APC BACK-UPS CS 500VA 230V UPS (BK500EI) - Max Configurable Power (Watts): 300 Watts / 500VA, Input frequency: 47 - 63 Hz, 50/60 Hz +/- 3 Hz Auto-sensing, Output Frequency (sync to mains): 47 - 63 Hz Sync to mains, 50/60 Hz +/- 1 Hz Unsynchronized, Transfer Time: 6 ms typical : 10 ms maximum, Number of Power Cords: x 2, Interface Port(s): Optional Simple Signaling RS232 cable, USB, Expected Battery Life: 4 - 6 years