# Re: Amps drawn

```   > =09So, if you have 55w driving lights, and your battery puts out=20
> 12v, the conformulation would be:  110w / 12v =3D 9.17amps.

I have found from actual current measurements that the wattage ratings=20
are not very accurate, so you would be best to use a good Fluke (or=20
similar meter) and actually measure the voltage and the current, to=20
determine the wattage.

The above formula also illustrates why relays work so well.  They get you=
=20
more volts at the light, which reduces the current.  The higher voltage=20

***WRONG***

Current is directly proportional to voltage (if voltage goes up 10%, then
the current flow will go up 10%), and the power dissipated goes up as the
square of the voltage (or the current) change accordingly.

Relays work so well because you're bypassing all the shitty (sorry, but
it's the truth) Audi Factory wiring with [presumably] high-guage direct-
wiring with only the relay between the load (lights) and the generator
(alternator, battery), and using a good [presumably] high-current relay,
so that overall the resistance of the wiring is much less, therefore
you're putting more of the [relatively constant 13.6V nominal] voltage
across the lights, and less across the wiring. The total system voltage
is the same, the lights' resistance is the same, and the wiring resis-
tance is less, therefore more total current will flow, and more of the
voltage dropped across the lights, the lights are dissipating more power
("they're brighter").

How shitty? Well, by the simple, nay even trivial expedient of running
a nice 10ga wire directly from the battery terminal (not the alterna-
tor, which is nominally a better connection point, but a *HELL* of a
lot harder to get to in my UrQ) to the stock headlight switch (bypas-
sing the stock ignition-switch-switched headlight power), running the
rest of the way through the stock wiring harness through the fuse
panel (again...) to the front low beams, I gained over 2 volts at the
headlights! (Went from 9.7V to 11.9V).

If you're not seeing 12V or more (with engine running, electrical system
at 13.6 or more) across the headlight filaments (measured at the headlight
itself, *NOT* headlight +12 to ground!), then a good heavy-ga wire/relay
setup will give you a noticeable substantial improvement in light output.

also gives you a brighter, whiter light.  You can also figure that a good=
=20
alternator is actually making 14v until it really gets loaded down.=F0=E7F=
=D3=F3=F0

-RDH

```

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