The ACs are not powered by the UPS in a datacenter, only by the generator.
DC UPSes are meant for computer/network gear only and will become very unhappy if you try to power ACs from them - chances are the ACs would get pissed off as well. No need to try in the first place since you can do perfectly fine without cooling during the few minutes it takes for the generators to start.
Biting the hand that feeds IT
