External Power Plug

[pkofman]

My mooney has an external power plug. Just wondering if   it is appropriate to leave the plane plugged in through the External Power when not flying

Does it trickle charge the batteries, or is only to be used  when the master is on ( on the ground )without the engine started so as not to run down the battery

Peter

Edited January 16, 2017 by pkofman
spelling

[carusoam]

It is a real challenge to use the external plug for battery maintenance.  There is a solenoid that needs to be kept on. This solenoid is there to provide a safety to prevent line personel from hooking up a battery cart that is reverse polarized.  The solenoid interferes with some smart battery chargers that sense the status of the battery before sending any voltage.

Most people have gone to battery minders that are wired separately.  A plug for the float charger is often put in the O2 door (or similar) for easy access...

Best regards,

-a-

Edited January 16, 2017 by carusoam

[Yetti]

There are three pins.   One of the pins fires the relay.   Most chargers won't  fire the solenoid. You can get the plug at mcmaster carr.  You could have another battery that is hooked up to a charger and plug that into the plane.

[pkofman]

You guys are way ahead of me.. My question was pretty simple. Can I leave the plane plugged in , in order to keep the batteries alive in the cold.

I think i misunderstand the entire purpose of the external power thingy

We used it recently when in the hangar whilst checking avionics.

Perhaps it is just for temp use so that we dont run down the bat's when the engine is not running

Peter

[carusoam]

Generally you could, but it probably won't work using the external plug...

1) The safety solenoid needs to be kept alive, it requires power.

2) an external battery can do this.  But, now your system may be charging two batteries at the same time... or three in a LB...

3) If the charger senses the battery to be full and shuts off, what happens next?

4) the solenoid that is keeping the system alive starts draining the battery you are trying to keep charging...

5) the external plug is a good way to jumpstart the engine with a weak battery, but not much more than that...

6) solenoids have a tendency to wear out.

I put this in the ideas that are too complex to be useable box... the battery minder people have made a system that can handle two batteries like a LB has.  It is specific to the type and manufacturer of the batteries being used. Trying to use the external plug with a solenoid adds to the challenge.  

I'm a bit fuzzy about keeping a solenoid alive continuously that is designed or selected to be hooked up for a brief period of time.

7) So what you simply want to do is get the battery minder for your battery system and have the tiny plug brought out to an easy to access spot.  This does what you want with no extra Engineering for things you don't want...

Best regard,

-a-

 

Edited January 16, 2017 by carusoam

[StevenL757]

Peter, from a "best/recommended practices" standpoint, I wouldn't leave a generic external power supply plugged in full-time.  Flying the airplane once per week (maybe once every two weeks, max) eliminates the need to use any sort of external PS, but for those who can't fly this often, a battery minder is usually the way to go to safely maintain proper charging.  Plenty of postings here from those who have them, and good reading.  

A simple external power supply - like those used to check/train with avionics - aren't designed to keep your batteries charged whilst protecting the expensive relays (four installed in the Ovation at $400+ each) and the batteries themselves.

Does this help?

[pkofman]

23 minutes ago, StevenL757 said:

Peter, from a "best/recommended practices" standpoint, I wouldn't leave a generic external power supply plugged in full-time.  Flying the airplane once per week (maybe once every two weeks, max) eliminates the need to use any sort of external PS, but for those who can't fly this often, a battery minder is usually the way to go to safely maintain proper charging.  Plenty of postings here from those who have them, and good reading.  

A simple external power supply - like those used to check/train with avionics - aren't designed to keep your batteries charged whilst protecting the expensive relays (four installed in the Ovation at $400+ each) and the batteries themselves.

Does this help?

Yes excellent and I'll check the other posts. Very helpful 

[dcastor]

I will just add that the third plub

22 hours ago, carusoam said:

 This solenoid is there to provide a safety to prevent line personel from hooking up a battery cart that is reverse polarized.

-a-

 

I don't think that's exactly why the relay and third pin is there, although you are right it would prevent reverse polarity too.  The third pin is shorter, so it doesn't trigger the relay until the other two pins (+ and -) are already making contact.  So, I think the main reason for this is to prevent arcing.

The reason I think this is if that's the main goal, it would be far simpler to use plugs that only go in one way, which is accomplished by this 3-pin plug.  I'll admit that I've seen versions of this plug with jumper cables connected to it, which would be really easy to screw up...so it could be the engineer was looking for a fool-proof solution.

Dave

 

 

[Bob_Belville]

The circuit from "+" pin of the receptacle to the battery is not closed unless there is power to the third pin which closes the relay. The power comes from a jumper from the "+" pin. I have a couple of battery chargers, the brand new one is too smart - the "+" jumper wire is not hot unless it "sees" a battery connected so it doesn't supply the power to make the relay. The dumber charger works fine.  

[blaine beaven]

My 12v power port on my dash is always hot - I use a small battery minder (1a smart kind) plugged into that port to keep the battery warm/charged in the winter. I've forgotten the master on, which drained the battery completely, and this was able to bring the battery back after leaving it charge for a few days.

