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MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 11/07/20 07:27pm Link  |  Quote  |  Print  |  Notify Moderator

CAN NOT DRY OUT AGM UNLESS THEY CONSTANTLY VENT but you can damage the plates.

Gdetrailer

PA

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Posted: 11/07/20 08:59pm Link  |  Quote  |  Print  |  Notify Moderator

MEXICOWANDERER wrote:

CAN NOT DRY OUT AGM UNLESS THEY CONSTANTLY VENT but you can damage the plates.


Actually it IS very possible to dry out AGM just like a "gelcell" can also be dried out. Just takes a lot of overcharging which leads to popping the vents and all of that moisture which is supposed to be captured and recombined goes right out the vent.

Have seen this with UPS units which were equipped with AGMs from factory, some bad enough that 2-3yrs is the best you will get from them..

AGMs like Gel cells hate being overcharged and actually AGMs are more sensitive to being overcharged than gels.

BOTH AGM and gels are far less forgiving to overcharging than FLA.

See HERE

"As with all gelled and sealed units, AGM batteries are sensitive to overcharging. A charge to 2.40V/cell (and higher) is fine; however, the float charge should be reduced to between 2.25 and 2.30V/cell (summer temperatures may require lower voltages). Automotive charging systems for flooded lead acid often have a fixed float voltage setting of 14.40V (2.40V/cell); a direct replacement with a sealed unit could overcharge the battery on a long drive."

And RV multistage converters can easily do that by staying in bulk or equalization mode instead of dropping to storage mode or staying in bulk or equalization mode too long or too often.

OP has boiled their FLAs to death, fair chance that their setup if not checked properly will do the same to the AGMs.

There are "pros" and "cons" to AGM, pick your poison.

deltabravo

Spokane, WA

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Posted: 11/08/20 07:06am Link  |  Quote  |  Print  |  Notify Moderator

ford truck guy wrote:

DEKA , like stated are made by East Penn Mfg, in Lyons, PA. They are a good battery, with a good following and I don't think you can go wrong with them.


DITTO. I love my DEKA batteries. I installed two Group 31s in my truck camper back in 2015. THey are still going strong.

I'd also recommend a high quality amp hour meter. I use a Victron BMV-712


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jkwilson

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Posted: 11/08/20 07:59am Link  |  Quote  |  Print  |  Notify Moderator

You can get a Deka group 31 AGM (labeled Duracell) at Sam’s Clubs east of the Mississippi for $179 each. If you are patient, they have a sale most years where you can get $20 off on each battery. 4 decent batteries for $640 plus tax is not bad.


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Posted: 11/08/20 01:39pm Link  |  Quote  |  Print  |  Notify Moderator

Ours lasted 8 years+ One time as far as we know, is all it took. The batteries were dry. We paid for them to be as part of storage to be maintained.
I am concerned about over charging.Currently it is set to float charge at 13.5 volts. As to bulk charging it goes pretty high but I don't remember figures. I have hard getting the controller to do as I understand the manual.
I hope these Folks are familiar with it. If not, a trip to the factory, again.

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 11/08/20 01:45pm Link  |  Quote  |  Print  |  Notify Moderator

I maintained a group 24 AGM at a constant 15.6 volts, 24/7 for three months in the antelope valley in 1992. At the end, it had not lost .3 oz of weight. The scale I used was assigned a registration number certificate with NIST. The popoff valves were intact. It was not a Chinese battery.

Out of (perhaps) ten batteries I tested for RAMCAR battery, the lowest voltage encountered that popped an overpressure vent was lower 17's.

So absurdly high that I have seen few legitimate AGM vented batteries. Warpage of plates is the usual suspect in AGM overcharging. And plate deformation is sure and certain death.

Anyoneone who cannot maintain the common sense to avoid mistreatment of posessions needs a room key not an RV key.

Gdetrailer

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Posted: 11/08/20 03:13pm Link  |  Quote  |  Print  |  Notify Moderator

down home wrote:

Ours lasted 8 years+ One time as far as we know, is all it took. The batteries were dry. We paid for them to be as part of storage to be maintained.
I am concerned about over charging.Currently it is set to float charge at 13.5 volts. As to bulk charging it goes pretty high but I don't remember figures. I have hard getting the controller to do as I understand the manual.
I hope these Folks are familiar with it. If not, a trip to the factory, again.


13.5 float voltage will easily take out FLA by boiling them long term, that is what killed your current FLA.

For best FLA storage, that needs to drop to 13.2V!

According to Battery University, 13.5V-13.8V is supposedly compatible with AGM but with any type of battery that you cannot add water that WILL eventually kill them by either drying them out or eventually warping them. Both results are from overcharging.

Most UPS units are set at 13.8V-14.0V which dramatically shortens the life of AGMs in standby use (typically have to change UPS AGM batteries every 2-3yrs).

I personally use 13.2V for long term float of Gel and AGM batteries for my own designed device use. With that voltage I can easily get 10yrs out of AGMs and Gels.

Once it is fully charged and in storage, there is zero reason to keep hitting AGM, Gel or FLA with anything above 13.2V unless you are equalizing (and that is questionable on AGM or Gel).

Storage mode, you only need to give it enough voltage to "maintain" the full charge, in other words just enough charge to take care of the self discharge. Self discharge on AGMs is much less than FLA so they require far less charging..

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 11/08/20 04:57pm Link  |  Quote  |  Print  |  Notify Moderator

This is puzzling. I maintained 13.45 volts on a pair of 31 AGM lifelines for 9 years and one retains 97+ % capacity the second 94+% capacity. I have lots of trouble lifting their weight but when I moved in August neither had lost .03 oz I never detected .1 degree F Delta T in float nor >2°F max bulk @ 80+ I

Capacity testing requires nichrome ceramic windings to keep wattage discharge constant.

Not only do I use Moore thermocouples but adhesive thermal tattletales as well
Once they turn black the game is up.

I am due to capacity test the 31XT Next week. I have not grounds to disagree with the Concorde standard charging graphs which degrade with temp for compensation.

BFL13

Victoria, BC

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Posted: 11/08/20 05:43pm Link  |  Quote  |  Print  |  Notify Moderator

AFAIK, storage voltage spec 13.2v is at 77F so in colder temps you have to adjust that higher (is a table for that)

Sticking to 13.2v (for 77F) at 35F would be way under what 13.2 is supposed to do at 77F


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MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 11/08/20 06:41pm Link  |  Quote  |  Print  |  Notify Moderator

Must obey what the battery likes and ignore what the owner prefers.

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