"Larry Jaques" wrote in message
...
On Fri, 10 Apr 2015 09:04:36 -0500, Frnak McKenney
wrote:

On Fri, 10 Apr 2015 02:57:10 +0000 (UTC), Ian Malcolm
wrote:
robobass wrote in
:

When the family makes a road trip I bring along a 12v 4 amp
cooler.
The ciggie plug melted long ago and I wired up one of those 3/16"
cannon shaped connectors used for low voltage home stuff like
laptops,
external HDs etc. It also gets very hot and is starting to melt.
What's a good off-the-shelf solution which doesn't take up much
room?
The whole ciggie plug thing is the dumbest convention ever, I
must
say. I can't believe it's still extant.

A good quality cigarette plug connector in a clean good quality
socket
can handle 8 to 10 amps without problems. I have a 100W inverter
that
has one and has never given any trouble. However, it needs to
have a
body that's held together properly with several screws, preferably
a four
sided negative spring contact and a positive contact made out of
plated
machined brass, not pressed steel. If the socket has actually
been used
for a cigarette lighter, its basically trashed by the heat and ash
and
will never be reliable.

Has anyone here used -- or even seen -- a pair of "cigarette
lighter"
plugs wired together and sold as a "jumper cable"? The concept
certainly
has appeal -- battery-to-battery jumper cables are heavy, bulky, and
stiff -- but how would it handle the (say) 100A "cranking current"
needed
to get an automobile with a dead battery started? Ian's "8-10A",
which is
an order of magnitude lower, seems like a good working figure for
that
kind of connection, and with that limitation even a superconducting
cable
wouldn't be enough.

I've seen one. It had 18ga wiring. That's OK for a handful of
amps,
but no more. They only work on low batteries, not dead ones.


Or have I missed something?

Ayup. They're meant to charge the battery, -not- start the car.
Trying to crank over a vehicle with one would likely blow one or
both
fuses for the lighters.

The one I have, likely from Radio Shack, is 16 AWG and 4' long, so
it's more of a lab bench jumper. They sold a series of power supplies
with lighter sockets for outlets. I don't know what they meant it to
deliver power to, but it works well to charge my tractor battery
through the dash outlet I added for the flasher. Cats prowl the place
I store it so I don't like to leave the hood raised and charger wires
clamped on the battery.

-jsw