AGM batteries - are they better?

[DryCamper11]

Upgrade to an AGM battery. You can safely mount them inside, and upside down, and they will out-perform any flooded battery you ever owned!

Here's a quote from another thread. It's typical of others I've seen. I wonder if anyone here can convince me it's correct. Clearly the AGM has some advantages. Two are seen in that quote - inside and upside down. If you need to mount upside down and can't ventilate, sure, that's an advantage, but I don't need those advantages and don't want to pay extra for something I don't need.

We're left with the rapid charge rate they are reputed to permit. I would love to run my 80A charger at 80A continuously until I reach 100% SOC. Right now my 460AH FLA batteries recharge at 80A from 50% SOC for about 3 hours (some fluctuation in current - slow climb from below 80 to above 80 during the first hour as they warm up then down to 70+ at the third hour), then begin to taper more rapidly during the last hour as the battery voltage approaches the charger voltage.

Does anyone have charge curves for AGM showing the performance (preferably with an 80A charger)? I'd particularly like to see the tail end of the charge cycle. How do AGMs perform? Is it significantly better than FLA batteries? Do AGMs taper the charge rate the way FLAs do, or is the entire advantage in the fact that I could run a bigger charger (100+ A) for my 460AH battery bank?

Are there other advantages that AGMs offer?

[Almot]

full_mosey wrote:
Folks, look at this list. Flooded, AGM or Gel...Which is Best?, it is from Deka East Penn, a quality mfgr. They mfgr all three types.

Good summary. Easier to read than some long threads on forums :)... Though I question at least 3 of their ratings.

1) Recovery after discharge below 50%, AGM is better than FLA. My UPG AGM warns not to discharge below 60%. Maybe Deka AGM is radically different and SOC below 50 doesn't affect it instantly (didn't try to do this to my AGM, though I doubt it will affect it instantly), but AGM being "better"?

2) Shelf life, Starting FLA = AGM. Since when shelf life of any FLA is same good as AGM?

3) Low initial cost, Deep Cycle FLA = AGM. I don't know, maybe this is true for Deka, their FLA are not very common, but this is definitely not true for other brands. AGM technology is getting cheaper so the gap narrows, and bargains can be found if you shop around, but generally, $/AH AGM is more expensive and this makes sense because technology is more complicated.

[full_mosey]

Folks, look at this list. Flooded, AGM or Gel...Which is Best?, it is from Deka East Penn, a quality mfgr. They mfgr all three types. Wouldn't this list be even handed?

HTH;
John

[mena661]

PN, there's cons just none of the AGM owners want to hear them. When i was researching batteries, I had pros and cons for FLA vs AGM and chose FLA based on that and input from forum members.

[pnichols]

Mena,

I'm not aware of any cons to use of AGM batteries in an RV at this point in their development, except cost. If the battery discussions would concentrate ONLY on cost of ownership per electrical energy delivered over the life of the battery - then some of these discussions would make factual sense.

Without regards to cost ... the discussions could get real interesting. You and I both know the state-of-the-art "best" battery for RV use right now ... that battery type name starts with "l" and ends with "n", with these letters in between ... "ithium io".

Here's a typical link to them that you are probably getting tired of me posting:

http://www.lithiumion-batteries.com/lithium-rv-deep-cycle.php

[mena661]

Thanks for the clarification Wanye. No ones dumping on AGMs. Facts are facts. I personally despise participating in AGM threads because their owners take ANY info presented as a personal attack. I've even been accused of being a cheapskate cause I don't own AGMs nevermind that I probably have one of the most expensive battery banks on the forum. Just happens I chose FLA. Each battery type has pros and cons and what is best is up to the individual.

[Wayne_Dohnal]

You've got 12 house batteries in your rig? That's impressive! I wonder why I didn't know that already. I did use the word "MOST" in my post. Maybe I didn't. Let me go back and check.

