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Old 03-12-2013, 06:04 PM   #45
jeffnick
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City: Spartanburg, SC
Country: USA
Vessel Name: Big Duck
Vessel Model: '72 Land-N-Sea
Join Date: Feb 2012
Posts: 437
I had a group 31, 100ah AGM battery dedicated to my Freedom 30. It gave up the ghost after 25 months. I paid $250 for that battery. The local Batteries Plus store said the 24 month warranty had expired. I needed to decide what to do. Options were:
Direct replacement
2 12 volt batteries
2 6 volt batteries

My initial thought was to go with 6V flooded golf cart batteries - I'd get more capacity?

Then I thought if I had trouble with one of those 6 volt batteries, the other would be useless.

OK then, maybe 2 12volt flooded batteries? For ~$200 I could get my 100ah.

Trouble was, if I went with flooded, I'd have to relocate the battery from inside to the engine compartment.

I got 10' of 2 AWG cables and glassed a platform in the engine compartment for the two 12's. The 3000 Watt inverter specs say it is able to charge at 130 amps. 3000 watts and 130 amps are both above the capacity of 2 AWG, but I'm only powering the 1.2a 120 vac fridge with the inverter. If things don't work out, I'll run another pair of 2's alongside the ones I have.

Then my brother-in-law goes to his Batteries Plus store and they replace the battery because it's under a 3 year warranty. The list on the new battery is ~$400, but it shows a 5 year warranty of which they only offered me the remaining 11.

After figuring the platform size needed for the two 12's, I discovered that for 100ah, 2 6's or 2 12's would take up about the same space as the 31 and they are all about the same weight. I concluded that weight/size pretty much dictate capacity no matter which format you choose, so for me, next time, I will go with 2 flooded 12's.

I just checked the 8D specs. They fall pretty much in line with my weight/size assumption, but who wants to mess with a 140# battery?
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