The correct UPS battery cable size depends on the current load (amps), cable length, and system voltage, with 2 AWG to 4/0 AWG being common choices. Getting this right is not just about performance—it's about safety, efficiency, and extending the life of your equipment. On the other hand, overly thick cables can be unnecessarily expensive and. The internal wiring is built in the factory and adapted to the characteristics of the devices. I am looking for some feedback for wire sizing for DC cables that run from battery storage cabinets to a 300KVA UPS. I have been in this business for 40 years, but 99.