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Runaway overvoltage Need help!

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climberrn

Well Known Member
Sorry for the long post.

Was flying XC talking to Oakland Center today and noticed the voltage going up and down from 12.5-15 volts. I believe my Dynon only reads to 15 volts but not sure. I turned the field wire switch off, no changes. Pulled the 5A circuit breaker for the field and no changes. Was taking a bit of time to process what to do, and after about 30 seconds I see the voltage spike to 15+, hear a "pop" and EVERYTHING goes dark, and I smell electrical smoke for a second. Loose radios, both EFIS's, audio panel, etc. Turned the master off, although nothing had power anyway and used Foreflight on my iPhone to find the nearest airport within reason.

Plane has an "Air Tec" automotive style alternator, less than 300 hours. Full Dynon setup with PS Engineering audio panel, and a couple of GTR-200's. Have PMags and an EarthX battery.

1. The CB's on the PMags popped. Landed with engine power but the engine quit pulling off the runway below a certain RPM. They worked as they should in the air. On the ground with the Pmag CB reset, as soon as I turn the master on, both CB's pop. Talked to Brad at EMag, and will need to send in. He offered to overnight some. Thanks Brad!!

2. Will call B&C tomorrow and get a new alternator that won't fry my panel next time. Any suggestions why I could not shut down the field in flight? They are run through a Cessna style split Batt/Alt switch. Is it a wiring issue, or do the automotive ones keep running once they have power? Don't want to have the discussion about auto vs airplane alternators. I know people that run both. Not for me anymore.

3. Both Dynon screens will not come on. They each have a backup battery, but will not come on at all anymore under their backup battery or ship battery. Pulled my "map data" usb drives but no parameters were written on them prior to shutdown. Pulled screens from the plane and will call Dynon in the morning.

4. Electric trim runs through the AP panel, no longer works when the master is turned on.

Did not try and engage the starter. I "Think" the battery shut down from over voltage protection, but am not sure. The battery indicator light is run through the EFIS.

Fuses on both USB chargers blew as well as some 12V computer fans on the top of the panel. No other circuit breakers or fuses popped. The GTR-200's and the PMA-5000 come on but did not test them, and the flaps work on the ground. Not sure about transponder, ADSB, EMS, AHRS, AP Panel & Servos.

Will get on the phone in the morning to B&C and Dynon and see where I start. Is this something I should call my insurance company about? Not sure what else to check. Wanted to vent and see if there is anything else I should check.

Big thanks to the RV community. Several RV friends offered a hand and 2 RV's flew out to pick my wife and I up. Also got a call from Scott with an -8 based at KMCE. Forgot my iPad on the wing. He has it, and offered a hand to fix the plane.
 
Call your insurance company - they may want you to stop disassembling so an adjuster can look at the plane. A pilot on another list that I subscribe to had a voltage spike from a 12 to 24 volt step up converter that fried his avionics; his insurance company paid his claim.
 
Thanks. I'll call them first thing in the morning. Screens are the only thing removed. Thanks for the heads up.
 
Joel, if the alternator really is set up for external regulation, and you turned off the field with the field CB, there's no way for it to continue producing current.

If it's actually an internally regulated model, it may or may not respond to removing voltage from the ignition (control) terminal. Some older internally regulated alternators will not come on line until voltage is applied to the ignition terminal, but will continue running after ignition terminal voltage is removed.

Either way, overvoltage protection is a very good idea. Are you on the Aeroelectric list?

Charlie
 
Not on aerolectrics list, yet.

Alternator is internal regulated. Going to discuss with insurance, Stein, Dynon and B&C to get this fixed and prevent future problems like this.

My alternator is NOT B&C, it is a reworked automotive version. Has a Mitsubishi mark on the back. But will upgrade now.

After mentally processing it, I believe many people have had an over voltage situation, and the current was absorbed by the battery until the alternator failed. The EarthX battery is designed to disconnect in that situation to prevent bad things from happening to it. When it disconnected, it allowed the alternator to run away voltage even higher. No hard facts yet. Just a hunch.

EarthX and PMags worked as advertised. No fire, and landed with full engine power.
 
All Dynon equipment is designed for 28V planes, so the voltage measurements go 30+V. It's also designed to DO-160 specs, which is what certified equipment uses. This means that as 10-30V operational equipment, it needs to survive 60V. We've left systems hooked to 80V for minutes without damage. They do turn off above about 35V, but come right back on when the voltage comes down.

Thus, the fact that the displays were damaged indicates that voltages got very high.

