MGE UPS Pulsar ESV 22+ connection mystery, help

[kkamel]

Hi
I got 3 of the mentioned UPSs they require external battery box to work, I managed to find the manual but no information about the batteries connection whatsoever, is it 24V or 48V? What makes it even harder is that there are 2 mysterious white pins beside the black and red going out to the battery box, I don’t know if they are mid point batteries measurement, temperature sensor connection or what?
I think MGE systems are gone long time ago and I can’t refer to any technical support.
I am planning to have 2 of them as backup as I have frequent outages, and the third I will scavenge it’s components.
I attached some photos, if someone one have experience with this type of UPS or similar I would appreciate your help.
Thanks,

[kkamel]

Just an update I measured the transformer output it’s 26V, so I think the batteries should be connected as 24V, but I still don’t know the function of the extra 2 white wires going to the battery box?