By this update I wish to offer a bit of information which possibly this will save you some cash when using this UPS
XL version.
This monster has external plug so other battery boxes to be connected in a chain.
Never though to measure it charging current and I did that today, by a huge surprise this found to be limited at 9A ...... according to most 12V 17A lead acid specifications their recommended charging current is half than what this UPS it is limited to.
A bit of further research made me to understand that the most healthily battery configuration for it, is this to be used with at least one external battery pack connected to it, so it charging current this to be shared at both battery packs.
Now in case that you need to avoid using several 12V 17Ah battery packs, another and Ideal solution is to build your own pack with two 12V 36Ah cells.
Most or all 12V 36Ah cells comes with charging current specification of 10~12A and this is even higher than what SUA 1000 XL it can deliver, eventually with such a power pack I would expect and a even more prolonged life cycle of such a battery pack.
In my case those Panasonic 17Ah with 10 years life cycle they did collapsed in 6,5 years, and even with out my UPS to engage in any power failure, this translates that them was always topped up, and that the charger of my SUA 1000XL did not have the opportunity to give them a hard time.
by testing right now another battery pack with two 12V 36Ah cells, and by performing UPS calibration, I am now gained three hours run-time on battery which this is great news.
Charging current started at 9A but in a minute or two this stabilized to 8A for an hour or so, before this starts dropping to a lower value.
I got a picture as souvenir.