The Trestar 924 is a three-phase uninterruptible power supply for central emergency lighting systems that provides a 90-minute backup during blackouts. The valve-regulated, lead-acid battery has a 10-year design-life at 77 degrees, and fully recharges in less than 72 hours. Accessed from the front and top, dimensions vary based on capacity, which ranges from 10 to 75 kW.