A G M Batteries

[Bud99]

Are A G M Batteries worth the extra money? Do they outlast wetcell Batteries or am I just as well off buying 2 wet cell batteries for use in my 5th wheel?
Thanks,
Bud99

[pnichols]

My RV's two 12V 100 amp hour Interstate (probably made by C&D Technologies for Interstate) AGM true deep cycle wheelchair Group 29 batteries are in their 8th year.

These batteries see the stock ~13.8 volt RV converter most of the time - the RV converter being powered by a 4000 watt Onan built-in RV generator, or a 650 watt portable Honda generator, or shore power. These batteries also of course get hit with the engine alternator hooked up in parallel with the engine's wet cell charging battery via a silver alloy contact solenoid when we're traveling.

These two batteries just sit there, shut up, and do their thing month after month. However I do dust them off about once a year if I don't procrastinate my way out of it. I'll never use wet cell batteries again in our RV. I'd really like to move up to a couple of 12 volt Lithium RV batteries if their prices eventually come down in the common Group 27/29/31 sizes.

[christopherglen]

If you are going to do ALL the maintance, get the wet cells. If you might do it, or already know you will not, get the agm's.

[greenrvgreen]

Looking on Amazon, low-priced grp 31 AGMS are available in the low- to mid- $200 range, while the Lifelines approach $400. IIRC I paid $80 each for my Costco GC-2's.

[brulaz]

Almot wrote:
It should be noted that between cheap Chinese UB/UPG and expensive Lifeline there are US made EastPenn/Deka and Full River, a lot cheaper than Lifeline.

Yes, last time I looked, Sam's Club was selling Duracell AGM GC2s or 31s for US$180 ea. Rebranded EastPenn/Deka I think.

[Almot]

It should be noted that between cheap Chinese UB/UPG and expensive Lifeline there are US made EastPenn/Deka and Full River, a lot cheaper than Lifeline.

[Bud99]

Thank you all so much for your time and wisdom!

Bud99

[greenrvgreen]

For gadget-enhanced tenting, I've started using AGMs in small form-factors (35ah, 14ah). Results so far have been very good, although I will say that a weak/worn out AGM is VERY weak.

Biggest difference to me is that these batts handle like dry cells. I transport them inside the car and recharge them inside the tent (very well ventilated). Can't speak to longevity yet, although I will say that AGMs are VERY pricey, and I'm using the cheapo UPG batts. I cannot imagine paying out for a set of Lifelines for the TT--I'll stick with the cheap Costco GC2s.

[Almot]

To me AGM was the only choice because I had to store it for a year without any maintenance or trickle charging. It went from 100% full to ~60% in a year. Flooded batteries would've discharged to zero and below over same period, and wouldn't be of much use after this.

[pigman1]

mena661 wrote:
.... It seems a lot of people here use solar in conjunction with AGM's so my guess is they're using temp compensation.

Actually, two temperature compensators, one for the solar charger and one for the charger in the inverter. Works well.

[rottidawg]

And for some of us there is no choice but AGMs.
Many campers (my FWC for one) have the batteries vented to the interior.
I am also done forever with the corrosion and maintenance of flooded batteries in every vehicle I own.

[Almot]

mena661 wrote:
It seems a lot of people here use solar in conjunction with AGM's so my guess is they're using temp compensation.

Yes. Going for extra cost of AGM, would've been stupid not to use temp comp.

[mena661]

kccwoodworks wrote:
What no one has mentioned yet is AGM's don't gas. They don't need to be vented therefore are safer. The only place for batteries in my van is inside where a wet cell would be dangerous.

AGM's DO gas if you overcharge them. And "overcharging" can be using too high a float voltage in hot weather. Another member here confirmed that in his testing (HiTech). You don't want AGM's to outgas. Keep your voltages close to manufacturers recommendations and use temperature compensation. It seems a lot of people here use solar in conjunction with AGM's so my guess is they're using temp compensation.

[Almot]

BFL13 wrote:
It is a specialty situational thing whether the AGMs would be worth it to YOU.

Besides the situation where you cannot get at your batteries for hydrometer and water level checks easily, making AGMs better, the other thing that really came to light in previous threads here was (as mentioned above) little voltage drop under heavy load.

Yes.
Take AGM if it's difficult to get to batteries.
Or if you expect high loads.
Or if you need to keep them inside your living space.
Or if you need to store them for +6 months without any maintenance or float charging.

If those are YOUR situations, then AGM is worth extra money. If not, then they aren't worth it.

Extra cost can be anywhere from 40% to 100%, but you aren't going to buy them every year so this is manageable.

[2oldman]

pigman1 wrote:
The big selling point for me is no need to add water, and absolutely no corrosion....EVER.

You got that right. I got pretty weary of the maintenance of watering. It takes some big pockets to buy your way out of it, but it's really nice once you do.