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Colyn Case
Joined: 12 Oct 2009
Posts: 13
Location: Thetford Center
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 Posted: Mon Nov 27, 2023 8:29 pm Post subject: Proper ground power plug wiring |
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I have a ground power unit plug wired into my experimental airplane.
It works great but if I leave it plugged in when it’s powered down, it runs the battery down if left in that condition for long periods.
I think I understand what is going on but I’m not sure what to do about it.
The plug is a standard Cessna type 3-pin plug. The little pin closes the relay which connects incoming power directly to the battery.
I think what is going on is that if thes ship’s battery is charged up and the GPU is disconnected from power, the ship’s battery feeds power back through the GPU connection, thereby continuing to power the contactor which connects the GPU to the ship’s battery. This doesn’t use much power but eventually it sucks the ship’s battery entirely dry.
One way to solve this problem would be to put a big fat diode in the path from the GPU to the main battery.
But I was wondering if someone has a more elegant idea.
Colyn Case
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Colyn Case
colyncase@earthlink.net |
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nuckolls.bob(at)aeroelect
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| Posted: Tue Nov 28, 2023 8:49 am Post subject: Proper ground power plug wiring |
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At 10:28 PM 11/27/2023, you wrote:
| Quote: | I have a ground power unit plug wired into my experimental airplane.
It works great but if I leave it plugged in when it’s powered down, it runs the battery down if left in that condition for long periods.
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What is the nature of the GPU? Is it set up for
battery charging/maintenance? Normally this
size connector is intended for ground assisted
starting while being attended by pilot at
controls and GPU operator. It CAN also be use
for charging a dead battery . . . but this is not recommended.
Legacy ground power carts are capable of 1000+
amps of output and are not generally well
maintained for their voltage output setpoint.
Quite often, the ground power operator thinks
if 200A of output is good, 1000A is better . . .
and cranks the knob up.
If you're wanting to connect a microprocessor
controlled, battery charger/maintainer to the
ships battery, I suggest a more pedestrian
approach to hardware. Perhaps a small connector
on a bracket inside the oil-filler door
or some such configuration.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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