Originally Posted by dougr
Is it possible to use a Li-Ion laptop battery for driving a lighting system? I'm thinking about driving a 12v/20w mr16 with my laptop battery, which is a 14.4v 4.3Ah Li-Ion battery.
Well, let's do some math...12V, 20W, means the resistance should be about 12^2/20 = 7.2 Ohms. You will be driving it at 14.4 V though, so your current should be 14.4/7.2 = 2 Amps. The power should now be 14.4^2/7.2 = 28.8 Watts. Lithium Ions don't like high rates of discharge, but 2 Amps should be fine for a 4.3Ah pack. On a full charge your run time could be as high as 2 hours, BTW. Sound like a pretty good setup. Let us know how it works. Don't worry about frying your battery pack, BTW. Those packs have a lot of safeguards in them to prevent damage from a full on short.
Nathan