Electricity 101 Question

[Timebuilder]

ILLINI-
You have a lot of good information here on elecricity. One additional way to stay safe when jump starting a car or an airplane is to make the positive connection first (think of putting the clamp with the red marking at each end of the cable on the positive terminal of each battery) then attaching the black clamp of one end of the cable to the dead battery, and then finally take the last black clamp at the end of the cable near the "good" battery and instead of connecting it to the negative terminal, connect it to a ground on the vehicle or engine. If you are using a cart full of batteries, this won't be possible unless the negative end of the battery group has been grounded to the cart. If the batteries were grounded to the cart, connect to the cart with the last clamp. This way, you are not near the battery itself if you draw a sprk during the connection process. Take your time and let at least a partial charge build up on the dead battery before you try and start the engine. ALWAYS wear safety glasses when working on or near batteries!

I suspect that the comments about the solenoid being controlled by the plane's battery are correct. In that case, you should charge the plane's battery (having shut off all loads in the airplane, and disconnected the battery gound) so the PT6 generator won't have to try and charge the plane's battery from a very low voltage. It wasn't designed to bring batteries back from the dead. Car owners often make that mistake, especially if they drive a car with the recent design DELCO alternator. They are used in GM cars, and are bedeviled by overheating when worked hard, taking diodes and regulators to the grave.

Of course, they then blame the mechanic.

If you have more questions about electricity, PM me.

 

[prpjt]

Several things were not going your way here. Like Widgit said, if the the aircraft battery indicates less than 20 it must be charged to a value greater than 20V before using auxiliary power. If your aux power start checklist requires you to turn the Battery switch on before connecting external power, you probably have the 20V limitation. You turn the battery switch on to close the the external power relay which allows ground power to flow into the airplane.. Then you leave it on to protect transistorized circuits.
Another thing may have been the polarity of the plug (don't know if it was a standard AN plug) that was running from the golf cart. You probably have a reverse polarity protection in your external power circuitry.
Still another possibility is in the plug if not a standard AN plug, and this sound like a homemade plug, is that the polarity could have been right (Positive lead to center post, negative lead to front post) but the small pin must have a positive 24V to 28V applied to it also.
Lot's of possibilities. Hope your back in the air. My experience is with King Airs, never flown the Caravan, but the Pratt systems could be similar. Just some things to think about.

 

[ILLINI]

Thanks to everyones help and advice, my plane is back up and running strong! I just put the battery back in and got a nice cool start like normal.

 

[bobbysamd]

Battery start

Very interesting discussion.

 

[enigma]

You got a lot of good info, I can't add any to the electron discussio, but I will encourage you to call Maintenance next time.
Or maybe I should say: never ever attempt any kind of maintenance procedure on the machine in which you are about to trust your life; until you are 100% certain that you have a correct and proper procedure.

So next time call maintenance control, or read the AFM.

One last thing. Never attach a GPU to your aircraft until you are certain that it is producing the proper quality of power. A bad, or incorrect, GPU can fry more little black boxes than you can count.

regards