Our town's electricity has been off for approx. 30 hours due to damage to the substation. As always, I switched off all the plugs feeding my (sine wave) UPS (connected to my AV system), refrigerators, etc to prevent damage when it is switched back on again (when power surges may occur). During last night while we were sleeping the electricity was restored. For some yet unexplained reason my kids decided to wake up a bit earlier and switch on the TV (they are not allowed to watch TV during a school week)...maybe they just thought that after the extended electricity cut, they deserved some entertainment..? In any event, they did not realise that I switched off the plug and when they switched on the TV & decoder, it did not work. They then switched on the UPS which allowed them to watch TV for a short while it was signalling its distress with beeps and flickering lights (this according to my kids) that it was obviously running out of battery power. They did not realise what the problem was, so next thing it switched off itself and everything connected to it (fortunately I also switched off my AVR manually, so it was not in stand-by mode and should not be affected). I have since switched on the electricity so the UPS should be charging again. QUESTION: Could the battery or the UPS now be damaged? Obviously if I switched everything on, I will know if it is working or not. But it is one thing for it to work, another thing for it to work as it should..?