Originally Posted by Denniscw
You would need 8 6volt bTteries to replace 4 12volt batteries.
You sir.... Just flunked math class.
The proper answer is: NOT ENOUGH INFORMATION.
Here is why (And the info the OP needs to pass math class)
The most common six volt battery is the GC-2 Golf car battery, depending on just where adn what you buy these run around 220 amp hours give or take about 5 percent, so we can use 220 or 230 as our amp hour rating for each pair..
(Each pair of six volt makes one BIG 12 volt battery, and please think of the pair as a single 12 volt, makes life (Well explanations) so much easier)
Now. IF you existing 12 volt are size 4D: Then Dennis is right, What are the odds of them being 4D? (Approach zero)
Here are some common 12 volt battery sizes,
Group 24 about 75 ah each so 4 of them is 300 amp hours
If you replace with 4 GC-2 (Same tray but taller) that's 460 AH, so that is over 175% the power at the first pass (it gets better)
Group 27 is about 95 amp hours so times 4 it is 380 You are still better with GC2
Group 29 is around 105, Times 4 is 420 and you are still better with GC-2
Group 31 is 130 times 4 is 520 and that beats 4 GC-2.
Source: assorted battery maker web sites. NOTE that capacities do vary slightly from brand to brand and sometimes from model to model within the brand.. Note also all capaciteis listed are at teh C/20 (20 hour) rate.
And from the above, you can find the answer which is
Yes, Yes, Yes, NO for most battery sizes.
Oh, I mentioned first pass
DEEP CYCLE batteries such as the GC-2 Golf car are designed to take a 50 percent discharge (Discharge to half full) and back without seriously shortening the battery's life, they stand a fair chance of surviving even deeper discharges.
MARINE/Deep cycle are first and formost starting batteries, by the time you get down to 50 percent you are already doing damage, they are not designed to go that low.
Unless you get Group 31 TROLLING batteries (not marine/deep cycle) this changes the answers to all yes.