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Deep Cycle Batteries - 6 volt or 12 volt?


After some further reading elsewhere, I came across something which said that if you connect 2 Group 27 batteries in parallel, they will deliver a total capacity of 210 amp-hours (2 x 105 AH). This assumes that the average Group 27 battery delivers 105 AH. Two 6V Golf Cart batteries connected in series delivers 225 amp-hours (Trojan T105 rated at 225AH).

Now I have some questions:

1) The staying power of the golf cart batteries is not much better than 2-group 27's (225 vs. 210). Am I missing something here? Is there more to this than I understand?

2) If I use a pair of golf cart batteries, can I use my standard 6V/12V battery charger to charge them or must I use a charger specifically designed for Deep Cycle batteries? I also have a charger for Deep Cycle batteries but it only works for 12V batteries.

3) Would it be correct to assume that if the Charger/Inverter installed in my trailer is adequate for charging my single 12V deep cycle battery (Interstate SRM 24), then will it be OK to use with a pair of Trojan T105 golf cart batteries, or for that matter, two 12V Group 27's wired in parallel? 4) Would it also be correct to assume that my truck's alternator will be able to deal with charging either configuration mentioned in question 3?

Thanks in advance.



1) Although the 2 12VDC deep cycle batteries in parallel and the 2 6VDC batteries in series are similar in amp hour capacity, it is the longer life of the 6 volt batteries that is attractive. In a nut shell, the two 6's use 6 cells overall in the same space that the 12's use 12 cells. This allows room for thicker plates within the battery and that means longer useful life.

2) When two batteries are connected together, they become a battery bank and the 2 6VDC's connected in series can be treated the same as a 12VDC battery or 2 12's in parallel. As long as you leave the 6's connected together you can use your 12 volt battery charger on them at 12 volts.

3) Yes, your on-board converter will charge the 6's or the 12's. Most converters have a fairly "dumb" charger, some are adjustable to better suit the purpose they are used for, and the newer ones will charge at a higher rate. (up to 40 amps or so)

4) The wiring size and length of run from your alternator to the batteries will determine the amount of amps that are available to charge the battery(s) while underway. The trailer plug connection will only accept a 10 gauge wire and the distance from alternator to battery can be 30 to 40 feet - in other words, the charge rate will be slow.

PS your present group 24 Interstate has about a 55 amp/hour capacity - pretty feeble!

Hope this helps.

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