poor mans GPU

WannFly

WannFly

Final Approach
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Priyo
can someone recommend a poor man's Ground Power Unit? the idea is to plug the plane in and push buttons on the ground. I have a battery minder connected, but thats not strong enough to keep the battery charged up for an hour or so.

I have seen people use Stanley car chargers, even in MX shops, so may be that is it. what does POA think?
 
WannFly said:
can someone recommend a poor man's Ground Power Unit?
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Define poor? Do you have an actual EPU/APU/GPU receptacle installed on your aircraft, or are you simply charging on the battery direct? What buttons exactly do you want to push?
 
I use the former battery from my plane and keep it topped off. I then use the battery minder dongle on the plane and the dongle from charging on the spare to connect the two. NOTE: the dongle on the spare just has alligator clips for the battery post, and you MUST put them on opposite so the spare/old battery + is feeding the ship battery + and the 2 - are also connected. I then throw a regular battery charger on the spare to keep things fed and “buffered”.

That’s what I do, but if you’re not comfortable doing it this way, then be very careful.

I suppose you could always connect the charger to ship battery without the spare, but on my 182 I’d have to pull the rear bulkhead to access it. On a plane with easier battery access you wouldn’t have to screw around like I do.
 
My Arrow has a power receptacle on the side and I use a 30 amp Astron power supply with the Piper connector and modified jumper cables to run the aircraft electrical system while I "push buttons" inside. Handy way to check navigator s/w updates and access data from engine monitor, etc. Only when the "master" switch is on will the external supply feed the aircraft bus including charging the ships battery.
 
Bell206 said:
Define poor? Do you have an actual EPU/APU/GPU receptacle installed on your aircraft, or are you simply charging on the battery direct? What buttons exactly do you want to push?
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Battery direct. Playing and learning the new gizmos on the ground is the mission. Don’t have a receptacle, well there is one for jump starting, the stock one from piper , never used it and not sure if that can be used for this purpose
 
Arrow76R said:
My Arrow has a power receptacle on the side and I use a 30 amp Astron power supply with the Piper connector and modified jumper cables to run the aircraft electrical system while I "push buttons" inside. Handy way to check navigator s/w updates and access data from engine monitor, etc. Only when the "master" switch is on will the external supply feed the aircraft bus including charging the ships battery.
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Yupp, I have that receptacle too, sounds like I can just use that. Could you elaborate more on your set up?
 
455 Bravo Uniform said:
I use the former battery from my plane and keep it topped off. I then use the battery minder dongle on the plane and the dongle from charging on the spare to connect the two. NOTE: the dongle on the spare just has alligator clips for the battery post, and you MUST put them on opposite so the spare/old battery + is feeding the ship battery + and the 2 - are also connected. I then throw a regular battery charger on the spare to keep things fed and “buffered”.

That’s what I do, but if you’re not comfortable doing it this way, then be very careful.

I suppose you could always connect the charger to ship battery without the spare, but on my 182 I’d have to pull the rear bulkhead to access it. On a plane with easier battery access you wouldn’t have to screw around like I do.
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I have a easy access to the battery, I think I am gonna skip this, but I do have a spare old aircraft battery, so definitely some food for thought
 
WannFly said:
well there is one for jump starting, the stock one from piper , never used it and not sure if that can be used for this purpose
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FWIW: As mentioned above, this would be the preferred way to power up your elec system vs using just a charger/battery direct. You could either buy a power supply or build a battery cart to provide the external power.
 
Just build your own, it's so easy. Get a commercial power supply($50) 3d printer($300) some various other parts and tada, power supply:

moo17.jpg
 
Be cautious of using any no-name CHICOM junk power supplies. If you ever get bored test some of your wall-wart DC supplies and check how accurate the output voltage is versus what is listed on the label. I think you’ll be surprised.
 
I wanted the same, for the same reason. I ended up using the GTN iPad simulator app, as it did 90% of what was hard to learn. It does way more in the app than sitting in the plane. The other reason I bagged the idea was connecting power was not easy. The power port in my 73 Challenger/Archer doesn't power the Avionics Buss. No easy access to the battery for direct connection.

You can "fly" in the iPad app, so setting up approaches etc. is pretty real. My IFR instructor also was VERY familiar with my GTN and G500. He showed me shortcuts and capabilities I didn't know it had. I think you said you were going for your IFR, make sure that's part of your criteria for selecting him/her.
 
