Any reason NOT to get an AGM battery?

[Craig in Canada]

Related to http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2147446#Post2147446

I'm seriously considering an AGM replacement battery in my BMW. I've read a lot of (sometimes conflicting) information on charging restrictions and whatnot for AGM batteries. My system voltage is 13.8-14.0VDC any time I've ever measured. Generally if I am plug in charging I'm using a float/maintainer which hovers in the low to mid 13s.

Other than a price delta of $60 in my market ($188 vs. $247 for group 49), is there a reason NOT to get AGM? I'm not sure the reported benefits are worth the $60 either.

Thanks,

 

[yeti]

craig -- i read some of the other thread, and i found it amusing.i don't understand why some do various testing on a battery, and agonize over it's purchase, when they will buy one anyway.
my nearly 5 yr. old battery died recently, due to dome lights left on, by accident.my neighbor drove me to canadian tire, where i bought their top end eliminator for about $115. 3/9 yr.warranty, and about 900 CCA. i buy the highest CCA battery that will fit in my battery tray.after a total time of 20- 25 minutes, we had the new one installed, and were having a brandy.
eliminator, or w-mart's everstart(?) for a 3/9 yr. warranty and the highest CCA that will fit in your tray -- that's it - done.doesn't matter what brand name you buy. you'll get the odd bad one from any brand. that's fact.
THAT is why i don't spend a lot of time on what is essentially a mickey mouse decision.maybe, it's because i'm lazy. i mean no disrespect -- but you 'gotta be honest -- a battery buying decision is not a big deal -- we're not talking about cold fusion here.it's a plastic box with lead plates, and acid.
at any rate, good luck, and have a good night.

 

[wrcsixeight]

Look up the individual charging characteristics of your proposed battery as they all vary slightly. If you are reading in forums, some people interchange the term Gel batteries with AGM, when they are two different batteries with much different charging requirements.

If a flooded battery cost me that much, and an AGM only that much more, I'd get the AGM.

Where I am AGMs are double and then some.

I've never seen a BMW battery tray or mounting method, but I would not be afraid to buy something a little different and make it fit/mount tightly, if there was a cost savings or I could get a superior battery for the same money.

 

[meep]

aside from cost, no. I dabbled in solar/wind power for several years and got up close and personal with AGM batteries. They have less self-discharge. they are sealed. they withstand vibration better. They suffer from fewer modes of failure (shorted cels eliminated physically).

Solar-wind systems often favor non-agm, as flooded cels are more serviceable, but in your case it could be an advantage.

they do not like being overcharged, but your voltages are fine.

for critical applications where they are well-cared for, especially if they are shielded from heat (does the bimmer keep it in the trunk?) I think it'd be worth it. you *might* get slightly longer life out of it, to make the cost worthwhile.

What I'd REALLY pay attention to, however, is the capacity in amp-hours. they often can squeeze a bit more into the AGMs, which means, if all other factors are equal, it is less strained in a given application. That will lead to longer payback than anything else. Conversely, if the AH rating is lower, it would NOT be worth it, in my book.

M

 

[brianl703]

Originally Posted By: meep
They suffer from fewer modes of failure (shorted cels eliminated physically).


I wish. The ones in UPS systems routinely suffer from shorted cells, with the attendant venting and physical distortion of the plastic case. This problem is apparently made worse by higher operating temperatures.

 

[Craig in Canada]

@yeti:

Well, the matter isn't so simple if the acid doesn't stay inside the battery - a problem with the last two Interstates I've owned purchased from different locations years apart. Nor is it so simple if I were to get an AGM battery (to guarantee no acid damage) only to have it prematurely ruined by my charging system because of some factor I am ignorant of. I also read somewhere that swapping an AGM battery into an application could cause alternator overheating due to the AGM battery sinking far more current than the original flooded battery due to lower internal resistance when re-charging after starting. Just sayin'.

CCA, price, discounts and warranty don't matter much if the battery causes damage to the vehicle it is installed in. And, frankly, I would rather never have to use a battery warranty than have a great warranty I need to use every 18 months. Mid-90s era Canadian Tire Eliminators did that to me - I was in for a pro-rated replacement every 18-24 months because a cell would short and it wouldn't start (10.xV terminal voltage).

