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I have the following issue. The essential bus breaker tripped today during flight. The Load dropped down to 3 Amp and Voltage down to 23.2V. Pushing the breaker back in brings the load back to 40 Amp and 27.x Volts. The breaker tripped again and Voltage goes from 24.4V down to 23.2V. The breaker would not stay in.

Any suggestion what this could be? I will bring the plane to the mechanic tomorrow but maybe someone can point me already in the right direction.

Thank you!!
David

Hard to diagnose from just that, but I was told to never reset a breaker in flight, because if it was caused by a short then you were asking for an in-flight fire. That's one of my least favorite things to get when flying, so if a breaker pops in flight it stays popped until I am on the ground.

Good point! I hope the technician can find the problem and fix it. Something always seems to break

Look at the battery first. Given that no other breakers are tripping, that's the likely culprit. Specifically a (possibly high-impedance) short in a single cell could cause this behavior.

Good news I had the plane checked by a mechanic twice and they could not find any issues and the essential bus stopped tripping.

Bad news I still have issues with my Voltage and Hot/Warm Start of my engine. I have a new Batteryminder installed and I am now always charging the battery. They Batteryminder doesnt show any issues with the battery. Just desulfating the battery.

I can cold start the engine without any issues. If I fly for a bit and try to restart the engine warm it does not want to start. It seems like the starter doesn't have enough power to spin the engine fast enough to start. If I hook up a GPU the engine starts up immediately.

The charging Amp in flight is around +11 but now I checked the Voltage after uploading to Cirrusreport. Here are 3 examples of the Voltage.

Any idea what this can be? It seems like the battery is not properly charged during flight.

It looks to me like you should borrow a battery and see if the problem goes away.

Antoine I will try to find a battery I can borrow but I am still curious about the Voltage overview. If the battery is bad I would expect the voltage to go down steadily but the graph shows it jumping all over the place. I am wondering if the alternator or regulator is not working properly or if it is just the battery.

David do you get alternator alerts when on the ground?
When was the last time your alternator's brushes were checked/renewed?

The reason I am thinking of the battery is that it is not keeping its charge in flight - as evidenced by the problematic hot starts.
There may be something bad that causes large current surges (as the alternator pours amps into a defective battery) which could trip the CB.
If it is not the battery, it could be the voltage regulator or the alternator, but I would start with the battery.
Good luck!

I did not get any alternator alerts on the ground or during flight. Also charging Amp is pretty constant during flight. The issues only come up when I try to restart. If I hook up a GPU the engine fires right up.

David,

If all three of your traces are during flight, then you almost certainly have some sort of alternator problem (alternator, alternator brushes, connections to alternator, voltage regulator, etc.). The first trace looks like your battery was charging the first half of the flight, but then stopped mid-flight and you can see the voltage slowly bleed off as the battery discharges. The second graph looks like the alternator was not working most of the trip, but with brief spikes of charging. When the graph is at 28v (looks more like 27.7 on your graph, which seems a little low) your alternator is charging (or trying to charge) the battery. When the voltage is at 24 or 25 and dropping off slowly, your alternator is NOT charging your battery and you are just draining it.

Your story makes sense - the battery minder keeps the battery topped off in your hangar, so your first start is not an issue. But after a flight (with the alternator mostly not charging the battery), there is not enough power left in the battery to turn the starter. Given the behavior of the battery in the graphs you posted, it looks like it is probably ok, but the charging spikes from the alternator are probably not doing it any good!