we used these which are basically stripped down dewalt packs

http://cgi.ebay.co.uk/12-Pcs-A123-3-3v- ... 1c124cbe23

Or we did consider these pre-made packs:

http://cgi.ebay.co.uk/7S1P-A123-22-4V-N ... 255a7e125f

http://www.hobbyking.com/hobbyking/stor ... rentCat=85

Andy