Why did I agonize over testing/bench charging the battery? Because the problem could have been a parasitic drain by the car while parked. I read posts every day where people throw parts at a problem without any testing and they buy a new battery only to have it go dead on them again - money wasted.

 

[Craig in Canada]

Originally Posted By: meep

What I'd REALLY pay attention to, however, is the capacity in amp-hours. they often can squeeze a bit more into the AGMs, which means, if all other factors are equal, it is less strained in a given application. That will lead to longer payback than anything else. Conversely, if the AH rating is lower, it would NOT be worth it, in my book.

M


I believe the AGM group 49 has higher CCA and lower Ah than the flooded. Something like 1000CCA AGM vs. 850 or 900CCA and 95Ah AGM vs. 110Ah. So, AGM gives less reserve but more cranking amps.

 

[rslifkin]

AGMs aren't much different than flooded as far as charging, except for the lower overcharge tolerance. An alternator feeding it should be no problem.

 

[HTSS_TR]

Originally Posted By: Craig in Canada

Other than a price delta of $60 in my market ($188 vs. $247 for group 49), is there a reason NOT to get AGM? I'm not sure the reported benefits are worth the $60 either.

Thanks,

Did you check the price of Everstart Maxx at your local Walmart ? It's only $82 at my local WM, it may be a little in Canada but not more than double.

I would go with AGM for 30% more than flood battery, but in my area the cost of AGM is similar to your price of $247 which is about 3 times WM price.

 

[Audi Junkie]

People are moving away from them.

 

[Eddie]

I see no advantage to them in this application. I just go to WalMart and get the top-of-the-line and that's it.

 

[yeti]

craig -- if you had bad luck in the past with CT batteries, then i can see you being gunshy.several people that i know,in the last 20 or so years, had no issue with them, or WM units.i guess luck is a factor.you'll get good and bad, regardless of brand.
testing and brand comparison are out of the question with me --as stated, because i'm lazy.highest CCA that will fit my tray, and a 3/9 yr.warranty are my priorities.
at any rate, take care, and have a good night.

 

[CBR.worm]

Does your BMW require new batteries to be registered? If so you may have better luck with the AGM as the charging system will be tuned for the new battery.

 

[wrcsixeight]

Originally Posted By: Craig in Canada
I also read somewhere that swapping an AGM battery into an application could cause alternator overheating due to the AGM battery sinking far more current than the original flooded battery due to lower internal resistance when re-charging after starting.


This might apply in a RV type application where one cycles a bank of AGM batteries to 50% or less. Some AGM batteries can accept huge currents, like 3 times the amp hour capacity of the battery and could conceivably overwhelm the alternator, but this is limited in starting battery applications. Also the stock charging circuit wiring is going to limit what can be passed back to the battery, Kind of like trying to drink through a cocktail straw.

Do not worry about this in your application.

 

[Craig in Canada]

Originally Posted By: yeti
craig -- if you had bad luck in the past with CT batteries, then i can see you being gunshy.several people that i know,in the last 20 or so years, had no issue with them, or WM units.i guess luck is a factor.you'll get good and bad, regardless of brand.
testing and brand comparison are out of the question with me --as stated, because i'm lazy.highest CCA that will fit my tray, and a 3/9 yr.warranty are my priorities.
at any rate, take care, and have a good night.


It was the 90s when I had CanTire batteries give up the ghost with a cell short. They certainly could have changed vendors several times by now. It's my current experience with JCI/Interstate that has me gunshy, since they have come from the factory overfilled and don't seem to have much in the way of internal baffling or good seals on the caps (on remote vented models at least) to keep from expelling electrolyte. With Interstate it wasn't "one bad egg", it was two for two, two years apart, bought from dealers 50 miles apart. Electrically they seemed very good.

 

[Craig in Canada]

Originally Posted By: CBR.worm
Does your BMW require new batteries to be registered? If so you may have better luck with the AGM as the charging system will be tuned for the new battery.


No, I've read about that but mine's too old for that

 

[Craig in Canada]

Originally Posted By: HTSS_TR

Did you check the price of Everstart Maxx at your local Walmart ? It's only $82 at my local WM, it may be a little in Canada but not more than double.

I would go with AGM for 30% more than flood battery, but in my area the cost of AGM is similar to your price of $247 which is about 3 times WM price.


