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I am suddenly having trouble with the Jabiru Charging system keeping up with the vary low electrical load in my CH750 STOL. Last week we finished 2.5 hours of flying with stops and engine starts at 5 airports. After fueling up at our home base at the end of the trip the starter struggled a bit to turn the engine over. The voltage on the battery was below 12 volts. I charged the battery with an external charger and then performed a load test on the battery. The battery check out as being in great health which is to be expected with only 70 hours on the aircraft.
1. Any thoughts or experiences from the rest of the Jabiru operators?
2. Does anyone else have the factory installed circuit breaker on one of the leads coming from the alternator?
3. Does the alternator output below seem normal?
Below is a graph of the voltage from the last flight of the day.
That voltage plot looks strange for sure. You should see something more steady and around 14.4 volts. It could be that the regulator is bad. It looks like the regulator fires up the output then quickly shuts it down again. I don't see how the alternator could be at fault here.
I wonder if this could be a wiring problem. If my memory is correct, there is a yellow wire on the regulator. I believe it is the voltage sense wire. The red wire is the one that delivers the charge current to the system. Make sure those two wire are correctly attached.
Don't know if it's related to your problem, but a very common electrical problem with Jabiru's is that the AC voltage wires coming off the PM alternator tend to fry their connectors and either soldering or replacing with aviation-quality connectors is recommended. You might check those connections to see if they look like they've gotten too hot. Also, if the wiring is connected to the regulator with a plastic multi-pin plug, this can sometimes cause problems and Jabiru USA (now Arion Aircraft) used to recommend cutting off the plug connectors, crimp aviation-quality connectors to the wires, and re-connect the wires with a good quality terminal block.
As an update the system keeps the battery charged in cooler weather (80 degrees and below) but not in hot weather. When it is cooler the graph still cycles but the low points are shorter and it keeps the battery charged.
Maybe an electrical engineer type would know, but this reminds me of a graph I saw once showing a circuit breaker cycling. There is now (not sure when it was added) a circuit breaker mounted directly on the engine and before the regulator. It is a standard 12 volt 20 amp automatic reset automotive circuit breaker which seems odd since the stator coil (alternator) would be outputting AC voltage.
So my current (sorry for the pun) theory is the bimetallic circuit breaker is getting hot under the cowling and cycling excessively. It could also be a heat related issue with the regulator, but the circuit breaker is cheap. I found a US replacement for the Australian breaker (made by Busssman) so I am going to try that first. Should be here in a day or so.
There is little danger from operating without the beaker for a quick test flight. I use a fuse in that location. Its simple and has never blown, nor should it ever. If it does I can land, and should land, to deal with it ASAP.
It’s a KABOTA tractor device and I bought on AMAZON.
Hopefully John M got a genuine Kubota regulator - a lot of those sold on Amazon and Ebay are copies. I've had better luck with the genuine Kubota regulator - costs more but lasts longer.