APC Smart-UPS Ultra Lithium-Ion Battery Pack 1U APC Smart-UPS Ultra Lithium-ion 1U External Battery Pack for extended runtime on Smart-UPS Ultra 3kW systems. Up to 10 external batteries can be connected. Number of rack unit 1U Battery type Li-Ion (Lithium-Ion) Provided equipment- Rack mounting brackets, Vertical mounting brackets Number of battery free slots 0 Number of battery filled slots 0 Battery voltage 50 V Ambient air temperature for operation 0…40 °C Operating altitude 0...10000 ft Relative humidity 0…95 % non-condensing Ambient air temperature for storage -15…45 °C Storage altitude 0.00…15240.00 m Storage Relative Humidity 0…95 % non-condensing Mounting mode- Rack mounted with kit, Tower mounted with kit Compatible Batteries- SRTL50RMBP1U-LI