Could use some guidance choosing AGM’s.

I recommend a Lifeline brand AGM battery. I believe the charging specs are bulk/absorption 14.4 volts and float at 13.2 volts. If the AGM setting is within 0.1 of that I call good to go. NO equalization.

Deep cycle - maintenance free is fine too.... verify the charging and float voltages. and again NO equalization.

theoldwizard1 wrote:
Off the top of my head, I know of no AGM battery charger that monitors battery temperature.

The CTEK Multi US 25000 offers temperature compensated charging and does a fine job with AGM batteries.

Big Katuna wrote:
All these batteries will ever do is start the genset and run lights (all led) occasionally.

Buy ONE good quality AGM starting battery.

Group 24 has a footprint very similar to GC220

Manual clicky

So the Xantrex is a three way charger. It has Temp Control Charging.
It can be programmed for wet, two kinds of gel and AGM and equalize (with a remote panel).

Not sure from skimming manual if it works without batteries connected (battery eliminator?)
But I don’t care as it will always be connected to batteries.

All these batteries will ever do is start the genset and run lights (all led) occasionally.

So no wet cell or AGM, going with deep cycle maintenance free.

theoldwizard1 wrote:

MEXICOWANDERER wrote:
Golf car size AGM batteries are not superior versus regular BCI size batteries.

Trojan T105-AGM hold about 5%-10% less energy than the FLA T105.

FLA can tolerate higher charging temperature (which usually comes along with higher charging rates).

I'll make this simpler.

The guts of an AGM BCI group 24, GC220, Group 31, or 8-D are essentially the same. The guts of a flooded battery same group sizes are wildly different between the BCI group sizes. Remeasure WATTAGE then come to me and state the difference between Flooded and Absorbed Glass Mat.

That was NOT THE POINT, the point is whether or not a GC 220 AGM battery is somehow superior to a same company group 24,27, 31, or 8-D size battery. Sorry internals are the same. Polar opposite of flooded.

Charging of any battery FLA or AGM should be severely curtailed at 110F then cease altogether at 120F

Try charging a flooded group 31 at the amperage an AGM thrives on and the hazmat response team will be at your front door before you know it.

Temperature control is achieved totally utterly and completely with voltage regulation for any battery flooded and AGM. I set voltage on my banks, flip the ON switch and walk away. The flooded batteries at 29.6 volts need timing/off control. The AGM at 14.4 can go many hours which at 29.6 the flooded batteries at a certain absorbsion amperage would be overcharging to the point of unacceptable heat rise and electrolyte spillage. My 7% antimony Rolls batteries are far and away more sensitive to the effects of overcharging than the Lifelines are.

We're not talking about "Shake The Bottle And See If They Fight, Dewey" high voltage experiments here. I could rectify 240 volts and give both types of batteries a charging enema they'd never forget. But modern battery chargers are voltage limited. And only a garbage-trashed-bad AGM battery would overheat using the control voltage protocol.

I safely stuff 100 amps into a 100 amp hour AGM.
With my 3300 amp hour Rolls battery bank does this mean I can safely stuff 3300 amps into the depleted Rolls batteries? I can only hope this is of some help for you...

Big Katuna wrote:

BFL13 wrote:

Big Katuna wrote:
2005 Freightliner Fleetwood, Xantech Freedom 458 inverter/charger connected to four 6V golf cart batteries, which need replacing.

I would like to replace these with either two 6V or two 12V maintenance free AGMs.

We rarely boondocks, have a gas option fridge and if we need to use the microwave, will start the genset.

What we DO do is leave the RV plugged in all the time with AC on low, which fries the GC batteries. I have the watering system installed but still manage to forget and they get dry.

Are there direct replacement size wise for GC batteries?

If you are nearly always at full hook-ups, all you need is a simple 12v house battery to power the inverter/charger.

You are right that 6s don't like to Float very much. Xantrex even has/had their 3-stagers with the option to turn off the third stage for that reason.

It is the high SG of 6v batts which makes them not so good for floating them. Lower SG batts are better for floating, but have less capacity and discharge rates.

If you do want an AGM go for a type that is low SG and meant for floating such as those UPS types. But why spend the money? You could get a single simple sealed flooded starting battery like for a car to meet your requirements looks like.

Thank you. I think this is the correct choice for me. My sealed engine batteries are on year seven and start the old C7 just fine. Getting ready to replace them on general principals.

I’ll buy four instead of two

My advice there ASSumes, the inverter/charger will "support" any 12v battery to run your 12v loads, and not really draw from the battery much. Also there is generator starting perhaps.

I am not too clear on inverter/chargers for how they actually work on the charger side. I was told on here that they can't run on no battery like a converter can to run the 12v systems, but instead they need a 12v battery to run the inverter/charger and then you are good. But then I also have seen where you have to "enable" the charger, so I am now wondering if having a starting battery or two as house batteries would work out ok.

Needs confirmation from the other guys on here before buying! :(

Big Katuna wrote:
I would like to replace these with either two 6V or two 12V maintenance free AGMs.

Which ever size you choose, make sure it is a TRUE deep discharge battery. Not a starting battery and not a "dual purpose" battery.

Big Katuna wrote:
What we DO do is leave the RV plugged in all the time with AC on low, which fries the GC batteries.

First, see if your converter/charger has a setting for AGM. Likely is does NOT ! Disconnect your converter and connect the DC power distribution panel directly to the house battery bank.

Buy a GOOD battery charger that has an AGM setting. Near where your original converter charger is, install a 120VAC outlet. Buy a cheap MECHANICAL lamp timer. Set it to run for about 1-2 hours per day. Plug that into the new outlet and plug your new charger into that.

When you go on the road, just plug the charger into the other open outlet !

Big Katuna wrote:
Are there direct replacement size wise for GC batteries?

Yes, they make GC2 AGN batteries.

MEXICOWANDERER wrote:
Golf car size AGM batteries are not superior versus regular BCI size batteries.

Trojan T105-AGM hold about 5%-10% less energy than the FLA T105.

FLA can tolerate higher charging temperature (which usually comes along with higher charging rates).

MEXICOWANDERER wrote:
AGM batteries don't like a lot of amperage
when charging. they can't handle the heat.
Just get some deep cycle batteries.


Where in the world did you get that idea?

AGM is famous for safely accepting tremendous charging current safely. Except for tele communications special purpose batteries.

My single regular group 31 Lifeline chomps 101 amperes without even getting warm. CHARGING is done in a controlled manner.

Heat is the issue. Trojan says specifically do NOT let the temp exceed 122F when charging.

Off the top of my head, I know of no AGM battery charger that monitors battery temperature.