How many amps?
Submitted: Thursday, Jul 02, 2009 at 14:36
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Louie the fly (SA)
Hey electrical gurus, how many amps does a 12V 20W lamp draw? What's the formula for working this out? I'm going to build an overhead console for my 4runner and am trying to work out what type of lights to put in.
Louie
Reply By: Best Off Road - Thursday, Jul 02, 2009 at 21:05
Thursday, Jul 02, 2009 at 21:05
Louie Old Son,
I;m not sure this has been answered in a way to help you work things out in the future.
I'll have a crack.
Watts = Volts x Amps
Amps = Watts divided by Volts.
That is to say a Kettle that draws 2400 watts at
home will use 10 amps (because it is on a 240 volts source and 2400 watts divided by 240 volts = 10 amps).
However should you use the same kettle (assuming you had an inverter big enough) in the bush it would draw 200 amps, 2400 divided by 12 = 200.
When I say amps, I should say amps per hour. So the kettle that draws 200 amps, if only run for 3 minutes would take 10 amps out of your battery. Gas would be better LOL.
Jim.
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Follow Up By: oldtrack123 - Thursday, Jul 02, 2009 at 22:11
Thursday, Jul 02, 2009 at 22:11
Hi Jim
As you say A 2400watt kettle on 12v would draw @200amps plus some extra for inverter efficiency loss.
THE formula for "amphrs" is ;- Load amps X time in hrs
200 x3divided by 60= 10 amphrs
Also this is incorrect""When I say amps, I should say amps per hour" you should say amps!!
Also this "if only run for 3 minutes would take 10 amps out of your battery."
It will take10 amphrs from the battery.
Correct terminology is ,I believe, is important in tecniical threads .
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Follow Up By: Welldone WA - Friday, Jul 03, 2009 at 01:03
Friday, Jul 03, 2009 at 01:03
A wise old electrician once told me there are only 2 fundamental rules/laws of electricity:
1/ "Electricity is contained in smoke'' . If you have an electrical device that suddenly emits smoke , this is a
sign that the electricity is escaping! If enough smoke escapes than the said item will cease to function , 'cause all the electricity has gone!
2/When wiring,it is important to remember: "Red to Black = Blow to Bits!" Failure to follow this rule can lead back to rule 1/
Cheers ;))
Welldone
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