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How much amperage do halogen headlights pull? I have a power master 85 amp alternator, dual electric fans that pull about 15 amps. An electric water pump that pulls 7 amps, plus whatever the reat of the system pulls to run. As long as I don't have the headlights on the voltmeter stays between 13 and 14 volts with the car at cruising speed. As soon as I turn on the headlights, it drops to about 10 volts and will only come up to about 12.5 at 2500-3000 rpm! The car is only running @ 1450 rpm @ 60 mph so at that speed the voltmeter is only reading about 8-10 volts. Not enough to keep the battery alive. :thud: Art
 

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About 20 amps, if you have the high beams on. About 10 on low beams. Sounds like your alternator is weak. You are only demanding 60 amps, worse case. Might be wise to upgrade to a higher capacity alternator while you are at it.
 

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:agree: 100 watts divided by 12 volts equals 8.3 amps.
So two 55 watt lo-beams = 9.2 amps, plus all your tail & instrument lamps, if I remember right it adds up to around 11 amps total. Click on two 45 watt high beams as well and you're up to 18.5 amps (which is close to the 20 amp rating of the built in circuit breaker in the headlamp switch).
If you have hot rod 100 watt hi-beams, you are pulling over 27 amps in the lighting circuit alone......
Then we add in other electrical loads, resistances, and some voltage drop and it adds up quick.
 

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This one is a new Powermaster 85 amp. I just ordered a 140 amp to see how it fares. I have a 1450 watt stereo also so that figures a lot in the picture if I have it on. I got the smallest pulley they offered also to try to maximize outout at low engine RPM.:cheers: Art
 

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If that's not a joke, you sure lost me!!
Art, it's all the derivitives of Ohm's law....Greg OHM is the guy who figgered it out first...playing with batteries/DC current and resistive loads and doing power calculations in a really olde tyme lab all us geeks would know the history of it....

but then things got complicated really fast with wires and magnets, and power generation discoveries....Edison electric what today they call Conn Ed. in NYC regions...generating DC current for lighting/industrial uses....
the HUGE combat he lost with Westinghouse?? I forget ...over wether DC or AC currents were better, and obviously Edison lost that battle for being rong...he still was a super rich man, and best buddy of Henry Ford....

and so that very particular matter of physics involving a coil of wire, magnetic fields and so has never really been totally explained, far as I know...

the ultimate WHY??? in physics anyway.....

:D :WTF :devil: :crazy: :cheers:
 
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