DO-160 is designed to handle overvoltage from alternators, however, it's designed to do this with a battery still present. An alternator with no regulation and no battery will hit hundreds of volts. The assumption is that the battery is in the system, keeping voltages low(er) until the pilot can disable the alternator. Which makes me wonder if the EarthX battery disconnects itself when the alternator goes unregulated in order to protect the battery? If so, then this requires a very different spec for equipment that would require the equipment to handle the full brunt of the alternator all on their own. Lead Acid batteries had no such disconnect so could be relied on to absorb a lot of abuse. This might be a corner case that the experimental community hasn't considered when using advanced batteries.

Once we get those screens back it will be interesting to see what is in the datalogs and what is damaged and hopefully we can help figure out what happened in more detail. Glad you got the plane down safely!

--Ian @ Dynon
 
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Dang! glad to hear you made it down ok. interesting that the alternator kept charging without field current? hope your Dynon system is ok and not damaged.
 
All Dynon equipment is designed for 28V planes, so the voltage measurements go 30+V. It's also designed to DO-160 specs, which is what certified equipment uses. This means that as 10-30V operational equipment, it needs to survive 60V. We've left systems hooked to 80V for minutes without damage. They do turn off above about 35V, but come right back on when the voltage comes down.

Thus, the fact that the displays were damaged indicates that voltages got very high.

DO-160 is designed to handle overvoltage from alternators, however, it's designed to do this with a battery still present. An alternator with no regulation and no battery will hit hundreds of volts. The assumption is that the battery is in the system, keeping voltages low(er) until the pilot can disable the alternator. Which makes me wonder if the EarthX battery disconnects itself when the alternator goes unregulated in order to protect the battery? If so, then this requires a very different spec for equipment that would require the equipment to handle the full brunt of the alternator all on their own. Lead Acid batteries had no such disconnect so could be relied on to absorb a lot of abuse. This might be a corner case that the experimental community hasn't considered when using advanced batteries.

Once we get those screens back it will be interesting to see what is in the datalogs and what is damaged and hopefully we can help figure out what happened in more detail. Glad you got the plane down safely!

--Ian @ Dynon

Very insightfull here and likely the root cause of the extensive carnage, in my opinion. These Lithium batteries seem to state that they have disconnect circuitry to avoid thermal runaway and it seems likely or possible that they would trip with overvoltage presented from the outside as well. It would seem very difficult to tell which side the overvoltage condition was coming from. I also struggle to see how an alternator can produce in excess of 60 volts with a battery in-line.

I was going to add that many/most internally regulated automotive alternators provide no direct Field circuit access. Unless you pull the alternator apart and cut the field circuit and run it to your switch, there is no way to shut them down. Yes, they have a feed and that must by powered to start them up, but once running they are self-exciting and can't be shut down. There are many exceptions to this, but most work this way. It also can depend upon the failure mode of the internal VR. You should address this on your rebuild to avoid a future incident. This is one of the reasons that I prefer externally regulated alternators. I know that I have positive control of the Field circuit and can shut off the alternators output.

Larry
 
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Have been on the phone with several vendors this morning, and everyone has been very helpful.

Sounds like a perfect storm of things happening. As it stands now, insurance claim process started. Dynon screens, EMS, and AP panel are being sent in. We will not know about the AP servos, transponder or ADSB box until the screens are back in.

Need to check peripherals like USB chargers, Fans which both had fuses blown. The headsets are hard wired through a LEMO plug. Did not think about checking those yesterday.

Mags will be pulled and sent in tomorrow.

B&C alternator is in the mail.

Still deciding what to do with the EarthX battery. It did not cause the problem, but the damage could have been MUCH LESS with a PC680. (or a better designed alternator!)

Did not have a handheld with me. After smelling smoke and everything going dark, honestly, I probably would have done the same thing and landed ASAP instead of fiddling with the radio.

B&C said they have only heard of a couple of failures like this in the last 15 years so I guess I am the lucky one.

Thank you to several in the RV community that have been so helpful.
 
Still deciding what to do with the EarthX battery. It did not cause the problem, but the damage could have been MUCH LESS with a PC680. (or a better designed alternator!)

Wonder what would have happened with a PC680 in this case. How much can it take before it comes apart? And what happens if it does come apart? Worst case could be pretty dramatic - maybe the EarthX saved your bacon! I don't know, just pondering something probably worth knowing.
 
Not enough data to draw a conclusion, but SLA batteries can usually take quite a bit of abuse without turning into torches. If the battery load had remained, it's unlikely that the overvoltage would have ever exceeded the avionics' ability to survive. If the master was pulled within a few minutes of OV detection, it's almost certain that there would have been no collateral damage.

