I got the kit with absolutely no instructions, or info on the motors. I built the kit using the pictures from the link I posted and followed all the instructions regarding installing the motor shield and uploading the code. I don't have a meter to test the battery voltage when the motors are switched on.
OP:
It took me 30-seconds to do a search on "Dagu Magician" and find the original
manufacturer site with info on the motors, etc. 0.8Amp. You should have done
this before even buying the bot. 6-9V from AA cells should power the thing
perfectly well for several hours.
Secondly, you can't even exist in the electronics world without owning a DMM
[digital multimeter]. In the US, at least, you can buy these for as low as $4.00
from Harbor Freight. Even the cheap ones are worth their weight in tantalum.