PV Gap

Dan Said:

using a battery to power a 90w light?

We Answered:

From the specs on ebay the solar light runs on power from 85 volts to 265 volts. I'm assuming this will be AC power so you will need an inverter that will handle the 90 watts. I'd get a slightly larger one around 150 watts so it isn't maxed out. The 12 volt battery should be a deep cycle battery if possilbe so it won't wear out quick. A regular car battery will work but if you discharge it too far it will wear out quickly. A deep cycle battery will have an amp hour rating on it. This will tell you the length of time you can draw one amp for. Your inverter will have to supply 90 watts and most of them are 90% efficient at least which turned around will mean you should expect to use up about 110 watts from the battery to make 90 useable watts out the other end of the inverter. Doing the math Watts = Volts x Amps so 110= 12v x A which means about 1 amp for easy calculations. Therefore its an easy answer => just use the amp hour rating on the battery to tell you how long you could charge it before it will die. I wouldn't recommend you discharge it that far but 50% would certainly be ok. So now just divide your amp hour rating by 2. Sorry for the long answer but I just wanted to be thorough. You can probably use this thing on a deep cycle battery with a proper inverter for 2 days easily.