Cable size for jumper plugs

[CharlieWaffles]

What size cables are people using for their external/ground power jumper plugs to the battery?

[grahamcalder]

no 2

graham

[Mike S]

Are you intending the wiring to handle the load of starting the engine if the battery is dead?

Or, are you only looking to use a charger or maintainer??

Wire size will be driven by the current load needed.

[rleffler]

Originally Posted by Mike S

Are you intending the wiring to handle the load of starting the engine if the battery is dead?

Or, are you only looking to use a charger or maintainer??

Wire size will be driven by the current load needed.

Mike is spot on....

If you want to get an APU from the local APU to get a jump or start in cold weather, then install the larger Cessna type connector and #2awg.

If you just need a trickle charge, then doing something that Paul Dye just documented for his RV-3, works great.

What's your mission requirement? Don't you hate folks that answer a question with a question?

I've got the big Cessna type connector, but haven't installed it yet. I want compatibility with the FBO style APUs, but I really don't want to install that large of a connector. The other item to remember, if you get a jump, who is going to do the disconnect and do you trust them to close up everything? (assuming your in the cockpit of a running aircraft) I was going to install mine in the baggage area, but am rethinking about installing an exterior door.

bob

[JonJay]

"Jumping" the gun here, but if you are planning on a jump plug;
I personally feel that there is little benefit to the external plug for starting purposes. Our relatively small engines are easy to hand prop when cold. (not talking really cold weather, where preheat should be applied anyway, I am talking cold engine, like dead battery overnight engine is not hot)
Also jump or hand starting your airplane due to a dead battery may not get you back in the air. Most systems require some charge on the battery to allow the alt. field to work. Depending on the charging system at hand, you might get an adequate charge in an hour or two, not to start, but to run the alternator.
I would forgo the weight and extra complexity but that is just me.

[flytoboat]

Originally Posted by JonJay

" Our relatively small engines are easy to hand prop when cold.

If you have mags. Electronic Ignitions will require battery power.

[JonJay]

Originally Posted by flytoboat

If you have mags. Electronic Ignitions will require battery power.

You most likely need some battery power as mentioned for the alt. field to work anyway regardless of ignition type. So I don't see the difference.
An external jump plug does not necessarily mean you will be going anywhere even if you get it started, mags or EI.
Don't most EI systems have a back up batt of some sort anyway?

[roee]

Originally Posted by JonJay

You most likely need some battery power as mentioned for the alt. field to work anyway regardless of ignition type. So I don't see the difference.
An external jump plug does not necessarily mean you will be going anywhere even if you get it started, mags or EI.

If you jump start from external power, you can also enable the alternator while still hooked up to external power. The external power source will supply the initial power to the alt field. And then when you remove external power, the alternator can continue to operate, generating power for its own field windings as well as other loads, and charging the battery.

That of course assumes that the battery was just weak or discharged, but undamaged, and will still take a charge. That could occur through a partial discharge through loads left on, self discharge over a long span of time, or even just cold temperature. If that's the case, then with an external power start, you may very well be on your way.

But you're right that there may also be other conditions, like if the battery is damaged or to the point where it will no longer take a charge, where just starting the engine will not solve all your problems. And that's true regardless of the type of ignition system, and regardless of whether you start by hand-propping or with external power.

[rleffler]

[quote=JonJay;590465 Most systems require some charge on the battery to allow the alt. field to work. Depending on the charging system at hand, you might get an adequate charge in an hour or two, not to start, but to run the alternator. I would forgo the weight and extra complexity but that is just me.[/quote]

Very true, but that's why I didn't off a simple answer to the question. It's mission and requirements.

Charlie has a IO-540 which may take a few more amps to get going with cold oil in the winter. With a dead battery and a couple hour charge, you may still want the APU connected through start up. Granted, the shouldn't be a frequent operation or you have other major issues.

In either case, you'll want a common connector that most FBOs can provided. Typicall that will be either the Cessna or Piper style plug. Otherwise you'll have to bring your own conversion cables.

I personally don't like the size and weight of the Cessna connector, but it is the one that is probably most widely availabe if you are stuck someplace away from home.

If you have a VP product, you can take a look at their schematic for a ground plug (regardless of whatever adapter you choose)

bob

[CharlieWaffles]

Thanks for the great info. My ideal is to use it for ground power for avionics work and battery minder work, but if push comes to shove, a jump. I dont like the idea of needing a jump, as if my batteries are that dead, flying is probably not a good idea. I'd rather have a full battery before departing. But there may be a need. So since I want ground power, might as well be able to do a jump. I'm going with a 3 prong style Cessna style and putting it under the baggage floor. So I will go with #2 like I used for my battery cables as well. Thanks, and thanks Bob for the VP schematic, that is exactly what I need as well.