I used 2 x 18ah batteries. I would ideally like to use 2 x 100ah deep cycle batteries but they would cost about R2,000 each... May upgrade in the future hence the Brad Harrison connectors :)
This is an overview of an upgrade to my RCT 2000VA UPS with 2 x 18ah batteries.
*** Consult a qualified electrician to assist you with this sort of project due to shock and fire risks. Working with high voltages is EXTREMELY DANGEROUS. I accept no liability for anyone following these steps. ***...