives in 100 degrees will have its life cut in half. This is due to accelerated chemical activity in the battery due to absorbing more heat.

Some lead AGMs are similar as both have galvanic corrosion which increases in high heat, reducing battery life (think of the old yellow and red tops). However, the current advanced AGM manufacturers took galvanic corrosion into account in the design of thin plate pure lead AGM batteries (like my Northstar AGM and the Odyssey), which DO NOT have galvanic corrosion, and have a 10-12+ life because of these manufacturing changes. And, they have a wider range of operating temps, for better performance in heat and cold.

On top of that many have a metal jacket insulating from heat.

The biggest killer of AGMs is improper charging. Overcharging, or too low voltage charging.

I have a specific AGM charger and top off my cars regularly. Never had a problem with any of them.

Now for the cost of an AGM, it may not be worth it to most drivers. As you can replace a standard lead for $99. For me, the peace of mind of likely not having a catastrophic failure in the backcountry is worth it (even if I have a backup along).

Bottom line, all batteries could benefit from being installed remotely away from heat, but current AGMs are designed to handle heat BETTER than a standard flooded lead acid battery.

 

[TeCKis300]

The biggest killer of AGMs is improper charging. Overcharging, or too low voltage charging.

....

Bottom line, all batteries could benefit from being installed remotely away from heat, but current AGMs are designed to handle heat BETTER than a standard flooded lead acid battery.

Don't disagree. I've quoted two statements of yours.

If you consider the vehicle as an overall system, the charge profiles are not setup for AGMs. Sure, if you have it as an aux battery, you could have a DC-DC charger with the proper AGM charge profile and temperature compensation.

As a starter battery, tendered by the alternator regulator with profile for flooded lead acid, no AGM is going to last as long as it should. Add in a voltage diode hack...it'll die earlier still.

I invite you to solve the system problem. AGMs are great components.

 

[40Man]

Don't disagree. I've quoted two statements of yours.

If you consider the vehicle as an overall system, the charge profiles are not setup for AGMs. Sure, if you have it as an aux battery, you could have a DC-DC charger with the proper AGM charge profile and temperature compensation.

As a starter battery, tendered by the alternator regulator with profile for flooded lead acid, no AGM is going to last as long as it should. Add in a voltage diode hack...it'll die earlier still.

I invite you to solve the system problem. AGMs are great components.

I am on year 5 of mine with my oldest one with no issues. I regularly check my alternator voltage and it is usually at the minimum 14.1v my manufacturer recommends (less in hot summer). My battet voltage mains in a acceptable range, and I tend to shuffle my rigs to my AGM charger every 3 weeks for a top off. If you don't charge these regularly, it may cause issues. I have a quick connect on all my rigs, so it is simple to do.

AGM are not for everyone. My point is, your title and majority of your original post are inaccurate based on the composition of modern advanced AGMs.

 

[TeCKis300]

I am on year 5 of mine with my oldest one with no issues. I regularly check my alternator voltage and it is usually at the minimum 14.1v my manufacturer recommends (less in hot summer). My battet voltage mains in a acceptable range, and I tend to shuffle my rigs to my AGM charger every 3 weeks for a top off. If you don't charge these regularly, it may cause issues. I have a quick connect on all my rigs, so it is simple to do.

AGM are not for everyone. My point is, your title and majority of your original post are inaccurate based on the composition of modern advanced AGMs.

It's your prerogative and you can interpret whatever you like out of it. 5 years for a battery is no achievement when stock batteries easily go that and more.

I never have to put mine on a float charger for maintenance. That should be a clue that it's not the right component for the job, and IMO is not a desirable feature.

You may want to note that you're in a mild temperature climate being in Washington. Those of us in arid desert climates have different experiences. Which is why Australia is ahead on this and some of the leading videos on the topic come from them as they have much hotter average temperatures. I stand by my recommendation. There is enough history on these boards that people are starting to see some of this firsthand.

 

[JohnPW]

I have used AGM batteries (Odyssey) in my trucks in south Florida after using them for many years in boats. The vibration resistance and lack of maintenance (other than proper charging) make them a great fit for marine use, where I have 3 to 4 AGM’s for starting, deep cucle and trolling motor use. I get @ 5 or 6 years out of them in spite of deep cycle use, which is significantly longer than flooded batteries last in the boat.

However, in the truck they have not lasted any longer than a flooded battery. They haven’t been any better, or any worse than FLA batteries. I can see where the vibration resistance could be an advantage off road, but for me they haven’t been worth the extra $ in my cars and trucks. So I have gone back to flooded batteries in my cars.

 

[LexCruiser08]

Yeah I definitely think this is more of an opinion vs fact based evidence. Optima has been making AGM batteries for years without issues with under hood usage. I wouldn’t hesitate to use one.

 

[renago]

I drop in my personal experience , and you come to the conclusion yourself .
I have 2 AGM Optima 75 ah in my motor bay .
the truck has seen extensively trips for aprox 10 years in the desert of Sahara during august , rather hot period .
the 2 batteries are there to start the motor and fridge ,plus some lights .
charging system is by standard alternator only .
after 14 years of service they are still running , not to the top , but decently well .
say 80 % aprox .
will hold my fridge for 1 full day in summer without charging , second day will be more critical .
starting is never a problem .

shall I move the batteries or shall I keep them ?

just my 14 cents in 14 years