Opinion Please on These AGMs for an RV

Good info and advice all round, thanks! It's a good thing that place is a two- hour drive away and another two back, or I'd be there sorely tempted.

I might still be going up there after more figuring where I stand with my existing batteries looking ahead (the Wet ones are still good, but not for much longer-another year or two), but at least now I know what's what. Thanks again.

MrWizard wrote:
'stationary' .. I think that is for the fact they are designed to be rack mounted

This had crossed my mind too. Skinny footprint.

Also, - location of terminals. The manual shows 2 types, one has terminals on top. Another one is "top front" where the "top" is covered with plastic cap but I don't see terminals on "front".
OTH, the Craigs photo shows top (covered) and front that is NOT covered, so this might need some special arrangements.

Hi Phil,

These are a special subset of AGM. It is best to treat them as if they were flooded (following correct charging voltages). The other difference is they do not respond well to super high loads, such as engine starting.

Because the chemistry causes them to need slight higher voltage for charging, I get almost NO recharging while driving. In fact, they tend to discharge. (3 or 4 amps) to the chassis. I did try to solve that by putting an AGM starter battery in place, but it did not solve the issue.

pnichols wrote:


John, as you know ... AGM batteries have lower internal resistance than flooded batteries. One can see this right in their specifications.

This lower resistance means - per basic electrical principals - that they will accept a higher charging current at any applied charging voltage.

That is important for part-time drycampers who want to stay with their stock onboard fixed voltage converters - plus short drives between dry camping spots - for charging of their coach batteries. We elected to stay with our stock converter and go with more-$$ AGM batteries, as opposed to paying more-$$ to retrofit with a multi-stage charger and staying with less-$$ flooded batteries. This combination has worked out well for us over the past 11 years with respect to our camping style.

I guess we could have done both to optimize - spend the $$ to retrofit with a boost voltage charger plus spend the $$ to switch to AGM batteries - but the dollar value would have not been worth it to us to do both of these things.

'stationary' .. I think that is for the fact they are designed to be rack mounted
the foot print is not a vehicle designed format

internal construction should be just as rugged as all other TelCom batteries

that 12.9v on the meter looks good
grab (4) that read the same voltage
do a load check, pay the man take them home, do a recharge

seriously if I was shopping batteries, and they checked out, i would get several and have NO Qualms about using them

i say (4) instead of (2), because it makes that big inverter draw easier on the batteries, lessens the 'Perkuit" effect


i did 50-90 with my first set of AGM, they lasted 5yrs full time off grid use,( that could give 20yrs partial use ?

on this set i'm doing more full recharge almost every day, at least during a/c weather
so far in over one year of use , IIRC they have not been below 68%
most of the time morning LOW is about 80%, depends on how late i stay up, and if we need the fans overnight

BFL13 wrote:
My reason for AGMs over Wets is where I have to mount them inside, where the fumes from Wet cell batts is unacceptable.

There you go. One big reason that people sometimes forget to mention. Was my reason, too (also, very long storage without maintenance charge).

Float voltage times the number of batteries in string? What, didn't have your coffee yet? :)... They explain to unknown but apparently large percentage of dummies in the customers base that volts are added in series. Though I didn't read the rest of the manual.

wa8yxm wrote:
However I have found NO advantage of AGM over flooded wet cells with the exception of the absence of a "This side up" label (AGM's can be mounted in most any position you choose).

John, as you know ... AGM batteries have lower internal resistance than flooded batteries. One can see this right in their specifications.

This lower resistance means - per basic electrical principles - that they will accept a higher charging current at any applied charging voltage.

That is important for part-time drycampers who want to stay with their stock onboard fixed voltage converters - plus short drives between dry camping spots - for charging of their coach batteries. We elected to stay with our stock converter and go with more-$$ AGM batteries, as opposed to paying more-$$ to retrofit with a multi-stage charger and staying with less-$$ flooded batteries. This combination has worked out well for us over the past 11 years with respect to our camping style.

I guess we could have done both to optimize - spend the $$ to retrofit with a boost voltage charger plus spend the $$ to switch to AGM batteries - but the dollar value would have not been worth it to us to do both of these things.

SoundGuy wrote:

BFL13 wrote:
Any more ideas?

No battery is worth anything unless you have the proper means to recharge it. Seems Deka has some pretty specific requirements for these jugs.

I have PowerMax adjustable voltage chargers. I can recharge any 12v to any specs. :)

If the AGMs were in a "string" then I would have to do one at a time or rewire to parallel for the recharge, then put them back in series.

I would only be using them in parallel anyway. I am not going up in voltage like some guys here have done. No reason to in my case, but there is nothing wrong with doing that if you need to.

My reason for AGMs over Wets is where I have to mount them inside, where the fumes from Wet cell batts is unacceptable. I do know there is still a risk of venting from a big overcharge, so I don't do that.

The AGMs I have now suit my 50-90s etc. I am not so sure about the telecom type. I can maybe see them for when on solar doing say 75-99s but not so much for sustained 50-90s. Just don't know, which is why am asking. Mr Wiz and PT seem to be doing ok, but might have different AGMs from the OP type. Not too clear!

The Golf Car shop up-Island I got my used T-1275s at is near this place that has the funny AGMs. For the same price, I would get used T-1275s again most likely. Don't know enough about it--yet :)

I am sure they are fine and are from a good manufacturer.

You want a 'deal' and a project I say go for it. Offer $50/ea and take them all.

I'm not sure about the "Ruggedness" of them physically and thus will not comment.

However I have found NO advantage of AGM over flooded wet cells with the exception of the absence of a "This side up" label (AGM's can be mounted in most any position you choose).

No advantage in terms of capacity
No advantage in terms of longer overall life
No cost savings less you get 'em at a fire sale
MAJOR cost increase over flooded wet

This is why I support GC-2 Pairs as the battery of choice.. Best bang for the buck.