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Over voltage required for EarthX battery

My own regulator appears to control peak voltage with the battery disconnected, but no one seems to know exactly how well. EIS indications suggest output voltage oscillating like an erratic yo-yo. However, it does not trip the crowbar, so it's not getting real high. I've picked up a new toy (a Dataq DI1000), so I'll soon have hard numbers (peak, average, etc) on extended no-battery alternator output voltage. Later I'll look at load dump, the bus voltage peak just as the battery disconnects..



Because when the regulator failed, the resulting high voltage burned through the internal BMS disconnect. Se post 28.

That's a pretty nifty little toy you have there. For anyone that might be looking for an alternative, eLogger V4 from Eagle Tree Systems is an incredibly reliable unit, and almost unbreakable, from the RC & FPV world. With 4 hours of datalogging capability it would suit most tests. Pretty cost effective also.
 
Crowbar?

So I am using an EarthX in my ship. Now I'm a bit concerned about the runaway. I understand what a crowbar circuit is but have no idea where or how to acquire one. Do we build the circuit? Is it a commercially available product?
 
What about using a clamp to prevent over voltage?
That is what we used in data centers. (I barely know the difference, but from what the EE explained the clamp does not require all power cut to turn off. It just caps the voltage, required when you did not want to turn off the computers)

Tim
 
What about using a clamp to prevent over voltage?
That is what we used in data centers. (I barely know the difference, but from what the EE explained the clamp does not require all power cut to turn off. It just caps the voltage, required when you did not want to turn off the computers)

Tim

That is kinda the job of the voltage regulator which controls the field current only generating enough energy to satisfy the load. To clamp a runaway alternator you would need the clamp to dissipate all the excess energy that the alternator is producing. Let?s say you have a 60A alternator and your aircraft is consuming 10A. Than means the clamp would have to dissipate 650W in heat (W = V * A).
 
Perhaps it would be best if Kathy explained the voltage limitation of the MOSFET used for overvoltage disconnect.

Per EarthX's engineering: the over-voltage protection does use MOSFETs. MOSFETs have a NPN junction, so it is like two diodes back to back. You can google how they work, but OHMs law does not apply here. They do however behave similar to diodes in respect to reverse breakdown voltage. That is at a certain "high" voltage current will flow "backwards" through the device. The reverse breakdown voltage is 100 volt.

Now we also have to talk about the time durations. Voltage spikes or surges are typically in the micro-second or milli-second range. The EarthX battery as well as any aircraft equipment is designed to handle these spikes up to and exceeding 100 volts, not sustained. Voltage spikes are not long enough to cause reverse current to flow in the MOSFET. And they are not long enough to damage aircraft electrical equipment.

Unloaded alternators have also been discussed here. An alternators output without a battery and or unloaded, as Dan pointed out, has a high ripple voltage. But the voltage ripple is also in the hundreds of hertz, so only in the milli-second time period. So again, not long enough time to trip over-voltage (crowbar), or damage any electronics. Plus, even without a battery, it still is not unloaded. Any little bit of aircraft electrical load with it's capacitor and inductors help to stabilize the alternator output


As far as Boeing, the 787 uses lithium cobalt chemistry and has over 20 million hours of trouble free operation with a lithium battery
 
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I kinda thought we all had one these days...the ubiquitous EFIS. Mine is set to display an alarm at about 13v on the low end and 15v on the high end.

I know, right? Yet the aircraft that started this whole thing either didn't have one or the pilot did not or could not flick off the alternator.

For someone who doesn't have an EFIS/EMS, the standalone unit is a great option - cheap and easy.
 
Some points of info, in no particular order:

OV annunciation is OK, but with OV protection that removes the offending source, low voltage annunciation effectively serves the same purpose while in flight, by letting you know you've got a charging system failure. With OV protection in place, all you really need to know *while in flight* is that you've got a charging system failure & you need to appropriately plan to get on the ground.

Load dump: As others have pointed out, some new alternators/regulators have load dump protection built in. But many older alternators/regulators do not (I've experienced a load dump failure.) If you have a charging system *without* load dump protection built in, and the battery has the ability to disconnect itself, then it has the ability to cause a load dump failure of the charging system.

Bonus load dump data point: If the battery is fully charged, then a battery disconnect would not cause a load dump because it wouldn't be presenting any load to the charging system.

Clamps: Technically, yes; practically, not so much. OV protection with typical external regulators simply crowbars the ~5A field line to ground; easy to do with light weight, cheap components. To clamp the B lead output, you'd need to either insert a variable resistance in line with the B lead (failure mode issues, a lot of heat when activated, heavier, expensive for the high current device, etc), or shunt the extra current to ground with a variable resistance (again, all of the above).
 
From post #56, this thread:

Per EarthX's engineering: the over-voltage protection does use MOSFETs......The reverse breakdown voltage is 100 volt.

