hi guys, i stopped using lead acid batteries ages ago they are shit and leak everywhere. these are 123A lipo4 cells and they are quite literally tiny. a quick google search should spew up a ton of info. they are wired in parallel to keep the voltage at a nominal 13.2V and they work way better than traditional batteries at a fraction of the weight. for everything <600cc 4 cells should do, but if you go bigger you will need 8 cells. they are wired like this, from one end through to the other end, negative to positive to negative to positive to negative etc. its called a 4s1p confiquration. the 4s denominating the cells and the 1p the parallel wiring.
these are also available commercialy under the name antigravity batteries and a few others, exact same thing except its covered in shrink wrap and the price has been quadrupled. you can buy A123 cells on ebay, most guys ship for free and i think some guys will solder the packs up for you if you tell them what you want.
i'm no electrics whizz, but ive always used these batteries and they are the dogs bollocks.