Ground External Power with G1000

GaryRudolph

GaryRudolph

Filing Flight Plan
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Gary
Just picked up an aircraft with a G1000 and I'm trying to do some training on the ground. I connected a JAC2024H to the external power and when I start the PFD with the Master Battery switch it shows negative AMPS for the M BAT. Is this normal with ground power? Is there a handshake I'm missing?
 
Depends on the airplane in all likelihood. Have your AFM?


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According to the manual on 7-53 it says, if the M BAT ammeter does not show a positive charge, the battery should be serviced before flight.
 
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On my 182, per the service manual, ground power opens a normally closed relay on the electronics side of the bus. I'd have to put power on the battery to mess around with my radios, etc. But I'm a newb, that's my understanding, may be wrong.
 
I'm in a 206, and I thought ground power would open just by connecting it. The POH doesn't have much on it to just run avionics without starting. I'll reread again.

On the ground power it never leaves flood charging mode. The ground power green light is on, but the yellow charging is not.
 
We've had problems with the ground power relay not closing properly. When that happens no ground power is getting to the system. When you turn on the ground power (big red plug in place), you should hear a contactor 'click'.
When in doubt, remove the top cowl and connect directly to the battery. If that shows charging on the G1000, then you need to get the ground power system serviced.
 
Had a shop look at it and the connectors had to be cleaned. It wasn't triggering the relay.
 
I don't mean to hack this thread but I have the same problem. I connected my GPU and turned on my master and Avionics switches and my G1000 is indicating a -11.2 draw. Any suggestions? The instructions on the GPU are very lame so I'm not sure I'm doing the proper procedures to use a GPU. I have a 2007 182T. Thanks
 
I use a Start Pac, but often have to wiggle the plug into the recepticle on my C-182T just right to get the negative current draws to go away.
 
GaryRudolph said:
Just picked up an aircraft with a G1000 and I'm trying to do some training on the ground. I connected a JAC2024H to the external power and when I start the PFD with the Master Battery switch it shows negative AMPS for the M BAT. Is this normal with ground power? Is there a handshake I'm missing?
Click to expand...

You are using a 24-volt power supply, right? 28-volt output? I'm assuming this is a 28-volt airplane.

There's a diode between the third pin (the small pin) and the external power contactor in the Master Control Unit. The external power receptacle is on that box. If the diode is shot, and they do burn out, the contactor doesn't close. Lamar doesn't specify the part number for that diode in any of their literature, and Cessna says it's a vendor item. I had to weasel the part number out of a Lamar engineer. Now, I can't remember what it was, and I'm retired. 1N4007, maybe?
 
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As a followup, the issue is that the Master has to be on to energize the external power relay. Also, the -11 amp discharge is fine as it's measuring the current draw from the external power supply or main battery. It can't differentiate between the two.
 
So if I'm just using my GPU to charge the battery then I would assume that I would need to pull the breakers on the PFD & MFD? And will the GPU charge the standby battery as well as the main?

Actually the MFD would need to have the Avionics switches on so that breaker wouldn't need to be pulled.
 
To be able to charge through the external port you need to do the following.
0. Avionics Bus 1 & 2 off (duh)
1. Master On (to energize the External Power Relay)
2. Pull Essential Bus Breakers (PFD, ADC, Nav 1, Comm 1) as there's no way to turn off the essential bus once the master is on
3. Turn off/down Standby Indicator Lights (instead of pulling the breaker)
4. Arm or keep off Standby Battery depending if you want it to charge* as well

* If you want the Standby battery to be charged as well you need to have it Armed when connected

I'm in the process of installing a Battery Minder lead for the Main Battery as I don't want to pull breakers after every flight to keep the battery maintained. Further, my power supply is not as good at maintaining the battery as the Battery Minder. I'm debating installing a Battery Minder lead for the Standby Battery as well, I'm just confirming in another thread if anyone has done this and where to connect it.
 
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