If you are talking about rebuilding a 7B pack, Batteries Plus used to do it for about 20-25% cost of new. Do a Google search on rebuild 7B battery pack and you will find some companies perform this service.
Can't you just buy new/additional batteries for a 7B? Pretty sure they're modular, as I've always gotten spare batteries when I've rented 7B's for shoots.
Yes, I've purchased a new battery and the performance is excellent. With a new battery purchase price of $500, it makes sense to restore the old as a backup. Thanks to davenfl for the Batteries Plus lead.
