Aa Battery Packs Don't Cut For Powering Screwdriver Motors

"It's a long way to the top if you want your robot to roll" - This substitute for the famous rock saying is what came to mind after I discovered a AA battery pack is fine for the EZ-B board but just doesn't cut it for running 2 electric screwdriver motors through a H-bridge. Initially I thought having a seperate battery pack of 4x AA's would do the trick as each electric screwdriver came with its own rechargeable 3x1.2 AA pack. Things would work for a moment then go pair shaped with the motors not responding or acting strange with the PW sliders. I rechecked DJs diagram on hooking in the H-bridge but still nothing worked as I expected. I finally tried an old RC Parkzone 11.1 V 1300 mah - (14.4wh) battery that powered up a large RC Plane we have and bingo - for a short time the motors were behaving as they should with a 4,3,2,1 d configoration and the PW sliders at 80%. I now realise you need a much more robust battery to run these motors in tandum. I have posted this info for any of you out there that may be in the same or similar loop and not electronically minded.