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Total electrical failure, high amp spikes

B

bermwewjan

Member
Hi everyone,

Experienced a total electrical failure a few weeks ago and the 60A circuit breaker had popped upon inspection on the ground. We're aware that the EarthX turns off below 10.5V or whatever. We haven't been able to replicate the issue, but the flight data for some prior flights show some bizarre spikes in amps (over 300A).

We're running a new B&C LX60, with 60A circuit breaker, and EarthX battery. Any ideas on cause or other things to inspect?

Screenshot 2024-05-19 at 12.25.07 PM.png
 
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I would start with the simplest possibilities. How is your alternator field wire routed? If it's shorting to a hot wire somewhere, that will bypass your voltage regulator. If it's shorted to the B-lead that would cause the alternator to bootstrap itself right up to it's maximum output...
 
Voltage is low, and the low RPM amps seem to reflect full alternator output. The spikes are most likely noise or a loose connection.

Any chance you had to jump start the engine?
Carl
 
Mich48041 said:
Check the screw terminals on the 60 amp breaker. A loose connection can cause heat which can trip a circuit breaker.
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I’m a little suspicious about how the alternator & regulator are actually wired in. B&C alternators are externally regulated and the CB for the regulator (to drive the field) should only be around 7.5 amps. If wired per B&C or Bob Nuckoll’s recommendation, there will be an ANL or similar protection on the B lead. The purpose of that is to protect against a fault on the B lead that would effectively be shorting the battery (source of a LOT of amps). The alternator isn’t physically capable of sourcing much more than its rated output.
 
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bcondrey said:
I’m a little suspicious about how the alternator & regulator are actually wired in. B&C alternators are externally regulated and the CB for the regulator (to drive the field) should only be around 7.5 amps. The shouldn’t be a CB on the B lead…
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Check out Nuckols Z11 for example (attached). The B lead is protected at the firewall, either by a fuse or a CB. This is recommended because the B lead is connected to the battery and if there is a short then 300+ amps will make things mighty hot!
 

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bcondrey said:
I’m a little suspicious about how the alternator & regulator are actually wired in. B&C alternators are externally regulated and the CB for the regulator (to drive the field) should only be around 7.5 amps. The shouldn’t be a CB on the B lead…
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I believe it is 5a…
 
Another big pucture perspective (although it could very well be off base).

1. Looks like you are measuring amps out of the battery.
2. Looks like there MIGHT be some correlation with RPM changes (e.g. vibration).

So ...
Check for loose connections AFT of the battery that have an opportunity to short TEMPORARILY.
 
A 60-amp alternator is not physically capable of putting out 300 amps, no matter what you are doing with the field coil. Either the amperage spike is an instrumentation fault, or you have a short circuit somewhere that is making/breaking and causing that kind of high load momentarily coming out of the battery. The battery is the only device on the airplane capable of putting out that much power.
 
Revisit the Volts1/Amps1 graph and hide Amps1. Does that disclose matching disturbances in Volts1?
I would expect a 300A load to make a noticeable change in Volts1.
 
A 60A CB is too small for a 60A alternator. An EarthX battery demands a lot of current just after start. If you recently switched from AGM to EarthX you could simply be discovering that the 60A CB is too small.

I assume you have a 5A CB for field on the IP.

My preference would be to remove the 60A CB and install a Littelfuse 100A MIDI fuse FWF. Just a few years ago it would have been a Bussmann 60A ANL current limiter. A MIDI fuse is more compact versus an ANL current limiter, 31mm vs 60mm bolt center to bolt center.
 
Going back to the original post and graph, it appears that:
- After startup the alternator was at full ~60amp output. Buss voltage at 13.5vdc also reflects the alternator at full load (I assume normal buss voltage is ~14.2 or so).
- At 00:14 alternator current goes to zero, and buss voltage drops to ~12.8vdc or so . This tells me the alternator is off line (either a bad connection, blown output fuse/breaker, or it failed).
- You went flying with a dead alternator, further discharging the battery.

My guess:
- You started up with the battery at a low charge. The alternator did what it could at idle RPM and when you ran the engine up the alternator put out more - popping the output fuse/breaker.
- The current spikes are noise or arcing and sparking of a loose connection. They do not represent 300 amps spikes out of the alternator.
- If you flew with this plane after the data in the graphs I’d assume the battery was just about flat.
- I ask again, did you jump start this plane? If not was the starter cranking at a slow rate? If either is correct I’d assume starting up with a very low battery charge started the sequence.
- What battery are you using?

Many good comments on proper alternator output fuse sizing. Some things to check. First however I’d pull the battery and put it on an approved charger and see what that tells you.

Carl
 
JohnBright offers good advice. EarthX wants customers to purchase a battery that is capable of accepting the FULL alternator output. Assuming that was done, then the alternator will be putting out more than 60 amps when the battery is discharged and aircraft loads are turned on.
 
Thanks everyone! Truly amazing suggestions and help. We'll check out these potential fixes and report back. I'm hopeful it's a loose connection on the battery.

@Carl Froehlich - we did have to charge the battery (didn't jump it) after the electrical failure as the battery was below the 10.5V minimum for EarthX to even provide power.

@johnbright - looks like the B&C install manual recommends at 70A CP or 60A voltage limiter, so will look at swapping out the CP for 70A. Fwiw, even with a depleted battery, we haven't seen the amperage go above 50 for more than a few minutes during normal ops.
 
bermwewjan said:
Hi everyone,

Experienced a total electrical failure a few weeks ago and the 60A circuit breaker had popped upon inspection on the ground. We're aware that the EarthX turns off below 10.5V or whatever. We haven't been able to replicate the issue, but the flight data for some prior flights show some bizarre spikes in amps (over 300A).

We're running a new B&C LX60, with 60A circuit breaker, and EarthX battery. Any ideas on cause or other things to inspect?

View attachment 63130
Click to expand...
Earth X recommended charging range is 13.9 to 14.7 volts. Looks like you might a tad low. Hopefully you have your Amps 1 red range set to a number that lets you know when you blow a CB. Mine is set at 0 to 3 amps as a red and alert to the CAS. Since I charge (and maintain) at 14.2 volts my red range is 13.2 to 13.7 volts. You should have received an amp alarm and voltage alarm within seconds of a CB opening up. I regularly checking my charging system alarms in flight by turning off my alternators.

Earth X makes a nice battery, but the chemistry (and associated discharge and charge process) needs to be respected. Safe travels!
 
I troubleshot this issue with the OP bermwewjan. While inspecting every wire in the electrical/charging system for security we found that one of the terminals on the 60A CB was snug, but had some very slight movement when pressure was applied. We tightened that wire, and now everything seems to be working normally after several flights, and the data downloads confirm this. We hope this takes care of it. Thanks for all of the thoughtful suggestions. VAF is such a great resource.

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