alternator / electrical acting up…

[dominikos]

you guys are my go to for brainstorming options… here is a real-time ask for feedback. 

On a flight back home from the bahamas (1000 NM so far), 200 miles from home, the alternator/battery or electrical started to act up. I took decision to land in Baton Rouge. The question is what to do next. 

Here is what happened, after 8+ hours of flying in a pretty warm weather (last leg at 3,500 VFR to avoid IFR headaches), the EMS started to show negative current - picture 1. 

The battery voltage started to drop off (got down from usual 13.6 to 12.2). Made decision to cut this leg short and land in Baton Rouge. Weekend, so no mechanic on the field to be found). For a peace of mind, went back to start engine and things looked actually normal, okay 2nd picture shows Amps going way high but then back lower, potentially explained by battery needing charging.

Here are my options, I think there are two:

• wait for A&P to show up on the field on Monday
• do some more troubleshooting tomorrow morning - make sure that run another test tomorrow morning hoping that the primary issue was with overheated engine compartment (low altitude flight in last leg). If looks good, do a flight in a pattern. If looks good, go home, be conservative on electronics. turn off 2nd nav/com, AP, etc. Skyview has hour+ battery so its backup. What would really suck is to do manual gear extension and no flap landing. 

What do you guys think? Family is heading home on a commercial flight mid day, so, the pressure (and stress in cockpit) is going down.

Thanks, Dominik

 

[Ragsf15e]

No pictures yet, but sounds like the alternator stopped producing power for some reason, could be alternator, Voltage regulator, or any of the wiring between the busses and those parts.  The discharge you mentioned is what happens when the battery is no longer being charged.  That’s a normal indication with the alternator not on line.  The high amp reading later when it was working is normal for a battery that is in need of a charge.  
 

Couple thoughts, is 13.6v really your normal?  That’s low.  Should be 14.0 +\-0.1.  Likely you have some issues even when it’s working right?  Which VR do you have?

I would definitely stay vfr and have a backup plan (gear? radios, etc), but if you start it and it’s working, I probably wouldn’t hand an intermittent electrical problem to a mechanic away from home that he can’t even duplicate. 
 

The normal issues are busted field wire connections at the alternator, and those are easy to check.  Wiggle them see if they’re loose.  Maybe the VR over voltage protection? Depending on which vr you have.

After you’re home, I’d work on cleaning up the electrical system because 13.6v says there’s likely an issue brewing.

[Ragsf15e]

Any way to look back at engine data and make sure the amps were low before the alternator went off line?  During normal cruise with a healthy battery you might see like 4. In the bottom 2 pictures, with the alternator working, You’re showing ~30 which is probably just charging your mostly dead battery, but was it a normal number before the failure?

[Ragsf15e]

@PT20J this is his wheelhouse. 

[dominikos]

this is completely random sample, April 30th. Typical current, 13.5V, 4A.

 

[Ragsf15e]

7 minutes ago, dominikos said:

this is completely random sample, April 30th. Typical current, 13.5V, 4A.

 

Yeah that’s normal amperage, low voltage.  I would definitely start troubleshooting the low voltage (at home).  Low voltage but charging isn’t going to break anything, but it’s not right and not good for the long run health of the battery.

[PT20J]

The first picture looks pretty standard for the alternator being offline: Ammeter showing a discharge and battery voltage decreasing as the battery discharges. 

The second picture looks like the alternator is working. The voltage is a bit low as @Ragsf15e noted, but the current seems really high. Even with a discharged battery, I wouldn't expect 39 amps. There are lots of possibilities. Always check the easiest things first, like all the connections to the alternator and the ALT and Master switch. Also, I assume that no circuit breakers have popped.

The fact that it quit charging and then started charging again after shut down and restart might mean that the over voltage protection circuit tripped. Turning off power to the regulator resets the OVP. The high charging current might be due to a bad cell in the battery. How old is the battery? The 4A charge in the last picture seems high (assuming that this is after half an hour or so in flight after start and that the ammeter is correctly calibrated and the shunt installed correctly). After an initial higher charge rate to replenish the battery after a start, the ammeter should read near zero since the alternator is supplying current to the load and the battery is just trickle charging. I might have the battery capacity checked.

Skip

[Marauder]

If you have the ability to check the history of the voltage, I’d look for periodic drop off from the 13.8v on the last flight and a couple of the previous flights. When my voltage regulator failed, it would periodically drop low (13.1 to 13.3 range) and then pop back up to 13.8v. It may be that the regulator has been dying and you didn’t see the intermittent drop offs. I did notice mine on the flight it failed but it would pop back up to 13.8v before dropping to 12.8. Upon restart it went back up to 13.8.

The 39 amp draw is unusual. It could be as PT stated that it is trying to charge a defective battery. Again, I’d look at the history of the amperage over the past few flights.


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[Ragsf15e]

10 hours ago, PT20J said:

The first picture looks pretty standard for the alternator being offline: Ammeter showing a discharge and battery voltage decreasing as the battery discharges. 

The second picture looks like the alternator is working. The voltage is a bit low as @Ragsf15e noted, but the current seems really high. Even with a discharged battery, I wouldn't expect 39 amps. There are lots of possibilities. Always check the easiest things first, like all the connections to the alternator and the ALT and Master switch. Also, I assume that no circuit breakers have popped.

The fact that it quit charging and then started charging again after shut down and restart might mean that the over voltage protection circuit tripped. Turning off power to the regulator resets the OVP. The high charging current might be due to a bad cell in the battery. How old is the battery? The 4A charge in the last picture seems high (assuming that this is after half an hour or so in flight after start and that the ammeter is correctly calibrated and the shunt installed correctly). After an initial higher charge rate to replenish the battery after a start, the ammeter should read near zero since the alternator is supplying current to the load and the battery is just trickle charging. I might have the battery capacity checked.

