Hi Jim,
Ok, $900 does not sound too bad compared to $3500 but you have to match the packs with some of your old once to run it. The first thing that comes in mind is a standard starter battery tester like this one: http://www.biltema.se/products/product.asp?iItemId=88165
I think you have the same kind on your side of the pond for $49.95 or so. I am not sure how much you are allowed to load the packs but used on one pack at a time (14.4V fully charged) it will sure reveal any bad packs. Attach the tester to a pack, flick the switch for a few seconds and you’ll know! 8)