Originally Posted by quemazon
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
Yeah... I was wondering how far those safeguards went (i.e. safeguards to prevent power when not connected to correct computer model would suck). I do not think the rate should be a problem... I am just hoping the discharge safeguards are on the battery rather than the computer... i can burn DVDs on battery while doing photoshop actions, so i don't think a few amps should be a problem.
I'd also really like to find a U.S. supplier of the 20W osram sylvania ir (high efficiency) mr16s too. if i can get the battery & charger at effectively no cost, i'm willing to splurge on a nice bulb... interested to see if the high efficiency bulbs respond as well to overvoltage as the standard ones... if so, should be able to get nearly 50w/12v worth of mr16 light for around 25w.