http://www.apexbattery.com/?ne_ppc_id=67...ID=182999097512 i just ordered a set for my js512 half the price from Apex battery i belive they were 10.95 a piece n it takes 2 just take the old batterys out n give them the exact numbers they are 2 different sets of batterys in the js512's ya can save some dollars hope this helps jb
The originals are two 6v batteries wired in series for a total of 12 volts.
Measure the dimensions of the existing pair and search the net for a 12 volt battery of similar (or smaller) dimensions.
By memory - so double check - the battery pair is 5.5"x4"x2 with about an additional 0.25" required on the 2" dimension for the terminals. Be sure and specify the right terminal size when ordering - there are two common sizes of spade lugs available on batteries of this size.
You should have no problem finding a 12v battery with a higher amp-hour rating that will fit in the same physical location.
This is a much better battery solution than the series combination in the long run. Think of what happens when you put a dead battery in a multi-cell flashlight - it doesn't matter how good the other(s) are - that one dead one kills the whole shootin match.