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Date:         Fri, 9 Jul 2010 20:42:21 -0500
Reply-To:     Tom Hargrave <thargrav@HIWAAY.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Tom Hargrave <thargrav@HIWAAY.NET>
Subject:      Re: 12 Volt Appliances: Correct Formula to Figure Amps Consumed?
Comments: To: neil n <musomuso@GMAIL.COM>
In-Reply-To:  <AANLkTim5VAZQ6UOrcV3Vli0MWxT6oD1NmX6czoc_AYJT@mail.gmail.com>
Content-Type: text/plain; charset="us-ascii"

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


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