12v ride on kids jeep?

Hi everybody, Just wondering if anybody can help me, ive recently been given a electric jeep for my kids to ride round on, proplem is its a bit sluggish on hills when it is loaded with the two of them, it has 2 12v motors on the rear wheels, and 2 6v batters connecter in line to make 12v, these are 10ah batteries. If i upgraded the 6v batteries to 1 12v 20ah battery wiuld this make the jeep more poerful or would i have to upgrade the motors? Any comments or help would be much appreciated, Will parry

The 12V-20AH battery provides longer reserve, but it's power delivery will not be any greater except if low "path" resistance. Resistance may be lower with the one less battery interconnect and the bigger 20AH having a low internal resistance. The voltage drops to the motors may be high under load, that's improved by better wiring (heavier cables, better grounding, relays). But if the voltage to the motors is fine, the bigger motors are needed.

There is actually a website with a forum on modifying these things http://forum.modifiedpowerwheels.com/index.php?sid=2c89da081d540aa4522c0e0027f39cf6 Here's a cool video of some modified cars/trucks, the guy has 56 videos. http://www.youtube.com/watch?v=mmW5fS4DJNM&feature=mfu_in_order&list=UL