The aeroelectric list is your friend. (hint...hint)

Charlie
 
Did the battery go to safety internal "open" circuit to self protect from overcharge ? and is it still open or normal and showing voltage?
 
Wonder what would have happened with a PC680 in this case. How much can it take before it comes apart? And what happens if it does come apart? Worst case could be pretty dramatic - maybe the EarthX saved your bacon! I don't know, just pondering something probably worth knowing.

This is the beauty of a lead acid battery, they don't come apart or run away. In the case of a runaway alternator, the battery prevents extreme voltages. The battery is like an energy sink/buffer (energy is consumed via the conversion from lead in the plates to lead in the electrolyte). The electrolyte will bubble aggressively and evaporate quickly, but they don't explode, self-destruct or spontaneously combust. (SLA's, like the Odyssey, need to have a vent sized to accommodate this situation, which I presume they do) There is a risk from the combustion of off-gases, but the cowl moves so much air that this should be no issue while in flight. The battery will take a lot of current and therefore keep the system voltage in a reasonable range, at least until the electrolyte evaporates.

Larry
 
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I am way out of my knowledge zone here but, the RV-12 (with ROTAX 912 ULS engine) has a large capacitor installed to deal with the dynamo's over-voltage effects if the main battery is an inadvertently disconnected. I gather that the capacitor gives the uncontrolled voltage someplace to go in lieu of the disconnected main battery. Does any of this apply here???
 
David,
The capacitor on the Rotax is there to deal with the ripples on the output of the regulator when it's functioning. However, it is not effective in limiting an overvoltage case as it has basically zero capacity and will immediately "fill up" and not absorb extra current. This works in the case of a missing battery with a working regulator, where the capacitor only needs to carry power for a few thousandths of a second.

A 22,000uF capacitor is actually tiny in terms of energy storage. In fact, a simple 10AH / 12V battery is the equivalent of about 500,000F, which is 25 million Rotax capacitors. Plus, capacitors don't turn extra energy into heat, but a battery can.

As a bonus, if you hit 50V on a capacitor rated at 25V like the Rotax one, it generally does some interesting and loud things.
 
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I am way out of my knowledge zone here but, the RV-12 (with ROTAX 912 ULS engine) has a large capacitor installed to deal with the dynamo's over-voltage effects if the main battery is an inadvertently disconnected.
Permanent magnet alternators (like the Rotax, or the small B&C dynamos) require a different type of voltage regulator than an conventional alternator, and the large capacitor is part of that system. I'm no EE, but I'm guessing a capacitor large enough to absorb a runway alternator would be larger than the pilot.
 
David,
The capacitor on the Rotax is there to deal with the ripples on the output of the regulator when it's functioning. However, it is not effective in limiting an overvoltage case as it has basically zero capacity and will immediately "fill up" and not absorb extra current. This works in the case of a missing battery with a working regulator, where the capacitor only needs to carry power for a few thousandths of a second.

A 22,000uF capacitor is actually tiny in terms of energy storage. In fact, a simple 10AH / 12V battery is the equivalent of about 500,000F, which is 25 million Rotax capacitors. Plus, capacitors don't turn extra energy into heat, but a battery can.

As a bonus, if you hit 50V on a capacitor rated at 25V like the Rotax one, it generally does some interesting and loud things.

Disk capacitors scare me in an airplane. Had one loose its brain on EXPBUS circuit board, got very hot, caused a lot of smoke in airplane and melted the board - fortunately while taxiing for take off.

The smoke was so intense I shut everything down and bailed out of airplane in parking area. It cooled down with power off.
 
Sorry for the long post.

Was flying XC talking to Oakland Center today and noticed the voltage going up and down from 12.5-15 volts. I believe my Dynon only reads to 15 volts but not sure. I turned the field wire switch off, no changes. Pulled the 5A circuit breaker for the field and no changes. Was taking a bit of time to process what to do, and after about 30 seconds I see the voltage spike to 15+, hear a "pop" and EVERYTHING goes dark, and I smell electrical smoke for a second. Loose radios, both EFIS's, audio panel, etc. Turned the master off, although nothing had power anyway and used Foreflight on my iPhone to find the nearest airport within reason.

Plane has an "Air Tec" automotive style alternator, less than 300 hours. Full Dynon setup with PS Engineering audio panel, and a couple of GTR-200's. Have PMags and an EarthX battery.

