APC BACK UPS 650EI 650VA APC's Back-UPS 350EI, 500EI and 650EI offer guaranteed power protection for computers and other electronics in your home or business. Models provide enough battery backup power so you can work through short length power outages as well as safeguard your equipment from damaging surges and spikes that travel along utility and data lines. Together with a variety of standard features, APCís Back-UPS 350EI, 500EI and 650EI are perfect choices to protect your productivity from the constant threat of bad power and lost data.