Re: She cannah take tha' mooch pawr-r-r, Cahptain!

["Gregory S. Youngblood" <greg@domain.elided>]

I just woke up, so I may be speaking before my brain has fully engaged,
but here goes.

Watts = Voltage * Amps, so if you want to calculate Amps, you use
Amps  = Watts   / Voltage.

Using that formula, your 75w lights use 6.5 amps at 12 volts. Your
100w lights use 8.333 amps. All said, you have ~29 amps of lights running
at 12 volts, 27 amps at 13 volts, or 25 amps at 14 volts.

It's been too long since I've done any electrical work of significance to
remember if 12 guage wire is sufficient.

BTW, what kind of car is this? And, how big is your alternator?

Hope this helps,
Greg

On Mon, 5 Aug 2002, Tony Sims wrote:

> Dear Ampy,
> Following to a recent bout of stupidity, I had cause to re-wire the headlights
> on my car.  Since the original configuration did not provide a relay for the
> low beam circuit, I added one, of 40 amp capacity, and I replaced the original
> high-beam relay with a new 40 amp one as well.  Again, since the original
> configuration did not provide fuses for the high- or low-beam circuits, I
> added a 20 amp fuse to each circuit upstream of the relays.  All the power
> delivery wires from the battery to the relays and on to the high- and low-beam
> headlights are 12 guage wire, and a dedicated ground circuit was created with
> the same 12 guage wire.
>
> Because I did not want auxiliary lamps, I chose to install bulbs of higher
> than original wattage to provide improved illumination.  The main beam bulbs
> are H4, 65w low/75w high.  The high-beam bulbs are H1, 100 watt.  Everything
> seems to work swimmingly, and the system generates an impressive amount of
> light.  It also consistently blows the high-beam circuit fuse after about 60
> seconds.
>
> I double checked the path of all my wires to make sure nothing is shorting,
> and double checked all my connections to make sure they are correct.  It all
> looks good.  None of the wires are getting hot, nor are the relays.
>
> The answer would seem to be that I have far too much wattage (75+75+100+100 =
> 350) running through my high-beam circuit for a 20 amp fuse.  Not being of the
> electrical-engineer persuasion, what I do not know is what to do next.  Could
> I safely increase the capacity of the high-beam fuse to 25 or 30 amps?  Or
> must I reduce the draw by installing lower-wattage bulbs?  I am assuming that
> other than the fuse, my circuit is of great enough capacity, but as previously
> stated, this isn't my area of expertise.
>
> Dear Ampy, please help me!
>
> Dimbulb
> --
> to be removed from alfa, see /bin/digest-subs.cgi
> or email "unsubscribe alfa" to majordomo@domain.elided
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided