Circuit breaker problems

djbaker · Post by **djbaker** » Fri Oct 21, 2005 11:35 pm

It's been raining in NE for two weeks and the plane has been outdoors at my son's airport. He went to start it today and had a dead battery. Jump started the plane and took off. He expected the generator would bring the battery up. Flew for an hour, landed and when he took off again the circuit breaker for the radio and transponder popped. The wiring is new (2years old) and we have a fairly new voltage regulator. In the air the battery seemed to be taking a deep charge. We tried the circuit breaker on the ground once with the engine running and it popped. We left it popped (afraid of a fire). Any suggestions on where to look?

Sat Oct 22, 2005 12:06 am

Jim

You didn't say whether or not you knew what caused the battery go dead. Like a switch left on.

You also didn't say whether the battery took a charge.

We'll assume the master was off and that cuts the radio circuit from the battery so I'm thinking if you do in fact have a short in that circuit it is another issue and not the cause of the battery being dead.

In less yo know otherwise I'd attack it as two separate problem.

I'd attach a jumper battery or us the aircraft battery if it took a charge. With out the engine running (to eliminate the charging system) and with the radios themselves turned off I'd close the breaker. if it pops there is a shorted wire. If not then turn each radio on one at a time and see which if any fails the breaker. This might pinpoint the problem to just one of the radios. If you can't duplicate the problem I'd suspect water shorting something that as now dried out.

As for the battery. Assuming it's not shot. You didn't say how old it is. If it didn't take a charge and the battery is still capable of excepting a charge, I'd remove it and charge it with a charger. Then when you replace the battery you'll know it has a charge. You didn't say whether you have a generator or alternator but I'll assume you still have a generator. If so you need to flash the regulator after installing the battery in order to assure the polarity of the charging system.

This procedure is simple to do but I don't have it committed to memory. It has been described here on the forum in detail as well as in the 100 serious maintenance manual.

Once your battery and charging system are working correctly you may find your other problem disappears. Can't say why this might happen or even that it should but stranger things have happened.

Anyway the key here is to break it down into the three basic problems, battery, charging system and radio circuit. Then trouble shoot them individually. Perhaps along the way the mystery will reveal itself any you understand if they had anything to do with each other or perhaps not.

Good luck

kloz · Post by **kloz** » Sat Oct 22, 2005 4:19 am

With everything turned off. Take a battery cable loose. lightly touch it to the battery post. If you see sparks you have a drain on the battery, or short in the system. Re-set the breaker and try it again, if it sparks now the short is in the system the breaker serves. Sometimes a really low battery will pop a breaker, as it takes a lot to charge it. Charge the battery with a charger and that should cure the problem.

djbaker · Post by **djbaker** » Sat Oct 22, 2005 11:54 am

Thanks for the info. I knew I'd get good advice here. I'll try the items, one at a time today.

Post by **GAHorn** » Mon Oct 24, 2005 5:23 pm

Kloz, your advice is good advice...for a car. Not for an airplane. The reason is that the car's battery is attached to a "live" electrical system in which most accy's are turned on at the accy with it's power switch...and all those accy's are on ONE electrical buss.
But an airplane (even one as simple as ours) does not have the battery on the electrical buss until the battery relay is closed...usually by turning on the cockpit master switch (which grounds the relay and closes it.) Only THEN is the battery put online at any battery buss.
Complication: If any avionics has a "keep alive" memory circuit, or if there's an electronic clock, etc., which is "hot-wired" to the battery...then connecting/disconnecting the battery cable will also show a current drain. So, while your suggestion is a good, simple, cheap, and quick method to determine if the battery is supplying voltage to a "hot-wired" item... that test may be next-to-useless in this situation, depending upon many other things.
I like Bruce's one-thing-at-a-time approach. (And the way to quickly polarize a gen/reg is: with a fully charged battery already in the airplane, and with the master switch on (but with the engine NOT running) , momentarily connect (flash) the regulator BAT and ARM terminals.)

djbaker · Post by **djbaker** » Mon Oct 24, 2005 6:57 pm

Here is what I did. Took the battery out of the plane and fully charged it. The battery took the charge. Reinstalled battery. Before starting engine, I put on the master and turned on the avionics with the circuit breaker on. Things worked fine, did not pop breaker. Started engine, everything works. The only thing I can figure is that the battery was soo low and the generator was not strong enough to give it a good charge that there was not enough power to run the avionics. Maybe?

Post by **GAHorn** » Mon Oct 24, 2005 7:13 pm

I doubt it.
Keep in mind that a current limiter (fuse or circuit breaker) is intended to protect a wiring circuit.... NOT an appliance.
Your battery is a storage device for electricity. When the source of generated electrical power (your gen or alt) fails, the battery can supply stored electrical power to the electrical system.
However, your avionics sit downstream of the CB you think "popped". In other words the CB is protecting the circuit those avionics are on....not having anything to do with the charging circuit (your batt/gen/regulator).
If one were to look behind the panel, it might surprise you to see just how much un-insulated, live circuitry is open to the air. In other words, a loose/fallen screw, paper-clip, etc. could easily fall across the electrical buss and cause a short. (Most original electrical busses are simple copper strips to which are attached the fuse-holders/CB's.)
It's unlikely that water would pop a CB. But CB's can lose their calibration over time. It 's rare, but it happens. (Most CB's are nothing more than a spring-loaded contact with a bi-metal latch that, when heated by excessive current-flow, simply expands and pushes the latched spring past it's detent thereby "popping" the breaker. A weak/worn latch means lost calibration.) In flight, the standard rule is to reset a breaker only once. Therefore, if more than one appliance is on the "popped" breaker, turn them all off, reset the breaker, and then turn them on slowly, one at a time to restore service. If one of the appliances "pops" the breaker, that's a clue. (But again, keep in mind that fuses/CB's do NOT protect the appliance. They protect the wiring that SERVES the appliance.)

Post by **Bruce Fenstermacher** » Mon Oct 24, 2005 7:36 pm

Jim

Did you polarize your generator after installing the battery? If not and it seems to be charging normal then perhaps it is polarized since the recharge/reinstallation of the battery but wasn't before.

As I said in my earliar post you may never find out what the cause of the breaker pop was. Without a schematic of your exact wiring we really can't figure it out either.

I'd cautiously fly it and monitor things. If the breaker goes again you get the opportunity to trouble shoot as I outlined.

Have you figured out why the battery went dead in the first place? If you know and have rectified that situation I'll bet you have no further problems.