1. The CB's on the PMags popped. Landed with engine power but the engine quit pulling off the runway below a certain RPM. They worked as they should in the air. On the ground with the Pmag CB reset, as soon as I turn the master on, both CB's pop. Talked to Brad at EMag, and will need to send in. He offered to overnight some. Thanks Brad!!

2. Will call B&C tomorrow and get a new alternator that won't fry my panel next time. Any suggestions why I could not shut down the field in flight? They are run through a Cessna style split Batt/Alt switch. Is it a wiring issue, or do the automotive ones keep running once they have power? Don't want to have the discussion about auto vs airplane alternators. I know people that run both. Not for me anymore.

3. Both Dynon screens will not come on. They each have a backup battery, but will not come on at all anymore under their backup battery or ship battery. Pulled my "map data" usb drives but no parameters were written on them prior to shutdown. Pulled screens from the plane and will call Dynon in the morning.

4. Electric trim runs through the AP panel, no longer works when the master is turned on.

Did not try and engage the starter. I "Think" the battery shut down from over voltage protection, but am not sure. The battery indicator light is run through the EFIS.

Fuses on both USB chargers blew as well as some 12V computer fans on the top of the panel. No other circuit breakers or fuses popped. The GTR-200's and the PMA-5000 come on but did not test them, and the flaps work on the ground. Not sure about transponder, ADSB, EMS, AHRS, AP Panel & Servos.

Will get on the phone in the morning to B&C and Dynon and see where I start. Is this something I should call my insurance company about? Not sure what else to check. Wanted to vent and see if there is anything else I should check.

Big thanks to the RV community. Several RV friends offered a hand and 2 RV's flew out to pick my wife and I up. Also got a call from Scott with an -8 based at KMCE. Forgot my iPad on the wing. He has it, and offered a hand to fix the plane.

I've gone through three of those alternators in 2 years. I have two fresh spares on the shelf. The symptoms of two failures were exactly how your describe.

I put in a Plane Power internally regulated only because I didn't have time to do the minor rewiring needed to move to a B&C and mount the external regulator. Either way, may sure you have crowbar overvoltage protection.
 
Perhaps EarthX would be interested to take a look at the battery and report findings. From their manual:
In the event of a charging system failure where the voltage increases to above 15.2V, the resistance to charging current increases, and above 16V the charging current is completely blocked. This design offers charge voltage protection greater than 40V. The discharge current (current out of battery) is unaffected in this situation.
Seems that if an overvoltage situation can be controlled, the battery should resume supplying current unless something fries inside.

I wonder whether the crowbar protection circuits, such as B&C's standalone or those built in to their regulators, react fast enough to shut down the alternator before the battery's protection kicks in?
 
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B&C alternator is on order. I know lots of people use an automotive based alternator but I can't go that route anymore. After talking to the insurance adjuster I'm not confident they will pay anything.

PMags will be pulled tomorrow. $125 per mag if they need an overhaul, $425 per mag if the board is fried.

Will pull the alternator tomorrow and have it tested. The insurance company wants that. Will take it to an auto parts store and have it bench tested. They don't want it disassembled at this time. They want an "expert analysis" if things go further.

Dynon suggested pulling the EMS and AP panel. The trim does not work at this time so that could be related to the AP panel. The other boxes will wait until the screens are in to see the extent of the damage.

GTR-200's and audio panel still light up, but will test tomorrow.

Brought a backup radio and headset so I can still ferry her home after the main parts are in.

Scott in Madera has graciously offered some hangar space for working and assistance with the repair. Heading there tomorrow to trouble shoot and pull more parts.

FYI. Anyone running an ignition system totally reliant on electrical power, better be sure you have a backup plan. I thought 2 screens, 2 backup batteries, 2 radios, and a good battery would be enough. Clearly that didn't change anything. Glad the PMags worked when things went south.
 
B&C said the OV protection kicks in after 5MS. Not sure how fast the battery EMS responds but I am considering switching back to a PC-680. I know this is a rare occurrence but it is something for me to loose sleep over.

From what I understand, a lead acid battery can withstand a huge voltage spike for a VERY short period of time. Might have been enough to save my panel. B&C assured me their OV protection would stop the surge, but I may still do more to prevent this from ever happening again.
 
Perhaps EarthX would be interested to take a look at the battery and report findings. From their manual:

Seems that if an overvoltage situation can be controlled, the battery should resume supplying current unless something fries inside.

I wonder whether the crowbar protection circuits, such as B&C's standalone or those built in to their regulators, react fast enough to shut down the alternator before the battery's protection kicks in?

