Found a good 6v battery
 

6v 110mA same width as a zip battery but 50% longer. very doable. might even fit under the pcb with a little work.

http://www.zbattery.com/lib/zbattery/px28a.jpg

Cool, keep us posted!

its not rechargeable
 

Its just a regular alkaline battery, you can really recharge it.

Where'd you find it?

I mean you CANT really recharge it.

But if you had a convertable zip, it wouldn't be too hard to make something on top of the PCB to be able to snap these in and out as needed. Could get expensive though.

the battery works fine..i already had my chassis modded for a dual bat under the pcb..so i just plopped this guy in and taped the pcb on top of it..only the pt cruiser body fit...but it hauled a**.

instant acceleration...still would like more current to the motor tho..
(i did jumper a few of the resistors, but the multimeter showed no change to the motor. so that went back to stock)

i then took the battery apart to see what it was made out of and it is just 4 1.5v button cell batteries with a fancy cover. FYI three of these batteries are the exact same size as one zz battery(4.5v).
so you can run about 6 of them under the pcb/mustang body with no problem for a total of 9v@150mA.

with the 6v batt the motor did not get hot.

oh and i did recharge it a few times directly with an ac adapter at 7.5v...

to a point..
it got pretty warm..but held the charge and was perfectly reuseable.

warning:alkalines get really hot when attempting to recharge..you can easily blow them up.