> I just asked a question about battery capacity for driving a box fan > overnight. The fan motor draws .8 amp, not the .5 I originally stated. > > Well, let's see... 0.8A * 120V = 8A * 12V. Figure on 10% coversion loss through the inverter-- probably less, but best to be conservative-- making it 8.8A draw. 8 to 10 hours of that is from 70 to 88 Amp-Hours. My group 24 Trojan deep cycle (a a very good battery), which is too big for under the driver's seat and lives under the rear bench, is rated at 70AH (5 hour rate) to 85AH (20 hour rate). So at an 8 hour rate I might be able to get 75AH out of it. That'd leave it "mostly dead" every morning. Given how long it takes to charge a battery up off the alternator, I'd say finding a low-amperage 12V fan might get better results. I've seen 2 or 3 of those black computer fans mounted in a little wooden frame stuck in people's windows before. At 0.25A apiece, you could run a couple of those all night and only use 4-5AH. -- John Bange '90 Vanagon - "Geldsauger" |
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