APC MATRIX - will adding batteries in parallel extend run time?

hi all, new user / noob,

Here in South Africa, we are plagued with "load-shedding", typically 4-5 hours of no power.

I was gifted an APC MATRIX 5000, as well as a single Smart Cell XR housing.

I have 12 batteries ( deep cycle VRLA 12V 75AH - same as what is normally in the SmartCell) unfortunately additional SmartCell housings are not locally available.

i intend to run the house electronics (Router, Broadband connection, LED Tv's, LED lights - average drain+- 800W ) from the UPS,

If i wire all the batteries to the MATRIX 5000 in 3 parallel banks of 48V, will this result in a longer up time?

I have not been able to locate information on the web explaining the actual metrics the MATRIX uses to determine the run-time?

Additionally - the APC user manuals mention a user-replaceable battery communication card, but there is no mention of a...