piclist 2000\03\22\172523a >
Thread: 14V - 12V
face BY : Mark Willis email (remove spam text)

Paul B. Webster VK2BZC wrote:
> Mark Willis wrote:
> > For safety:  fuse the battery, close to the + terminal as you can
> > manage that - Under the 1/4" terminal if you can manage it.
>   Of course, note that this fuse is between the battery and the source
> circuit, while the output circuit, with or without another fuse,
> connects separately and directly to the same battery terminal.
> --
>   Cheers,
>         Paul B.

They can be the same fuse, really - I did neglect to mention the fuse in
the Auto Plug-in connector, though with the existing fuses in the car's
fusebox and the diode & power resistor there as well, that fuse *is*
optional <G>

Power path is Car system - Diode - Resistor - Fuse terminal to battery,
possibly paralleled with a diode - Voltage Regulator to camera;  As most
everything runs off the car battery, the battery's just there to prevent
power dropouts (i.e. when you start the car or if the power connection
falls out of the socket), the battery sits there in "Float" charge
usually, not fast charge, due to the diode drop & resistor.

A second fuse is redundant, really, IMO (so far.)  Maybe you can
convince me, though?  <G>

The idea is to make sure this battery (which is around humans and thus
can have wrenches dropped on it, etc.) doesn't get shorted by accident,
causing burns or other problems.  If you put a fuse holder in line and
then take the fuse holder apart, or remove the fuse entirely, the parts
*can* short to something else or just direct connect to each other,
either causes "Spitzensparken" (in the second case, if something is
across the output leads, even when not plugged in to the car.)  If all
load current's handled by current from the car system, why a second

Also, good idea to make a safe place to store the Auto Plug-In connector
when carrying this rig indoors after use, if you don't store the lot in
the car (we didn't, we dragged it inside & trickle charged it at
night.)  Yeah, the diode "should" protect it from shorting - but not
from being stepped on, which can happen.


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See also: www.piclist.com/techref/power/batterys.htm?key=12v
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Subject (change) 14V - 12V

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