Sent from my iPhone using Tapatalk

[thinwing]

I might be wrong but I thought the ground power plug is like a 2nd battery and is directly wired to main aircraft bus...plugging power in is equivalent to switching master power on but power is coming from power supply or ground start batteries on the cart.I think their might be a trickle charger from this plug to the aircraft battery but as pointed out the typical Cessna style 3 pin plugs contains 2 positive and 1 negative contact in order to power solonoid.These are typically heavy gauge cables to handle 100 amps and up

[ArtVandelay]

This is how my J is wired, it connects to the battery before the master switch...

 

[thinwing]

27 minutes ago, teejayevans said:

This is how my J is wired, it connects to the battery before the master switch...

 

Doesn't that circuit show the plug power bypassing the battery altogether and going to the starter solonoid?

[mooniac15u]

5 minutes ago, thinwing said:

Doesn't that circuit show the plug power bypassing the battery altogether and going to the starter solonoid?

It goes through the external power relay and connects to the battery side of the master relay.

[thinwing]

9 minutes ago, Hyett6420 said:

Since ive got one as well, can i jump in.  Can you plug a cart to it just to power the avionics while you,"play" the functions, or does this damage the electronic bits of the aircraft.  I know it is principally for starting the engine in case of a flat, i just womdered if it could be used for a short while (hour or so) for the above use?

Yes...I am currently building a ground power setup using a 24 v 15 amp switching transformer cabled to an aircraft spruce Cessna 3 pin plug.I have been playing with the new avadynes and current draw is 11 amps with everything on.Thats about an hour of use which goes by fast...oh transformer is 110 v to 24 mean well sp-500-24 20 amp 480 watts 150 usd.They make 12 v models.

[thinwing]

I got mine from amazon

[mooniac15u]

16 minutes ago, Hyett6420 said:

Since ive got one as well, can i jump in.  Can you plug a cart to it just to power the avionics while you,"play" the functions, or does this damage the electronic bits of the aircraft.  I know it is principally for starting the engine in case of a flat, i just womdered if it could be used for a short while (hour or so) for the above use?

I use it to power the aircraft if I'm working with the avionics or testing the landing gear.  Just be careful; not all power supplies are the same.  Some have a jumpstart mode with a high amperage.  I don't think that's good for the battery.

[carusoam]

The cart should work pretty well.  The relay will allow the power to flow.  Use caution...

Not something to leave on permanently because there is wear involved and the opportunity to overcharge or overheat the system.

The voltage difference between the cart and the ship's battery will probably try to charge the battery.  A way to check on this is to note the ship's voltage before and after the cart being attached.

I get the feeling the cart and ship's battery may have no limits to transferring electrons.  A difference in charge could cause a large flow of electrons from one system to the other...

The battery minders with their tiny brains and current limits seem to be the best way to handle this task.

PP with excessive battery expenses thoughts, not a mechanic or avionics guy...

Best regards,

-a-

Edited January 26, 2017 by carusoam

[thinwing]

I set the voltage on transformer to 26 v which is the open circuit voltage of a fully charged Concorde agl 24 v battery.

[Bob_Belville]

I am experiencing a problem. The solenoid remains closed after I pull the plug.Apparently there needs to be a diode in the circuit. Advice? Manuel lists two but not clear. The used system I bought did not have a diode.

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[Zaford]

 
 
 
AN2551 The purpose of the 3 pin ground power unit connector
 
The purpose of the 3 pin ground power unit connector in aircraft ?
Why the third pin is shorter in length than the other two and is its Purpose.
The smallest pin is limited to 100 W.
There are two larger pins that carry DC power and one shorter pin.
It allows the device to be plugged in, the power connections made, and then the power turned on as the connector is inserted.
It also allows the power to be disconnected prior to the larger power pins clearing the connector. The shorter smaller positive pin, does a few things:
1. It removes ignition sources such as sparks when connected or disconnected from receptacle.
2. Connection is made before power is supplied.
3. Increases the reliability of the connectors.
4. The connectors are not powered at all times. (the solenoid pin can control the power management).
5. A power limited switch can be installed, or split pen.
6. It makes a polarity protection.
The terminology is sometimes called "hot-swap". because power is disconnected during the removal process. No sparks fly in the process and no connectors are damaged.
Typically 3 pin aircraft ground power connectors use two circuits to prevent arcing when the pins are plugged into the sockets.
Two larger pins provide power and ground for the main high voltage circuit. The shorter third pin powers a low amperage circuit that energises a solenoid to close the high amperage circuit after the longer pins have first been partially inserted into their sockets. The low amperage circuit makes use of the aicraft electrical systems common ground and therefore needs only one pin for power.
  

[carusoam]

Welcome aboard, Zaford.

Any thoughts on the 100w circuit and the longevity of the relay?

Somebody mentioned leaving things plugged in through this plug for extended periods of time.  This may leave the third pin activated for days on end...

Best regards,

-a-