I Have old ups device with serial port and use NetAgent mini to monitor ups.
(NetAgent mini is designed as an ultra-compact and convenient tool to remotely monitor and manage UPS system .Mega System Technologies)
i use universal device poller and add oid for this device.you can download attached file and import to universal device poller.
if dont detect correctly:
1-update NetAgent Firmware(replace .bin file with ftp)
2-update MIBs.cfg from customer portal