M20F-1968

Ground Power Unit

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M20F-1968    197

I am looking for a Ground Power Unit (GPU) to allow running of avionics, updating software, etc... without running engine.  I have a Battery Minder, but that does not supply enough power.  I am thinking 25 - 50 amps of clean power.  The aviation ones run about $600.00.  There is an automobile company that makes an aviation product (available from Spruce) for about $250.00.  Are there other sources of power supplies that can do the job, but do not have the "aviation" word attached to them that raises the price to 1/2 AMU? 

John Breda

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Yetti    1,306

You can buy the power plug from McMaster.   A couple or one 12Volt auto batteries and a car 12 volt charger should get you going.

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thinwing    566

I have one of these in my shack...it doesn't do 24 v though so I found a 24 v witching power supply on amazon for 90 bucks...puts out max 17 amps which is more than enough

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carusoam    4,005

The trucking industry often uses 24V systems...

The local starting cart has a bunch of deep cycle batteries in it.  Wired specifically for 12V and 24V applications...

PP Thoughts that come to mind....

Best regards,

-a-

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M20F-1968    197

My airplane is a 12 volt system so that makes it easier.

I do not understand the three wire plug going into the airplane.  Pos and Neg DC is obvious.  However, the plug has three wires.  I understand that the third wire somehow activates a solenoid at the battery so the GPU has access to the bus.  Do I have that right?  

The Alinco units look reasonable, but I am not sure I like an adjustable voltage as it give rise to the possibility of error.  

The IOTA DLS-45 has 45 amp, and converts 108-132 AC to 13.4 DC.  It will charge and automatically drop to float charge.  It would be more than enough to do what I want.  

This unit from Spruce http://www.aircraftspruce.com/pages/el/powersupply/portPowerCharger.php  apparently will run the avionics well, but if you want to do anything with audio while on the ground, it inject lots of interference so is not goof for that.

I assume the Alinco units, which are marketed towards the ham radio users, would be better with powering audio and providing clean and controlled current.

Then there is the unknown for me, if I used a unit like the Alinco or IOTA, how is the third pin wired?

Can someone who knows more about this than me chime in?

John Breda

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Jerry 5TJ    742

Third (smaller) pin is + 

I bought a used DIN rail 28V 20 amp power supply off eBay for ~ $30.

IMG_0271.thumb.JPG.496ef41c2356adfaf1c27f1ffb726549.JPG

IMG_0272.thumb.JPG.16f5901a095a8b3d4e3dbc5a13bc3a91.JPG

 Then I got 20' of 8 gauge flexible wire and the standard plug from Aircraft Spruce to mate with the airplane. 

Works ok to run G500 GTN750 etc to upgrade firmware. 

Edited by Jerry 5TJ

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Yetti    1,306

The third pin provides voltage for a solenoid that is on top of the battery box.  The  solinoid activates the power plug.   It is a way to keep the plug from being "live" when the plug is not covering the pins.....

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Bob_Belville    2,786
18 minutes ago, M20F-1968 said:

My airplane is a 12 volt system so that makes it easier.

I do not understand the three wire plug going into the airplane.  Pos and Neg DC is obvious.  However, the plug has three wires.  I understand that the third wire somehow activates a solenoid at the battery so the GPU has access to the bus.  Do I have that right?  

The Alinco units look reasonable, but I am not sure I like an adjustable voltage as it give rise to the possibility of error.  

The IOTA DLS-45 has 45 amp, and converts 108-132 AC to 13.4 DC.  It will charge and automatically drop to float charge.  It would be more than enough to do what I want.  

This unit from Spruce http://www.aircraftspruce.com/pages/el/powersupply/portPowerCharger.php  apparently will run the avionics well, but if you want to do anything with audio while on the ground, it inject lots of interference so is not goof for that.

I assume the Alinco units, which are marketed towards the ham radio users, would be better with powering audio and providing clean and controlled current.

Then there is the unknown for me, if I used a unit like the Alinco or IOTA, how is the third pin wired?

Can someone who knows more about this than me chime in?

John Breda

John, the 3rd pin in the external  power socket does energize a solenoid that closes the circuit of the positive pin to the battery. I use a charger to run avionic and charge the battery if needed. Some charger has a smart feature that prevents the charger from energizing unless it sees a battery which is a catch 22 since the battery is not in the circuit until the 3rd pin sees 12V. 

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N601RX    921
2 hours ago, M20F-1968 said:

My airplane is a 12 volt system so that makes it easier.

I do not understand the three wire plug going into the airplane.  Pos and Neg DC is obvious.  However, the plug has three wires.  I understand that the third wire somehow activates a solenoid at the battery so the GPU has access to the bus.  Do I have that right?  

The Alinco units look reasonable, but I am not sure I like an adjustable voltage as it give rise to the possibility of error.  

The IOTA DLS-45 has 45 amp, and converts 108-132 AC to 13.4 DC.  It will charge and automatically drop to float charge.  It would be more than enough to do what I want.  

This unit from Spruce http://www.aircraftspruce.com/pages/el/powersupply/portPowerCharger.php  apparently will run the avionics well, but if you want to do anything with audio while on the ground, it inject lots of interference so is not goof for that.

I assume the Alinco units, which are marketed towards the ham radio users, would be better with powering audio and providing clean and controlled current.

Then there is the unknown for me, if I used a unit like the Alinco or IOTA, how is the third pin wired?

Can someone who knows more about this than me chime in?

John Breda

There is a switch on the back that disables the adjustment knob on the front and uses a default preset value which you can change. The switch is recessed so it is unlikely to get flipped, but could be covered by some rtv. I have never noticed these causing noise. They spec the ripple at 15mv at full load I believe.  The lighter plug on the front is also nice for powering stuff at home that you would normally have to take out to the car 

Edited by N601RX

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Yetti    1,306

As long as there is a battery in the circuit, It should adsorb most of the noise.

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Piloto    1,303

I have this one from Sears for the last ten years, I think it was about $90. On the maximum amp setting it can delivers 10 amp at 28volts or 200 amps at 14 volts It has wheels for moving it around. Very handy for avionics testing.

José

20170813_155032.jpg

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FBCK    37

I thought and was told these three prong plug where only for starting the engine, when the battery was dead, and would not power the avionics, is this not correct, I can power the plane?

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Danb    1,013

No they have specific units to power the avionics via the plug, mine was just under $400 and I used it quite a bit when learning the g1000

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Yetti    1,306
2 hours ago, FBCK said:

I thought and was told these three prong plug where only for starting the engine, when the battery was dead, and would not power the avionics, is this not correct, I can power the plane?

The people telling you were not correct.

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