Spoke with Kathy at EarthX this morning also. She was not sure of their cut off voltage and couldn't transfer me to anyone that could. She did direct me to the website that says what you posted. The battery will be bench tested tomorrow also. If the battery OV protection is good to 40v, and the Dynon system has been tested to 80v, then I would suspect the battery has some damage also.

The battery was not providing current a few seconds after the incident. It was working on the ground after shutdown. Not sure when it came back online. Was not a good time to troubleshoot when we were looking for a field, day, VFR with a running engine after smelling electrical smoke. They say hindsight is 20:20. Hopefully I won't get another chance to do this again!

I'll update tomorrow evening with more info.
 
From what I understand, a lead acid battery can withstand a huge voltage spike for a VERY short period of time. Might have been enough to save my panel.

A lead acid battery can withstand serious overvoltage for a LONG time. Like an hour.

The alternator can't put out huge voltage if there's something attached to it drawing a lot of current. That's why it's rated at 60A. It physically can't put out more than that at 12V. Ask for more than 60A and the voltage will be less than 12V.

A fully charged lead acid battery will be at 0 current at 14.4V, but it will be at 100+ amps at 18V. So an alternator with a completely failed regulator can't get anywhere near 18V until the battery boils off the electrolyte, which will take a long time. It won't even be at 60A because the voltage is high, so don't expect it to pop the alternator breaker. But even without an automated overvoltage protector, you should be able to pull the breaker in plenty of time.

The possible issue with the LiFePO4 batteries is that they don't go to high charge current at high voltage, they go to zero charge current. Now that power the alternator is putting out has to go somewhere, and if it can't go into current, it goes into voltage.
 
alternator manufacturer

Hi Joel, did you confirm that the alternator manufacturer is in fact Mitsubishi? I ask because I have an "AIR-TEC, Inc." alternator and it says it's an "N.D. ALTERNATOR" (not sure why they like to shout, but anyway...)

http://www.rv8.ch/wp-content/uploads/2017/03/img_9316-1.jpg

How was your alternator wired to the battery? Did you have a fuse between the alternator and the battery?

My alternator is a 60amp, but I've put on a larger pulley that will probably reduce that to 40amps or so (hopefully keeping it a bit cooler).

http://www.rv8.ch/alternator-pulley-change/

Most experts I've spoken to are not aware of any runaway events with new ND alternators. I have not really confirmed that mine is a ND, just looked at the sticker.

In any event, the alternator can runaway and cause a voltage spike, but the amount of total power it can put out is of course limited.

I'm really happy you shared your story as I had no idea that the voltage could go anywhere near that level. I was also planning on an earthx battery - I might need to rethink that or make darn sure my alternator will cut off automatically if needed.

Good luck with the repairs - I hope it's not as bad as it seems.
 
FYI. Anyone running an ignition system totally reliant on electrical power, better be sure you have a backup plan. I thought 2 screens, 2 backup batteries, 2 radios, and a good battery would be enough. Clearly that didn't change anything. Glad the PMags worked when things went south.

I hadn't thought about it before but this may be part of the reason that Lightspeed specifies that their ignitions be connected directly to the battery terminals.

Glad you weren't flying in IMC when this happened!
 
I hadn't thought about it before but this may be part of the reason that Lightspeed specifies that their ignitions be connected directly to the battery terminals.

...which still would not have helped in this situation, since the battery terminals themselves went cold due the BMS cutting them off.
 
Spoke with Kathy at EarthX this morning also. She was not sure of their cut off voltage and couldn't transfer me to anyone that could. She did direct me to the website that says what you posted.

If this is the whole story, it's very concerning and seems to imply that there are properties to these batteries that even the manufacturers do not know about.

I keep waffling back and forth on whether to swap my PC-680 for a LiFePo4 battery. Leaning back toward the good ol' lead acid now.
 
I spoke to someone at EarthX last year that was very knowledgeable about the inner workings when I had a different issue. Ended up being a bad cell and they swapped it out. For some reason, yesterday I was not able to talk to anyone else.

As for the alternator, it was purchased by the original engine owner when "Air-Tec" used Mitsubishi. I contacted them prior to first start (engine was purchased in crate, fully assembled and factory run), and it was sent in for testing. Was told by air tec that they have since switched to Nippendeso, but mine worked fine.

At the end of a project costs spiral out of control, so I chose to run it until there is an issue then decide to get another or upgrade. Everyone I know has had an alternator failure, and I was ok with that. Figured the Dynon backup batteries would give me plenty of time to land.

Had no idea this could happen.

P.S. My alternator went through a 60amp CB before the battery. It never tripped.
 