I apologize, not meaning to mislead by omission of the location. The 12 AGMs are in the home PV system. With that large a bank the lower self discharge rate is a key component of maximizing production and battery lifetime. Packed into the case they're in, accessing the filler caps is difficult. I've been feeling like this is a "dump on AGMs" thread and am playing a little bit of defense. IMO it's not a clear good-bad situation and AGMs are the better overall choice in some applications and usage models, including some RV situations. Outback Power, I assume agrees. They recently launched a new line of batteries and they are all AGMs.

[pnichols]

The two 7-year-old 100 amp hour 12 volt AGM batteries in our motorhome are Interstate DCM0100L wheelchair batteries ... which are no longer carried in the Interstate line.

I'll probably replace them with a couple of these superior replacement (120 amp hours, each) AGM batteries, since they're about the same size and have the same recommended 13.5V-13.7V float voltage requirement ... and hence will not require me to get rid of the RV's stock Parallax 7345 ~13.8V fixed voltage converter that has taken care of my current AGM batteries so well over the years ... the 20% increase in amp hour capacity (from 200AH to 240AH) will be a nice bonus, too:

http://www.amazon.com/VMAXMB137-Replacement-Interstate-DCM0100L-Wheelchair/dp/B00F595UYW

BTW, IMHO it would probably be best to think about dispensing with the no-longer-true comments about AGM batteries being of a lot less capacity than FLA batteries of about the same weight.

[harold1946]

Johnson Controls recently made a huge investment, 6+ million, to their facility and added about 200 employees because of the increased demand for VLRA batteries.
Three of our local golf courses have switched to AGMs. BMW and Harley Davidson have AGMs as standard equipment.

I have personal knowledge of 140 class A motorhomes that have two AGMs as original equipment. Each unit has two Deka 8D 12 volt batteries.
Not everyone on RV.NET has AGMs. Likewise not everyone that has AGMs is a member of RV.NET.

[mena661]

Wayne Dohnal wrote:
I've got an even dozen. Who has the other 28?

You've got 12 house batteries in your rig? That's impressive! I wonder why I didn't know that already. I did use the word "MOST" in my post. Maybe I didn't. Let me go back and check.

Most people here have 1 or 2 batteries tops.

Yep, I used the word "most". That would exclude you (and me for that matter). If you peruse the forums, you'll find that MOST people have 1 to 2 batteries tops. Large banks of ANY battery are NOT the norm here let alone with RV owners in general. You and I are WAY outside the norm which was the whole intent of my post. To show that the average RVer with AGM batteries will NOT put a scratch on AGM battery sales enough to lower pricing. When the golf courses start using AGM's, then you'll see drastic, across the board, price cuts on AGMs.

[crosscheck]

bcbigfoot wrote:
Now that I have 2 AGMs I have time to look up the meaning of words like "esoteric".

Crosscheck just up the valley from you in Armstrong, lots of rain over here eh!

Hey bcbigfoot,

Would you believe it, in 1 hour, Mrs. Crosscheck is dragging me up to the Star to go skiing. It,s snowing buckets up there.

Dave

[bcbigfoot]

Now that I have 2 AGMs I have time to look up the meaning of words like "esoteric".

Crosscheck just up the valley from you in Armstrong, lots of rain over here eh!

[crosscheck]

I never used to have time to respond to RV.Net forums when my batteries were the flooded types as I was spending a lot of time maintaining them, but now with only the yearly group hug with my AGM,s, my life has been freed up to do more esoteric things.

Put me down for 4.

Dave

[big_buford]

9 and counting I like um:)

[jmckelvy]

Wayne Dohnal wrote:

My guess is maybe 20 people here have AGM's, that's 40 batteries tops (extreme WAG but I don't think I'm too far off).

I've got an even dozen. Who has the other 28?

I have 4. Two Duralast Grp 65 starting batteries in the truck and 2 Grp 27 12V Lifelines in the camper(6 years old and still working great).

[harold1946]

Wayne Dohnal wrote:

My guess is maybe 20 people here have AGM's, that's 40 batteries tops (extreme WAG but I don't think I'm too far off).

I've got an even dozen. Who has the other 28?

I have three of them, but they are 12 volt 8D's. Does that count for three or six? :@