YooperMooney said:
Be cautious of using any no-name CHICOM junk power supplies. If you ever get bored test some of your wall-wart DC supplies and check how accurate the output voltage is versus what is listed on the label. I think you’ll be surprised.
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Yea, I forgot that part, you also need a $300 timey voltage graphy thingy... I think this was at about 20A load(50% of rated)
moo18.jpg
 
Hang 4 said:
I wanted the same, for the same reason. I ended up using the GTN iPad simulator app, as it did 90% of what was hard to learn. It does way more in the app than sitting in the plane. The other reason I bagged the idea was connecting power was not easy. The power port in my 73 Challenger/Archer doesn't power the Avionics Buss. No easy access to the battery for direct connection.

You can "fly" in the iPad app, so setting up approaches etc. is pretty real. My IFR instructor also was VERY familiar with my GTN and G500. He showed me shortcuts and capabilities I didn't know it had. I think you said you were going for your IFR, make sure that's part of your criteria for selecting him/her.
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I used the iPad app and got bored in like 10 mins. Very good point on the power port, I don’t know if it actually powers the avionics bus or not. Re: IFR, yeah my II already flies with dual 750 and now a GFC 600 AP. As much as I want to get the very done ASAP, I might have to take a pause due to the COVID
 
Wannfly...I modified a standard set of jumper cables by cutting off both ends, installing the Piper "pin" plug on one end of the 2-wire cable and "ring" connectors on the other end that are attached to the 30 amp power supply. That's all there is to it. When you connect the cable to the Piper external jack nothing happens until you turn the "battery" master switch on. At that time a solenoid closes the circuit from the external jack to the aircraft bus thus powering everything in the airplane. So you can run the avionics as long as you please without running the ship's battery down.
 
Arrow76R said:
Wannfly...I modified a standard set of jumper cables by cutting off both ends, installing the Piper "pin" plug on one end of the 2-wire cable and "ring" connectors on the other end that are attached to the 30 amp power supply. That's all there is to it. When you connect the cable to the Piper external jack nothing happens until you turn the "battery" master switch on. At that time a solenoid closes the circuit from the external jack to the aircraft bus thus powering everything in the airplane. So you can run the avionics as long as you please without running the ship's battery down.
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Awesome, thanks for the pirep, I am gonna try this out
 
Arrow76R said:
My Arrow has a power receptacle on the side and I use a 30 amp Astron power supply with the Piper connector and modified jumper cables to run the aircraft electrical system while I "push buttons" inside.
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Astron makes a great unit. I have a 30 amp regulated supply (not an Astron) that I use in the ham radio shack. It has been used to power the aircraft when needed. My aircraft is experimental so the connections are not what you'd have. But for my purposes the 30 amp regulated supply is enough for most any button pushing I might want to do.
 
There's a guy on COPA that makes exactly this, think I paid about $150, brand new, including the cable and connector, good looking unit, plug and play. Makes several capacities to choose from.
 
YooperMooney said:
Be cautious of using any no-name CHICOM junk power supplies. If you ever get bored test some of your wall-wart DC supplies and check how accurate the output voltage is versus what is listed on the label. I think you’ll be surprised.
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for even more fun, put them on a scope and see how much ac they put out.
 
WannFly said:
i decided to go with the plug and play version

Schauer 12v 25 Amp Piper Aircraft Power Supply & Smart Battery Charger. Chief is selling it for $234 https://www.chiefaircraft.com/sch-jac2512p.html

thanks all and especially @Rob58 for pointing this out
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I have the same one. You will like it. I spent hours and hours learning all my systems when I first got my 182. I also played with the GTN750 app from Garmin but nothing like sitting in the plane and figureing it all out. It also comes in handy if you just want to update your charts and don't plan to fly.
 
AlphaMike said:
I have the same one. You will like it. I spent hours and hours learning all my systems when I first got my 182. I also played with the GTN750 app from Garmin but nothing like sitting in the plane and figureing it all out. It also comes in handy if you just want to update your charts and don't plan to fly.
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Question for you: did you use the external power port on the left side of the front cowl on your 182 to hook up to? If so, what year model?
 
455 Bravo Uniform said:
Question for you: did you use the external power port on the left side of the front cowl on your 182 to hook up to? If so, what year model?
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The power port on my P model (1973) dosent seem to be connected to anything but the starter. Even with the mater switches on I did not see the voltage. (the plane is new to me so this could be a problem with the port or someting) My battory is easy to get to so I just connect straight to it with the alligator clips.
 
AlphaMike said:
The power port on my P model (1973) dosent seem to be connected to anything but the starter. Even with the mater switches on I did not see the voltage. (the plane is new to me so this could be a problem with the port or someting) My battory is easy to get to so I just connect straight to it with the alligator clips.
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Gotcha. That’s why I asked. I have a ‘76 P. There is a solenoid in there that disconnects most of the electrical system (avionics) but the starter system. There may be a mod for that to tie the avionics buss into the power port which I can’t remember.
 