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...which still would not have helped in this situation, since the battery terminals themselves went cold due the BMS cutting them off.

Even if the battery went back online, most of my panel is Non-Op. Was going to put in a redundant electric backup for IFR in the future (G5, D10), but this instance really got me thinking. The only electronics that worked were iPhones with ForeFlight. Not my idea if a proper backup, but better than nothing.
 
Years ago when Plane Power and B&C were not as popular I used automotive alternators with internal regulators and when the field was energized the alternator could not be shut down so I used a constant current relay in the B line then activateded it with the field switch I also installed a crowbar over voltage to the relay . The field wire was jupered at the alternator. So when field switch was turned off the alternator was completely out of system . The relay I used was a recreation vehicle dual batter relay available for about $ 15.00 ,hope this may help the people who are using automotive alternators that remain engaged
 
This is a good story to add to the pile dealing with EarthX batteries - if the choice is made to install an EarthX, you absolutely MUST have a positive control method for the alternator field, and ironclad overvoltage protection like a crowbar circuit.
 
Spoke with Kathy at EarthX this morning also. She was not sure of their cut off voltage and couldn't transfer me to anyone that could. She did direct me to the website that says what you posted. The battery will be bench tested tomorrow also. If the battery OV protection is good to 40v, and the Dynon system has been tested to 80v, then I would suspect the battery has some damage also.

The battery was not providing current a few seconds after the incident. It was working on the ground after shutdown. Not sure when it came back online. Was not a good time to troubleshoot when we were looking for a field, day, VFR with a running engine after smelling electrical smoke. They say hindsight is 20:20. Hopefully I won't get another chance to do this again!

I'll update tomorrow evening with more info.

I understand there is still information being gathered but it would appear the regulator failure has been confirmed.

Our receptionist was not able to answer the questions (I was still traveling back from Sun N Fun and you did not speak with me) and did direct him to the website www.earthxbatteries.com to seek information in the manual until a qualified technical person could contact him back if he desired. There is also information in the documentation tab under FACT SHEETS that might also be of interest too.

When a regulator fails, high voltages are possible which is why we strongly recommend having over voltage protection. B & C alternators provide this and so does Plane Power alternators. There is not a certified aircraft out there without this protection too. You can add this safety feature to your plane for a minimal amount of money. (B & C offers a crowbar overvoltage product for $40) If you have this additional layer of protection, it would have automatically taken the alternator off line so that no damage would have happened. Without this level of protection, it is up to the pilot to manually take the alternator off line but the time lag could be enough to cause damage to your electronics.

Has the alternator manufacture been contacted? What did they say about the the failure modes and how high can the voltages go and at what RPM's? I also would ask the question if they have the over voltage protection for the supplied regulator. As Dynon stated earlier, their equipment is protected to 60V. If your alternator can put out more than this during failure, you do not have protection without an over voltage protection circuit.
 
I hadn't thought about it before but this may be part of the reason that Lightspeed specifies that their ignitions be connected directly to the battery terminals.
...which still would not have helped in this situation, since the battery terminals themselves went cold due the BMS cutting them off.

That's a very interesting observation.

The subject airplane didn't have overvoltage protection....but would it make a difference in the case of a battery-fed EI? Here it seems like a race. Given an overvoltage event, will the EarthX shut itself down before the crowbar can take the alternator off line?

Can anyone offer an accurate response time for each system?
 
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That's a very interesting observation.

The subject airplane didn't have overvoltage protection....but would it make a difference in the case of a battery-fed EI? Here it seems like a race. Given an overvoltage event, will the EarthX shut itself down before the crowbar can take the alternator off line?

Can anyone offer an accurate response time for each system?

Great question! B & C Alternators state the overvoltage protection is at 5 milliseconds, the EarthX protection does not engage until 1 second.
 
The EarthX users manual states in part;

"Aircraft over-voltage protection is strongly recommended (i.e. over voltage crowbar circuit)"

The use of an EFIS alone as a battery fault indicator seems counter-intuitive for reasons identified in the ops original thread whereas he lost the EFIS.

The EarthX LED fault indicator seems like a more robust fault indicator partially because it is designed to work with the battery off line whereas the EFIS may not.

To paraphrase, a continuous flashing light indicates greater than 15.2V defined as an over-charge (due to faulty charging system). If in flight, shutoff charging system off immediately.

Shutting off the charging system could be automated by use of aircraft over-voltage protection such as a crowbar circuit commonly found in Planepower alternators and B&C regulators.

What we don't know and need to know is the speed in which the EarthX battery will shutdown when it sees voltages greater than 15.2 volts.

