battery charger to get through Piper power port?

: 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


--

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

writes:

: 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.

I really would want a current limiter (not a current killer) in that
situation. I'd still want to charge the battery just not so quickly.

If
you go through the trouble of making a well-thought-out bypass for the interlocking
mechanism, why limit yourself to a trickle charge?

It's all that I need. I have no need for a fast charge and by keeping
it slow I can use the low-power bypass circuit.

: 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.

The circuit breaker should do that. I'm thinking of isolating it from the
relay with diodes but I'm waiting to find my schematics before figuring
out exactly how to do that.

--kyler