Tripp Lite bp36 V42 – Smart UPS 3U Rack 36 V external Battery TRIPP LITE EXT BATTERY PACK original cost $1700. sell for $699 (used) Ref: https://www.amazon.ca/Tripp-Lite-BP36V42-3U-Rackmount-External/dp/B000BU6YHC https://www.cdw.ca/product/tripp-lite-smart-ups-36v-rm-3u-external-battery-pack/1234660