When the mains cuts out, the 12 volt battery kicks in. When the mains goes back on, it charges up your 12 volt battery. Constant power!There is a solar option, which uses a specially designed 20 watt solar panel that fits directly into the energiser to charge your 12 volt battery. No more lugging your battery inside!Get the Energiser CP1900 from Fenceman.High power / low power: Use the high power to establish the fence with new livestock - once they stop testing the fence switch to low power to conserve battery life. For longer fences it will be necessary to keep the unit on high powerDay mode: Full power during the day had half power at nightNight mode: Full power during the night and half power during the dayPulse rate: This alters the time between pulses from 1 ... More info