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External Power - Wiring

K

kai

Active Member
Hi,

I?m just thinking about how to wire the external power.

One Idea is to install a relay which is powered by the external power and connects the ext power directly to the battery bus. Very simple.

The Other is, to install a second smaller relay, which disconnects the BAT Relay when ext Power is connected. So that the BAT is not connected when ext Power is online. I want to prevent the BAT of any damages (fire...).

How have others done that? Did you install a current limiter, relays, diodes?

Thanks for Ideas,

Kai.
 
Are you looking to recharge or maintain a battery, or you looking to jump start a dead battery.

Wiring and all will be different.

I have a maintain/charge setup, wires go directly to the batteries.

Plug pigtails are in the baggage compartment.
 
The most common certified setup is the flat 3 pin plug with one short pin. The short pin closes a current protected relay directly to the battery after the pos/neg pins are seated. Some cessnas allow power to the bus regardless of master switch position due to where the ext power cables are connected. I'd prefer the connections on the bat side so the bus is isolated unless the master is on. I'm not really advocating the big plug, just 'splainin' it.
 
I put a Piper Power plug on the belly of my planes wired always hot into the on-board battery. Allows for recharging the on-boad battery and/or running the avionics while in the hanger......


kai said:
Hi,

I?m just thinking about how to wire the external power.

One Idea is to install a relay which is powered by the external power and connects the ext power directly to the battery bus. Very simple.

The Other is, to install a second smaller relay, which disconnects the BAT Relay when ext Power is connected. So that the BAT is not connected when ext Power is online. I want to prevent the BAT of any damages (fire...).

How have others done that? Did you install a current limiter, relays, diodes?

Thanks for Ideas,

Kai.
Click to expand...
 
You may wish to reconsider.

A ground power jack appears to be a good idea until you look at the advantages/disadvantages.

Advantages are that you can jump-start your aircraft from a GPU. Don't expect a GPU to charge your main battery, because it's not designed to do so and won't be hooked up for very long.

Jumpstarting your aircraft means that your alternator will be responsible for charging your nearly flat battery, and this is very hard on the alternator.

The GPU may be 28V, which means disaster unless you follow Bob Nuckoll's circuit with overvoltage and polarity protection.

Finally, you are carrying a lot of dead weight around for the occassional non-emergy situation that requires a jump start.

I suggest something similar: a charging jack with a 10 amp current limiter. You can hook up a battery charger to this port (cigar lighter plug for example) and charge your battery properly. In a pinch, you can hook up jumper cables to this port (with an adapter) and a running vehicle that will charge your battery enough in a few minutes to allow a start.

10 amps should be enough to power up some basic avionics for testing if that's what you need to do.

Finally, you can even wire in a small battery charger that runs off of 120VAC and if you have a flat battery, you just need to find a plug in somewhere.

Food for thought.
 
I did just like Mike and Vern. Cig lighter charge ports/power for kids stuff on both main 925 and aux 680 bat. 15A fuse. I use 12A Odyssey chgr. I also connected a spare bat to aux port for avionics setup. I could play for 6-8 hrs on three batteries.

If I run my aux bat down to 11.5 ocv then start with main bat, my alt current goes to 55-60A while powering strobes and recharging batteries. Think what the current would be with a dead battery.
 
Aeroelectric

I installed the Bob Nuckoll's in a recessed box adjacent to my battery (rear-mounted.) It is connected to a self-powered contactor that connects to the main battery contactor and incidentally the battery terminal. The switch/breaker is up front. It is a component of Bob's design. It uses the overvoltage protection to prevent the inevitable 28V SNAFU. An illuminated light lets me know power is connected, whether or not the contactor is closed.

All in all, it took probably 40-60 hours to design, build, and install the recessed box, wiring, etc.

I can hook power to it with no battery and turn everything on, I can jump the plane through it, or I can charge the battery through it.

Was it worth it? Can't say, but it sure is handy. So far about half the people who have seen it say they wish they had something like that. GPU or not, I can jump from any car, which is generally pretty easy to come by. If the battery is dead, just like a car, hook the cables up and leave it for a few minutes. I turn on the EIS and monitor the voltage though.
 
Thanks to all for the Bunch of Ideas, I have to think about every possibility.

Thanks a lot,

kai.
 
Here's my setup

Bob Knuckolls schematic. Hole in the bottom of the fuselage with doubler, mount receptacle from the outside using carriage bolts. Quite low profile all in all. Some day when I run out of things to do, I may fabricate and bond on a little fiberglass fairing. :rolleyes: All of the assembly is shown with the exception of the switchbreaker on the pilot's right hand console, which provides both control and the overvoltage shutdown. Having the battery tray pre-punched to mount the two contactors makes this a natural.

DSC_0052.jpg


DSC_0053.jpg
 
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