Divide watts by volts and you will have amps.

So in this case, 12W / 12V = 1A.

The safe way to run 12V DC stuff is to plan for twice the current and never
run less than a #14 stranded wire for small loads & never run less than #10
stranded wire for larger loads up to 30 amps. And use good crimp on or
solder on terminals - no Harbor Freight crap. Also, if you ground to your
chassis, remember it's half the circuit.

Tom
www.towercooler.com

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
neil n
Sent: Friday, July 09, 2010 8:08 PM
To: vanagon@GERRY.VANAGON.COM
Subject: 12 Volt Appliances: Correct Formula to Figure Amps Consumed?

Hi all.

Viewing this:  http://tinyurl.com/23utmeo in the store, I wondered how many
amps it would use. On the back it says: 12 Watts, 12 Volts. Only vaguely
recalled Ohm's Law at that moment, didn't obviously know the resistance of
the unit, so couldn't calculate amps used. Bought it anyway.

At home checked current draw. Low -  0.45 amps. High - 0.6x amps

But entering 12 volts and 12 watts here,
http://www.the12volt.com/ohm/page2.asp shows 1 Amp. Here:
http://www.csgnetwork.com/ohmslaw2.html  0.58 amps. They both *appear* to
use the same formula though the latter gives closer to what I measured on
high speed, hence the makers rating I assume.

What am I missing or doing wrong? Or more to the point, what formula should
I memorize?

Looks were deceiving. Had it been over 1 amp draw, I likely wouldn't have
purchased it thus saving time. As it turns out, for my needs,
0.45 amps/hour over a few nights use, shouldn't draw down my group 42 aux.
battery too far.

Thanks!

Neil.

--
Neil Nicholson '81 VanaJetta 2.0 "Jaco"

http://tubaneil.googlepages.com/

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engine
s