It would also be good to know the speed in which the Planepower alt will go offline when the crowbar circuit detects a fault.

Joel,

I am grateful you got down safe and shared your story. What I've learned has served to make me safer through having a better understanding of how all this stuff works. Best wishes in getting it all back together.

Thank you,
 
Joel, if the alternator really is set up for external regulation, and you turned off the field with the field CB, there's no way for it to continue producing current.

If it's actually an internally regulated model, it may or may not respond to removing voltage from the ignition (control) terminal. Some older internally regulated alternators will not come on line until voltage is applied to the ignition terminal, but will continue running after ignition terminal voltage is removed.

Either way, overvoltage protection is a very good idea. Are you on the Aeroelectric list?

Charlie

I can verify that for the Plane Power alternator, you pull the source voltage breaker and the alternator turns off. This is how I op test my B&C backup alternator.

As has been previously discussed, simplistic power distribution designs that do not allow for major component isolation present good opportunities for fairly straightforward upgrades to provide for isolating failed or questionable components.

Is the conclusion from this discussion that everything else being the same, if this plane had a standard Odyssey battery the result would not have been this extensive damage?

Carl
 
The EarthX users manual states in part;

"Aircraft over-voltage protection is strongly recommended (i.e. over voltage crowbar circuit)"

The use of an EFIS alone as a battery fault indicator seems counter-intuitive for reasons identified in the ops original thread whereas he lost the EFIS.

The EarthX LED fault indicator seems like a more robust fault indicator partially because it is designed to work with the battery off line whereas the EFIS may not.

To paraphrase, a continuous flashing light indicates greater than 15.2V defined as an over-charge (due to faulty charging system). If in flight, shutoff charging system off immediately.

Shutting off the charging system could be automated by use of aircraft over-voltage protection such as a crowbar circuit commonly found in Planepower alternators and B&C regulators.

What we don't know and need to know is the speed in which the EarthX battery will shutdown when it sees voltages greater than 15.2 volts.

It would also be good to know the speed in which the Planepower alt will go offline when the crowbar circuit detects a fault.

Joel,

I am grateful you got down safe and shared your story. What I've learned has served to make me safer through having a better understanding of how all this stuff works. Best wishes in getting it all back together.

Thank you,


There seems to be a bit of some confusion about how the protection works on the battery. It does not "shut down" or "go cold", it still provides battery voltage at the terminals to run essential equipment such as the EFIS or electronic ignition etc. What is does is blocks charging current. Here is the except from the manual:
ETX Hundred Series - BMS
The ETX ?Hundred Series? was specifically designed for the experimental aircraft market (models include the ETX680C, ETX680, ETX900, ETX1200). Only the ETX ?Hundred Series? battery models are recommended for use as the primary aircraft battery (starter battery). In addition to the features found in the ETZ and ETX series motorsports batteries, critical electronic circuits are redundant, the over-charge protection is enhanced and fault indication is included. All components associated with main electronic battery disconnect are redundant. The built-in redundancy ensures that no single point failure results in the battery unintentionally disconnecting. The design aligns with the requirements for a FAA approved lithium battery as per RTCA performance specification DO-311.

In the event of a charging system failure where the voltage increases to above 15.2V, the resistance to charging current increases, and above 16V the charging current is completely blocked. This design offers charge voltage protection greater than 40V. The discharge current (current out of battery) is unaffected in this situation. In addition, EarthX strongly recommends having automatic over-voltage circuit protection (crowbar) for your charging system.

The battery?s micro-controller monitors all failure modes, and reports failures with a built-in LED indicator and discrete output. The discrete output for external fault monitoring is a single wire connection with ?? quick connect terminal. The output is a ?current sinking? type circuit (see diagram below) that can handle 100mA (connects the discrete output to battery ground if a fault is present). This output can be connected to an external 12V LED or general purpose discrete input of an EFIS. The fault output has two states; slow flashing (5 second cycle time) or solid.

The slow flashing fault can indicate an improper state of charge or a problem with the cells internal to the battery. If the battery voltage is outside the normal range of operation, 12.8V to 14.6V, the battery is over-discharged or over-charged, most likely the result of an issue with the electrical/charging system. If the battery voltage is within the normal operating range, with a slow flashing fault, it is indicating an abnormal condition with a cell, such as one cell?s state of charge is very different as compared to the other cells (high cell charge level imbalance). The slow flashing fault may come on briefly during or following periods of high current charging, and is not a concern. But if the fault persist, comes on consistently during changing, or remains (charging or not), the battery will need to be replaced.

