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Old 08-17-2008, 05:11 PM   #1
2 Rivet Member
Carson City , Nevada
Join Date: Apr 2008
Posts: 72
Seeking answers - AGM and wiring

I need more battery power. The Standard battery location on my Argosy limits me to a Grp. 24 or maybe Grp 27 battery, so I think my answer is a pair of AGM batts under the bunk, behind the bulkhead in my Argosy 24.I know... one is not supposed to use batts indoors, given that, here is what I would like to do...

1. Retain the existing Univolt converter for 110 use.

2. Add two 100+ AH Deka AGMs in hold downs under the road side twin bed and,

3. Install a Guest marine three stage 10 Amp two bank charger hooked to the city power input.

4. Run the output from the AGM batts to the 12V main distribution.

I do NOT want to use the Univolt to maintain charge on the AGMs I do not think it will do the job correctly.

NOTE: I would like to use the 12V TV feed to maintain the AGM batteries when driving.

I have studied the wiring diagrams, but am not clear on whether can be done, and whether I will have problems... I am leaving for Montana in one month, and want to get this done, installed and working by then.

Can anyone offer their experience to assist?

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Old 08-17-2008, 06:23 PM   #2
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Dewey , Arizona
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I can see a couple of issue beside the fact that the batteries need to be vented outside of the trailer. I rplaced my battery with a grp 27 AGM (Lifeline) and put it into the battery box on the side of my TW. Your Argo should have the same setup.

The battery and converter are tied together at the 12 volt distribution pannel. The battery acts as a filter for the converter. I do not think you will be able to seperate the two as you discribe.

Why not replace the converter and go with one AGM in the battery box at this time. A good 3 stage converter cost less then a good AGM battery.
We can boondock all weekend on one battery and we can back that up with our EU1000i if needed.


Wally Byam Airstream Club 7513
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Old 08-17-2008, 07:58 PM   #3
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Morada , California
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I agree...replace the Univolt with a good 3-stage converter/charger (see and you won't have to worry about overcharging your main or aux batteries you may add. I'd get a 55 Amp rated unit when using 3'll get them recharged quicker if you're in the boonies and using a generator every day to top them off.

As soon as you hook your two new AGM's into the main 12 volt buss, the Univolt will try to charge, and probably OVER charge these new batteries...unless you were to hook a high rated diode in the circuit.

Also, if you do wish to add the second charger as you mentioned, you should probably get one with a higher Amp Rating than 10 amps. If you run those AGM's down, a 10 amp charger will take hours and hours and hours to recharge them...I'd get at least a 35 amp charger, but a 45 or 55 would be much better...AGM's can take the higher rated charger's output without damage, as long as the charger's voltage is regulated around 14.2 volts.

All in all, replacing the Univolt is the best, easiest and most efficient solution, IMHO.

One other thing, If your mounting location of the new AGM batteries is very far away from the main 12 volt buss, you'll have to use large cable to avoid voltage loss...if you're 10-15 feet away, I'd use at least #4 AGW cable.
Ray & Pat; Morada, CA
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Old 08-17-2008, 10:13 PM   #4
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Carson City , Nevada
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I am looking into a 55 amp converter/3 stage charger to replace the Univolt. Getting the AGMs next week, too.

Thanks again.
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