My flooded batteries are toast in the trailer.I have been buying AGM starting batteries for boat and truck and like them. No maintenance and no corrosion.Thinking of going to two. 6 Volt AGM batteries for the trailer.Would this be a good choice?How do they handle freezing temperatures?

Yes it will work fine. Just don't expect earth shattering charging rates through the 7 pin.

Fully charged wet and AGM batteries won’t freeze. Watch your prices. Two good AGMs will be close to one Lithium battery.

I think you are better off staying with flooded lead acid batteries. Two (or four) 6volt golf cart batteries. They are half the cost and I get 6 or 7 years out of mine before I replace them.

It's all about cost ver. your time for maintenance. I'm like corvettekent. I go for cost........The post telling you to convert to lithium will be coming along shortly. GRIN.Richard

…. I also like AGM for multiple reasons.

AGM Deep Cycle batteries | Good Sam Community

22 Replies

BeenOffGrid
Explorer
Mar 05, 2024
Is it safe to charge the AGM 'Deep Cycle' on front of my trailer via the vehicles 7-pin trailer connector while my vehicle has an AGM 'Starting' battery?
That deep cycle AGM mounted on the trailer also has a solar controller connected to it with two panels on the roof - Wasn't if the deep cycle vs. starting AGM would be a big deal or not but figured you guys may have some added technical on this. Thanks in advance for any input.
- StirCrazy
  Moderator
  Mar 08, 2024
  I wouldn't but many doo. I don't use the charging from the 7 pin as it is designed for a starting battery and in all reality if you havent donne anything to it, it realy isn't doing much when it reached your batteries in the rv. AGM need a custom charg profile to charge properly just like gel, Li and other batteries. I use my solar or the rv converter for all rv battery charging, that will be changing soon on my camper as I will be installign a dc to dc charge for emergency use so I can do the proper profile for my batteries.
  - BeenOffGrid
    Explorer
    Mar 08, 2024
    That makes sense. Gonna try pulling the 30amp fuse under the hood to cut outbound 12v at the 7-pin.
    Right now I have 6x 100w panels keeping that badass 100ah AGM deepcycle topped. It usually uses 2x 100w panels of it's own to a 30amp controller. Things been a great battery since I picked it up (last winter). Using it exclusively for the lift jack, trailer brake-a-way, fridge/freezer, lights, propane heater, etc in conjunction with a 400ah lithium bank.
    Today installed a waterproof 30a receptacle on the exterior of the KZ to connect directly to a 3000w inverter going to a lithium bank. Just getting ready to put the batteries, inverter, and controller back in before the upcoming trip.
    Thought about a DC-DC charger at some point. Did you find any specific brand you like?
- opnspaces
  Navigator II
  Mar 06, 2024
  Yes it will work fine. Just don't expect earth shattering charging rates through the 7 pin.
  - BeenOffGrid
    Explorer
    Mar 06, 2024
    Copy that. Wasn't sure if it'd back-feed to the truck battery as the solar controller is pumping out AGM charging voltage up to 30amps under sun.
    
    Much respect
    Ben
- Grit_dog
  Navigator
  Mar 06, 2024
  It’s fine.
time2roll
Nomad
May 15, 2022
ivbinconned wrote:
The converter is a WFCO 55 amp. I’m sure it’s original In a 2009 Cedar Creek.
Seems to me this converter will not start to even charge if the temps are really low.
Good time to upgrade the converter and stop undercharging the batteries.
Although I assume the WFCO never hits boost voltage putting 14.4 volts on the battery. This is also the reason the charging is terrible at low temperatures.

No particular reason to go 6v in AGM format. I recommend Lifeline if going AGM.

AGM is a bit better at freeze resistance but can still be damaged if low on charge well below freezing.
Flapper
Explorer
May 15, 2022
Per the other question - just like flooded batteries, fully charged AGM's won't freeze until they get to -74F.
I have two Grp 31 AGM's in my boat, that is stored "indoors" but at outdoor temps all winter here in Minn. (Oct to May). This will be year 12 for them. Yeah, I'm pushing my luck, but they have been amazing. Came out of storage this spring still at 95% fully charged. I always just fully charge, disconnect all cables at one terminal, and forget about them till spring.
dodge_guy
Explorer II
May 15, 2022
AGM is far, FAR superior to flooded lead acid. AGM is a much better choice!

Although recently their have been some quality LifePo batteries that ar good quality.
pianotuna
Nomad III
May 15, 2022
Hi,

I'm having excellent results from telecom batteries. I got them at the Interstate store. When one battery in a string in the tower goes bad, they replace them all. They are tested and "reconditioned" and have a warranty.

I do have an upscale charger, and solar, too.

So I got 556 amp-hours of batteries for $395 (usd).

I'll replace them with SiO2 when the time comes.
Veebyes
Explorer II
May 15, 2022
Rather than 2 X 6V GC AGM batteries & have used a single 4D case size AGM. On my second battry now. The first had a lifespan of 9 years. Each year having 5-6 months use with a mixture of mostly with power sites but also some dry camping.
BFL13
Explorer II
May 15, 2022
Do you have a monitor that shows amps and volts so you can tell when during being charged at constant 14.4v they are down to 1/2 an amp per 100AH of bank ?

Do you have a charger that stays at 14.4v until amps get to that at which time you are supposed to drop the voltage to 13.x?

How do you get your charger to do that when you want it to and not before?

Can your charger meet the 20% charging rate specs for Trojan, Lifeline, etc AGMs ?

Is your gen big enough to run the charger doing that many amps?

If so, good to go
ivbinconned
Explorer II
May 15, 2022
The converter is a WFCO 55 amp. I’m sure it’s original In a 2009 Cedar Creek.
Seems to me this converter will not start to even charge if the temps are really low.
Ed_Gee
Explorer II
May 14, 2022
ivbinconned wrote:
I asked 2 questions but have 1 more.
Are they compatible with any “converter”?

AGM batteries are lead acid chemistry....just like wet cells. Should be OK with your converter, but you did not tell us what your converter is. Modern converters usually have a switching setting for wet cells or AGM. AGM batteries have a slightly different bulk charge/absorb charge requirement than wet cells.
Michelle_S
Explorer III
May 14, 2022
I replaced my 4 12V Flooded with 4 6V AGMs 3 years ago this July and not crawling into the front battery compartment to check and add water is worth every extra penny the AGMs cost. I went with Trojan T105 @ 230 AH.