The 141 school I learned at had one. It was little more than a homemade cart with a couple of deep cycle batteries and a GPU plug. I think they had it set up for either 12 or 24v. The thing looked rather rough, but it was enough to start a plane when someone left the master on or the like.

A lot of planes (including mine) have the GPU plug after the battery contactor. Neither master switch affects it. Further, since the battery contactor is powered by the battery, if the battery really dead, jumping it off ground power won't result in it closing and allowing the battery to charge.

I was considering adding a momentary switch and fuse to allow me to jump the contactor coil from the gpu side. That way if I jumped the plane, I could just reach back and push the button and close the contactor.

The sad truth is that it's so easy to get to the battery (it's just inside the baggage door behind the wing) that it's easier to just jump the thing with regular jumper cables (12V as well).
 
I keep mine on a 25 dollar motorcycle battery tender. I've spooled the electrics up while plugged in and not had an issue. My batteries last a long time, too.
 
alright so i got the APU and it works, however, I noticed a dew things that require further clarifications as to why it is behaving the way it is. The APU is connected to the external plug, PA-28-181

What I noticed is, when the master (both Alternator master and battery master on the split switch) is ON, the external power is not being used, it is plugged in but the draw is from the battery. If the both master is off and I turn on the avionics master, it uses the external power. What I am wondering is if when turning the alternator master on, it is bypassing something? Here is the electrical diagram that I have no idea how to read

What i am going to try is just using the battery master ON, APU plugged in and see if the APU is charging the battery or not. the APU can also be used to charge the battery when i am not flying, but i cant tell if it will charge the battery at all.

upload_2020-6-3_15-9-32.png
 
WannFly said:
Here is the electrical diagram that I have no idea how to read
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Is your BAT/ALT switch a true split switch where each side moves separate? Per your diagram below, when you plug in your APU power flows via the red line and powers what I think is the main buss. So when you turn on your avionics switch it should get its power from that main buss. But when you turn on the battery master you now have power flowing from the battery (blue line) along with the APU power. Considering your APU only puts out 25 amps and your battery has more available amps (potential), the battery usually will "out-power" the APU and power the buss.

As your APU does have a smart charger built in it should charge your battery with the BAT switch ON. However, it would be preferred to pull the 70A CB that powers the main buss to try and isolate the charging voltage to the smallest circuit area possible.
upload_2020-6-3_19-28-13.jpeg
 
If your battery is completely dead, the BATTERY CONTACTOR will NEVER close and there is no way the battery ever gets into the circuit (had apparently the clock and the Hobbs meter won't run either).
 
Bell206 said:
Is your BAT/ALT switch a true split switch where each side moves separate? Per your diagram below, when you plug in your APU power flows via the red line and powers what I think is the main buss. So when you turn on your avionics switch it should get its power from that main buss. But when you turn on the battery master you now have power flowing from the battery (blue line) along with the APU power. Considering your APU only puts out 25 amps and your battery has more available amps (potential), the battery usually will "out-power" the APU and power the buss.

As your APU does have a smart charger built in it should charge your battery with the BAT switch ON. However, it would be preferred to pull the 70A CB that powers the main buss to try and isolate the charging voltage to the smallest circuit area possible.
View attachment 86366
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Yes it is a true split switch, well, i can just turn on the battery side of the master, when i turn the alternator side of the master, both switches turn on simultaneously. I will give it a shot again in a day or two. I was supposed to do it yesterday... but it was too nice of a evening to play in the hangar
 
Again, if the battery is completely flat, it doesn't matter what you do with the switches, the alternator, or the GPU. The battery contactor will not close and the battery will NOT be in the circuit (and hence remain dead). Another thing to note is that if you plug in the GPU, everything will be powered (it doesn't need either side of the master to be on). This can cause some amount of surprise at times.
 
flyingron said:
Again, if the battery is completely flat, it doesn't matter what you do with the switches,
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Don't know what this has to do with the OP in powering his avionics on the ground and keeping his battery charged with an APU? But lots of aircraft are wired similar where a low/dead battery will not latch a battery relay. So one either charges the battery or manually latches the battery relay with charging power applied.
 
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battery is not even close to being dead.

went the hangar last evening and played with the APU some more.

APU Connected >> Battery side of the master ON - APU charges the battery - this is probably what i will stick to while playing with avionics

Turn both master off, there is still power in the bus (G5's running and not on battery power), battery is still charging.

@Bell206 and @Sinistar - Thanks for the diagram and explanation
 
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