I went to my local Walmart last night to check this out. They did not have much in the way of "Everstart Max" other than some deep cycle, marine and possibly powersports batteries. Most of the automotive line was Energizer Max by Johnson Controls.

They had a group 49 there for $117, a significant savings over what I've found so far for Deka. A couple of things, though:

1/ They only had one battery and it had an Oct/2009 date sticker on it - no thanks

2/ I didn't see any venting apparatus or kits. There wasn't a blue smock to be found to save my life so I couldn't ask a knowledgeable person about whether they give you some kind of a plug and elbow kit over the counter when you make the purchase

3/ The rating printed on the battery was 750CCA. The Deka options I'm looking at are all 900CCA and higher. Depending on which spec sheet I look at, one of them even says 1000CCA in my size. I'm not sure that I want to leave ~200CCA sitting on the table.

4/ Based on my knowledge of how my cables hook up, I wasn't positive that the shape of the top of the battery would allow my positive terminal to hook up properly. This would really surprise me, since this should be a regulated standard of the group 49 design. I could be wrong on this, but it looked off to me.

I will say that the cell cap design looked better than on my Interstate MTP-93. Instead of a snap in cover which covers three cell at a time it had a threaded cap per cell which you remove with a coin. I didn't remove any to see if there were O-rings used but I think it would seal better.

 

[meep]

Originally Posted By: brianl703
Originally Posted By: meep
They suffer from fewer modes of failure (shorted cels eliminated physically).


I wish. The ones in UPS systems routinely suffer from shorted cells, with the attendant venting and physical distortion of the plastic case. This problem is apparently made worse by higher operating temperatures.


I've seen UPS's pop larger batteries in a glorious and "glad-they're-in-a-metal-case" fashion. I think because UPS can do a 20 minute full drain on any battery at top-current until they're drained, it's a unique circumstance. I'd also be curious if they are really AGM.... I've had some that were indeed, and some replacements that said they were but were not. And it's a crâp shoot trying to accurately know what you are buying. Most consumer UPS replacement batts I've seen are just gel cells.

HEAT-- agree- this is a big factor. I do believe (opinion) that AGM's don't handle heat as well. If this is a not a trunk-located battery (I asked, no answer), then flooded could be more resilient, off-setting the cost of AGM.

With someone above mentioning higher CCA but lower AH, it tells me that every start will be quick and snappy, but at a greater depth of cycle. Deeper cycles over time mean quicker aging.

I'm leaning towards the "energizer" (Johnson) battery. I had a JCI last 7 years in a subaru, including a couple all-night-lights-on episodes. It still worked when I replaced it-- was just getting sluggish.

M

 

[Craig in Canada]

Originally Posted By: meep

HEAT-- agree- this is a big factor. I do believe (opinion) that AGM's don't handle heat as well. If this is a not a trunk-located battery (I asked, no answer), then flooded could be more resilient, off-setting the cost of AGM.


Sorry - my application is indeed trunk mounted.

Quote:

I'm leaning towards the "energizer" (Johnson) battery. I had a JCI last 7 years in a subaru, including a couple all-night-lights-on episodes. It still worked when I replaced it-- was just getting sluggish.

M


I'm leaning in the direction of the flooded Deka. If this batt has a service life of 5 years or more and doesn't leak, I should be happy. In the meantime I'll save my $60 for other things that need fixing. I *do* like that the Deka has significantly more CCA than the Walmart JCI and that the Deka line is an "OE exact fit". I'll be nice to get back to a battery with absolutely no kludgeyness in terms of venting, cabling, handles or mounting as compared to the Interstate.

 

[meep]

Posts can be reversed within the same group.... think there is an "r" designation.

Venting is important--- not that you see acid venting but there are traces of it if the battery is in a high-overcharge situation. I don't have much experience with deka, but I see them in a lot of smaller sealed LeadAcid batts. Sounds like a safe bet to me.

I once shoe-horned a JCI battery, (civic sized) into a trunk-mount miata. miatas used expensive, tiny, AGM batteries from the factory. People hated them because of their limited capacity. use of the civic-type batt meant I couldn't vent to a tube. Didn't have the car long enough to know if it had problems. we did have an 84 vanagon with an inside battery, no venting mechanism. never had any problems with it. don't think it was sealed either.... screw caps. so, who knows. But if the car/trunk is nice, deka sounds good to me!