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[Healeys] BN2 80/100 W bulbs on the PL700 tripod headlights....

Subject: [Healeys] BN2 80/100 W bulbs on the PL700 tripod headlights....
From: richard.ewald at gmail.com (Richard Ewald)
Date: Wed, 2 Feb 2011 20:40:37 -0800
References: <852374.86229.qm@web120512.mail.ne1.yahoo.com> <8CD9069A9685AF6-1850-1CFE@webmail-d023.sysops.aol.com> <4D494635.9020301@chello.nl>
I think you need to go back and do a bit of math.
2 100 watt light bulbs is 200 watts total load.  Divide 200 watts by 13.5V
(system voltage with the engine running) gives you a amperage draw of not
quite 15 amps (14.81) for both headlights on high beam.  The rule of thumb
for fuses is they should be roughly 1/3 higher rating than the expected
load.  One 20A fuse would cover both headlights.  A fifty amp fuse is too
large and would be the automotive equivalent of a penny behind the fuse.  In
other words, using a fuse that large in the system would give you a system
where the wiring would melt to protect the fuse.
Also why 4 25 amp relays?  Kinda overkill isn't it?  If you want to run a
relay, I would suggest getting a highbeam/lowbeam relay from a fairly modern
car.  The headlight step relay from say a Volvo 240 would work perfectly and
would handle the current draw.  Easy to mount, simple to wire, and
waterproof.  What's not to like?  If anyone goes that route, I can supply a
wiring diagram for the relay.
Rick

On Wed, Feb 2, 2011 at 3:55 AM, Oudesluys <coudesluijs at chello.nl> wrote:

> You need thicker gauge wires */and/*  heavy duty lamp connectors, and
> better wire the lamps through 4 25A relays (high beam/dip, L&R). The
> feed wire to the relay is best directly from the battery and should be
> able to handle at least 50A. Also include a 50A fuse.
> Kees Oudesluijs
> NL
>
> [demime 1.01d removed an attachment of type text/x-vcard which had a name
> of coudesluijs.vcf]
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