Date: Tue, 8 Aug 2017 10:59:48 -0700
Reply-To: Neil N <musomuso@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Neil N <musomuso@GMAIL.COM>
Subject: Re: Fuse Size: Aux battery to fuse block
In-Reply-To: <CY4PR20MB13036448022926072A76DDABA08A0@CY4PR20MB1303.namprd20.prod.outlook.com>
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> Out of curiosity, why would you be connecting "fog" lights to the house
> battery?
I'd read your earlier post about the fog lights. Though somewhat
misguided, my intent was to have no extra loads on the starter battery
that might drain it should I leave that load on too long. But then of
late, I've been carrying a small "jumper" battery pack. I'll be moving
the fog lights to the starter battery.
> For the lights, especially for DC circuits and lighting wattage ratings are
> nominal. For incandescent bulbs, especially halogens actual current can be
> over a wide range affected by delivered voltage and lamp tolerance. 110
> watts at 12 volts is 9.16 amps.
Ok. So if my alternator puts out 13.8 Volts, in paper, I assumed the
fog lights were drawing 7.97 Amps but then in practice, I see how
circuit resistance and bulb design affect actual current draw.
> It is counter intuitive but as system
> voltage drop increases (less voltage at lamp) the bulb will run cooler and
> current draw can actually increase. A fuse in its simplest form is a
> resister. It will also introduce a voltage drop. Operation a fuse near its
> full rating will cause it to heat up and can cause nuisance failures. As the
> fuse heats up some of that heat goes to the socket and over time does damage
> there.
Yes. Right. So this might've have been a factor behind the melted
terminal insulator I saw at the OME 30 wire from starter battery to
fuse panel.
>..... For the house battery, the charge line circuit however you
> did that needs to support charging the battery (20-25 amp) and all those
> connected loads.
Last night I thought more about the charge wire gauge between starter
and aux battery. That battery has 3 potential charge sources
(alternator, house battery charger, solar panel) but in certain
conditions it could be drawn down and pulling all its charge through
the (8 or 10?) wire from starter batter via isolator and "Max" fuse.
On 8/8/17, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> Out of curiosity, why would you be connecting "fog" lights to the house
> battery? They should be wired so that they operate with the low beam
> headlights. While driving the alternator, not battery should be the power
> source and for lighting especially you want that path to be as resistance
> free as practice. For the house battery, the charge line circuit however you
> did that needs to support charging the battery (20-25 amp) and all those
> connected loads.
> For the lights, especially for DC circuits and lighting wattage ratings are
> nominal. For incandescent bulbs, especially halogens actual current can be
> over a wide range affected by delivered voltage and lamp tolerance. 110
> watts at 12 volts is 9.16 amps. It is counter intuitive but as system
> voltage drop increases (less voltage at lamp) the bulb will run cooler and
> current draw can actually increase. A fuse in its simplest form is a
> resister. It will also introduce a voltage drop. Operation a fuse near its
> full rating will cause it to heat up and can cause nuisance failures. As the
> fuse heats up some of that heat goes to the socket and over time does damage
> there. For the wire from battery to the fuse distribution block an ATO may
> not be the right choice, too much available fault current. Consider a Max or
> as American cars like to use a fuse link. Generally you choose fuse link
> wire one gauge smaller than the wire being protected.
>
> Dennis
>
>
--
Neil n
Blog: Vanagons, Westfalia, general <http://tubaneil.blogspot.ca>
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