: I decided that I should add some resistance just in case one of the
: batteries (plane or charger) gets really low. I don't want a sudden
: rush through it. Then I realized that if I'm going to do that I might
: as well just use small connectors and wire. And if I'm going to do
: that I don't really need to use the high-power port.

I would think a circuit breaker would be a better idea than a resistor. If
you go through the trouble of making a well-thought-out bypass for the interlocking
mechanism, why limit yourself to a trickle charge?

: Perhaps the answer is to bridge the relay contacts with a low-current
: toggle circuit breaker? That would allow me to easily control whether
: or not trickle charging or discharge can occur through the port but if
: I happen to leave it enabled and a short or reverse polarity condition
: occurs the circuit would be broken.

I think that this could be done well, but I would try to add some interlocking
to the bypass. Probably some diode logic to the coil of a relay. Then you could
protect yourself from reverse polarity on the plug, and overcurrent protect the large
solenoid bypass. Without schematics I can't say for sure the best way, but as I said
before, I'd try to think of every possible failure mode. I'm sure that Piper did.

Along the same lines, I've notice a significant difference in the later
PA-28's from my '69 model. Mine has a 60A breaker in the ALT feed line and the later
ones don't. All I can say is if mine ever tripped, it could put a big load dump
transient on the bus. That could cook a lot of avionics in a hurry.

Be careful,

-Cory


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* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
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