Skip

My normal amp reading with a good battery is around 4amps too.  Do you think there’s an issue there or could that be a difference between your 28v system and our 14v?

[kortopates]

You definitely lost your alternator. Re-starting re-set it. If it happens again, pull and reset the field breaker to reset it.  It may never happen again for  along time or you may have a real issue still lurking. 

But don't take off till your battery is fully charged back up, if not already. You were partially doing that on the ground with alternator, but much better for your alternator to do with a charger instead.

 

[N201MKTurbo]

The fact that it started working again would make me suspect the regulator. Did you power cycle the regulator when it went off line? I’ve found that often gets it going again.

[dominikos]

47 minutes ago, N201MKTurbo said:

The fact that it started working again would make me suspect the regulator. Did you power cycle the regulator when it went off line? I’ve found that often gets it going again.

I didn’t. Looking back, it was a miss on my part. But I was close to Baton Rouge so it was an easy call to land. Also wife would freak out if I started to look through emergency procedures. Nevertheless, miss on my end as I should have thought of this first.

[dominikos]

Problem solved, there was a wire that slipped out from its crimp - see area circled in red on the first picture. 
second shows test run, battery charging and the amps started to drop as the battery charged. And my face grinning in reflection.

 

big thanks to everyone who pitched in, it was great to have the moral support from you guys as I worked through the issue.

[PT20J]

3 hours ago, Ragsf15e said:

My normal amp reading with a good battery is around 4amps too.  Do you think there’s an issue there or could that be a difference between your 28v system and our 14v?

Maybe. The current should be about half for a 28V system. I put in a new battery when I installed the G3X/EIS. Mine goes to zero during cruise.

Anyone else what to share cruise ammeter and voltmeter readings for their 14V system?

[EricJ]

5 minutes ago, PT20J said:

Maybe. The current should be about half for a 28V system. I put in a new battery when I installed the G3X/EIS. Mine goes to zero during cruise.

Anyone else what to share cruise ammeter and voltmeter readings for their 14V system?

14V, 2 A.    

[David Lloyd]

Unlike the old analog amp meter in my airplane that only shows a battery charging or discharging, the Dynon could be installed in one of several configurations. It appears to have been installed in this case, to show the current going to or from the battery.  With the alternator operating properly and a charged battery, the display should show one or two amps, just maintaining the battery.

After starting the engine, the amp reading would be considerably higher for a short time as the battery is recovering from the high amp draw start.  A minute or so, it should be less than 10 amps, within 10 minutes it should be back to normal, one or two amps.  Something similar for the alternator being off for whatever reason and then on again.

If the alternator goes off line in flight, the total amp draw from the battery will be seen. Two or three amps for the Dynon display, another amp for the transponder and ADSB receiver, another three or four for the GPS/navcom and audio panel.  Strobes? Nav lights are about 10.  An old GE light bulb or pitot heat really runs up the amp bill.

The voltage looks in line for what the book says, 13.6-14.8 volts at 80*F.  That's a pretty generous range.  14.8 seems high but that's what the book says.  My adjustable voltage regulator is set to 13.9.  

Without your wife in the plane, pull the alternator field breaker and study what the voltage and amps show.  How much load can you shed?  Can you fly 30 minutes on battery and do an ILS and still power the gear down?  No problem?  What if the nav lights and strobe were left on?  It is a lot better to find this out on a nice day.

Another thought: 4 Amps charge to a good battery might include a couple amps to power a Surefly ignition hardwired to the battery.

[Marauder]

I think he has it set up like David mentioned as a load meter, not as an charge/discharge ammeter. Even the JPI 900/930 can be set up this way.




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[dominikos]

In flight, it was a steady, 13.8/V2A

[Ragsf15e]

1 hour ago, Marauder said:

I think he has it set up like David mentioned as a load meter, not as an charge/discharge ammeter. Even the JPI 900/930 can be set up this way.




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I think the one’s above are like mine (edm930) and most (all?) Mooneys came this way… with alternator working, it’s only showing amps to charge the battery - not total load.  Should be only a couple amps (although mine is ~4).

Without the alternator, it shows amps from the battery which is total load since the alternator is off.

I bet you’re right about the edm having the ability to be set either way though.  I fly a piper that shows total load all the time.

 

[BaldEagle]

1 hour ago, dominikos said:

In flight, it was a steady, 13.8/V2A

For additional piece of mind, I took my ‘78 J for a test flight yesterday after reinstalling a repaired alternator: my JPI was showing 14 volts while the battery was being topped off and then settled back to 13.8 volts in cruise and amps dropped back to a low positive number (barely readable on the original factory gauge but probably about 2 amps).

[PT20J]

A load meter reads from 0 to some positive number and displays the alternator output.

An ammeter reads the current into or out of the battery and has the 0 in the middle since the current can be into the battery (charging) or from the battery (discharging).

Since the first picture shows a negative number (discharge), @dominikos installation is wired as an ammeter.

The meter is actually a voltmeter that reads millivolts with a scale marked in amps. It measures the voltage drop across a shunt. In the case of an ammeter, the shunt is placed in series with the battery connection to the battery bus. A common error when installing digital instruments is to incorrectly set the shunt calibration value. You have to know how many millivolts the shunt drops at rated current.

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[David Lloyd]

Dynon uses a shunt readily available, rated 40mV/40A.  Big G probably uses the same.

[PT20J]

46 minutes ago, David Lloyd said:

Dynon uses a shunt readily available, rated 40mV/40A.  Big G probably uses the same.

Depends. When I had the G3X installed, I just retained the factory EMPRO 70mV/100A shunt. I would think most installers would not replace a functional shunt, but they might not check the calibration.

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