Headlght draw?

[jack99]

When driving my car at highway speeds with the lights on low beam ,I have a negative draw on the amp gauge of about 4 amps ( if it is accurate). I s this normal? I have original style head lamp bulbs. Generator charge fine also. Sometimes up to 10 amps if battery is low.

thanks

[Mitch//pa]

yes

[BILL WILLIAMSON]

That's why folks would drive country roads, on MOON LIT NIGHTS, with only the park lights on.
Bill W.

[jack99]

So, I take it that it is normal. Thanks Steve

[Mitch//pa]

if you do alot of night driving you can adjust the 3rd brush but the best bet for all around use is installing an EVR. electronic voltage regulator.. they are hidden

[pooch]

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This is one of the reasons why cars changed to 12 volts.

Less amps drawing and being able to use lighter cable and save weight and money .

OHMS Law.

amps = watts X volts.

If your low beam is 35 watts and tail light is 6 and dash light is 3 ?, that is 79 watts plus ignition running at the same time.

Divide all this by 6 and that will give you amps with engine not running, and only approximately, because a static battery could be anywhere from 6.8 down in volts.

Running, you could have 7 .2 volts, so a good system should draw about 11 amps plus ignition with lights on and running.

Try blowing the horn at night and watch the amp gauge.

[mshmodela]

As mentioned above, Ohm's law you should see a drop when you step on the brakes. Example, after I installed a center LED brake light, I saw little more drop as expected.

[fiddlybits]

not to be picky...but ..... amps = watts / volts.

(which you verbally described correctly)

[Kevin in NJ]

As I recall, my brother is running the direct replacement halogen bulbs and a generator.
His generator is putting out a measured 20 amps by a modern amp meter.

His battery life is running about 5 to 10 years per battery. He is aware of his car and charging. On long drives he will run his headlights to not over charge his battery. He has a band voltage regulator, but has not seen enough need to put it on the car.

Keep in mind the battery is a storage device. It is ok for there to be a negative charge rate for a while, the battery can handle it quite fine. The high amp negative bursts for the horn are fine too, that is why there is a battery. The system works fine if you have good wiring with clean connections and no frayed wires.

Alternators and 12 volts will not make a more reliable or better car. Seems those cars have more issues.

[marc hildebrant]

Just to be correct and it's a cold gray day....


Watts = Volts times Current times Cosine Angle between them.

For resistive load (headlights) the angle is 0 degrees so the watts is just volts times amps.

Marc

[pooch]

Originally Posted by fiddlybits

not to be picky...but ..... amps = watts / volts.

(which you verbally described correctly)

Yup, typing finger in gear, brain not.