48V UPS uninterruptible power supply without batteries

I am looking for a UPS (uninterruptible power supply) to use in a student project. I need the complete circuitry from the UPS, but not the batteries. I am working on a renewable energy project in my engineering program. I ideally would like to find a unit which operated on 48v internally- that means it would have four batteries inside, wired in series. Let me know what you have and I may be able to use it. I could use any brand: APC, Tripp Lite, Eaton- anything.
Thanks!