when i re cell them i always just use this... it works out really great.
http://www.ebay.com/itm/UPG-6V-5AH-UB645-Replacement-for-UPS-Battery-for-APC-AP200-/191402741759?pt=LH_DefaultDomain_0&hash=item2c907e0fff
http://www.ebay.com/itm/UPG-6V-5AH-UB645-Replacement-for-UPS-Battery-for-APC-AP200-/191402741759?pt=LH_DefaultDomain_0&hash=item2c907e0fff