The solid fault indicates a BMS hardware failure. For example, if the micro-controller fails the fault indication output is activated (on solid). If the fault persist, comes on and stays on, the battery will need to be replaced.
 
1164284 said:
I "Think" the battery shut down from over voltage protection, but am not sure. The battery indicator light is run through the EFIS.

Kathy thanks for clarifying. I did mistakenly believed the fault circuit on your ETX series batteries actually "shut down" or "go cold".

Thank you,
 
Great question! B & C Alternators state the overvoltage protection is at 5 milliseconds, the EarthX protection does not engage until 1 second.

An interesting thought here. While the crowbar may only take 5ms, nothing comes off line until the breaker trips. Most aviation CB's are of the thermal variety and don't trip at their rated amperage for about 30-60 seconds. The higher the current, the faster they trip. It would be interesting to see how much amperage the crowbar would draw and that would tell us how fast the CB will trip and the Alt source power removed.

This off course is with just the crowbar circuit installed. if you installed their kit, intended for internally regulated Alt's with the a relay installed in-line with the B lead, the alternator output should be dropped in the 5ms specified. I am sure the stated 5ms appies to their packaged alternators, but state this for those assuming they get the same protection with all forms of O/V protection.

If you have one of these batteries and don't have the ability to disconnect an runaway Alt in 1 second, you should assume the same result as the OP with the same failure mode. In a failure of the VR that shorts the Field lead, you should expect a LOT of volts that will ramp up in milliseconds once the battery stops accepting current.
 
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Its not clear to me how the BMS can reject high charging voltage but still maintain output voltage. The circuit is either complete or open. I don't understand how it can be both at once.
 
There seems to be a bit of some confusion about how the protection works on the battery. It does not "shut down" or "go cold", it still provides battery voltage at the terminals to run essential equipment such as the EFIS or electronic ignition etc. What is does is blocks charging current. Here is the except from the manual:

So in the event of a large overvoltage regulator failure, the BMS would block charging current (above 16.0 volts anyway) and as soon as the overvoltage situation was resolved by tripping the alternator offline, the battery is still online and available for discharge with zero delay, is that correct? This of course does not stop the system buss voltage from rising wildly, as apparently happened - but the battery does remain available?
 
Its not clear to me how the BMS can reject high charging voltage but still maintain output voltage. The circuit is either complete or open. I don't understand how it can be both at once.

While there a many ways to do it, think diode. It is rejecting all incoming current once it reaches a threshhold voltage and expiration of the one second timer. It is not limiting the input to a specific voltage. It likely rejects incoming current with a diode type approach that still allows outgoing current.
 
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I think the way it is written is confusing. If the battery voltage is lower than the bus voltage then the battery won't be providing any current.

Its likely they have a mosfet in series and simply open up the mosfet when the overvoltage condition is detected. The overvoltage circuitry also has some maximum voltage that it can withstand so depending on the design that circuitry could be damaged in extreme overvoltage conditions.
 
Is the conclusion from this discussion that everything else being the same, if this plane had a standard Odyssey battery the result would not have been this extensive damage?

Carl

What I derive from this discussion is that over voltage protection is a must in any system.
 
An interesting thought here. While the crowbar may only take 5ms, nothing comes off line until the breaker trips. Most aviation CB's are of the thermal variety and don't trip at their rated amperage for about 30-60 seconds. The higher the current, the faster they trip. It would be interesting to see how much amperage the crowbar would draw and that would tell us how fast the CB will trip and the Alt source power removed.

I've had the crowbar module (externally regulated alternator) now sold by B&C on my RV-6 since it first flew in 1999. When the plane was new, I would occasionally have the alt field breaker trip when the landing lights were turned off after landing. 'Lectric Bob Nuckolls stated this was due to momentary current inrush as the lights were eliminated from bus voltage before the regulator had time to catch up. Regardless of what caused the fault, the field breaker popped "instantly" upon hitting the landing light switch. Every instance I've heard of where the crowbar energized it resulted in an "instant" tripping of the breaker. Bob originally had a crowbar 'test switch' in his schematic to short out the crowbar and confirm it popped the breaker. He later eliminated the switch after deciding it but more stress on the module that was beneficial.

All of the above is from my memory banks from nearly twenty years ago...... :eek:
 
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Its not clear to me how the BMS can reject high charging voltage but still maintain output voltage. The circuit is either complete or open. I don't understand how it can be both at once.

Me too. And the OP quite clearly stated:

The battery was not providing current a few seconds after the incident. It was working on the ground after shutdown. Not sure when it came back online.
 
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