Now we also have to talk about the time durations. Voltage spikes or surges are typically in the micro-second or milli-second range. The EarthX battery as well as any aircraft equipment is designed to handle these spikes up to and exceeding 100 volts, not sustained. Voltage spikes are not long enough to cause reverse current to flow in the MOSFET. And they are not long enough to damage aircraft electrical equipment.

From post #1, this thread:

He did not have over voltage protection on his plane.

During his flight, his regulator failed and his voltages climbed up and remained at +29V and 40+ amps for many minutes. (After approximately 6 minutes, his alternator failed too). A couple of times the voltage spiked above 60V per the data from the EFIS. The over voltage protection for the EarthX batteries is a maximum of 60V, even though the FAA requires protection only up to 19.8V. When the voltages spiked, it was enough to cause a cell rupture as the pilot smelt a funny electrical smell and with continued high voltages and amps, the battery did go into thermal runaway.

Sustained voltage 29+, spike above 60v, BMS failed to protect cells.

Look, I realize some readers will take the position that the BMS should be able to fend off anything an unrestrained alternator might do, and obviously it can't in its current iteration.

Personally I think it's really dumb to not have fast, fully automatic alternator OV protection (with lithium or lead acid), and with it, I don't think a 100v, or a 60v, or even the FAA's 19.8v protection limit is unreasonable for the EarthX's BMS. I just want to know for sure how it works. Think about it. Don't you want TCs, A&Ps, and DARs to be able to speak with authority when they insist on alternator OV protection with your battery?
 
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Based working on IT systems for building control and data centers. I tend to think in big over complex solutions with five and six nines of uptime. e.g. Clamp, capacitor systems for automatic voltage regulation....
Consider the size of the electrical system in the plane; I keep coming back to the idea of using a dual battery solution. A small lead acid battery to act as the buffer for the primary electrical load variation and in case of alternator failure (over voltage or over current); then a EarthX type battery to provide ship power and starting juice.
For such a solution, how big of a lead acid battery would be required? And at that point, is a more sophisticated Li battery still worth it?

Tim
 
KitPlanes article

Folks,
If you haven?t done so, take a look at this month?s KitPlanes Magazine article on EarthX and lithium. Jared Yates wrote a great and informative piece on the company, with plenty of useful info on the EarthX technology, lithium battery chemistries, and some specifics on this very subject (over-voltage protection). Kathy is brilliant as usual as the voice of EarthX.

Between the article and this thread, I see two chief takeaways as they relate to this whole conversation:
1. ?Lithium battery? is a gross simplification of an array of chemistries used for batteries.
2. Overvoltage protection is non-negotiable, but it comes in several forms. Crowbars, B&C, Vertical Power VP-X...have it.

Ironflight, please pass on my kudos to Jared for an excellent article.
 
How fast is your chosen OV protection?

I expect that an objective study and presentation of the speed of the various over voltage devices will soon be in order. A friend had an OV event in his RV 10 that nuked both his AFS displays internal OV protection along with other avionics. The VP-X was not fast enough to prevent that. Had it been in solid IMC he had zero flight instruments remaining.

The RV 10 had SLA batteries, with an internally regulated auto alternator.

Is your OV protection fast enough?
 
While OV protection sure seems like a great idea, has there been any investigation why airplanes seems to suffer more OV events than cars? What do cars do differently than we do, and should we adopt those practices?

The only alternator OV event I've ever had was 25 years ago on an ancient AC Delco external regulator when the points stuck.
 
More points of info:

With our systems, there are really no 'over current' events, in the sense of a power source problem. You can have a component failure in a load (or a wire), that causes a partial or total short to ground, but this is not a power supply issue. When you see higher currents during an alternator/regulator failure, it's due simply to Ohm's law operating on a fixed load resistance and a higher supply voltage.

On OV protection speed: With properly designed OV protection circuits, that is not an issue. How fast is a light switch? How fast is a transistor or other semiconductor? A relay (contactor)? No sensible designer would design a/c OV protection that waited minutes to activate. If it's working properly, it will do its job within a fraction of a second after voltage exceeds the setpoint. Most will have a built-in delay of a fraction of a second (delay can vary with the level of excess voltage) to avoid nuisance trips, but many seconds to minutes of delay is not a baked-in feature. On the RV-10/VPX incident: Either the VPX OV protection circuit was faulty, or the wrong combination of components was used. The make/model of IR automotive alternator wasn't specified. Many IR alternators cannot be shut down using their 'I' terminal, in contrast to the Plane Power alt. If the alternator in use was one of those models, then the VPX wouldn't be able to control it, unless the builder wired the B lead circuit to mimic the B lead wiring diagram for the B&C SD-8 (contactor that interrupts the B-lead). This is the install manual I checked before writing this:
http://verticalpower.com/media/attachments/2017/07/21/ma191_vp-x-installation-and-operating-manual_c.pdf

Charlie
 
While OV protection sure seems like a great idea, has there been any investigation why airplanes seems to suffer more OV events than cars? What do cars do differently than we do, and should we adopt those practices?

The only alternator OV event I've ever had was 25 years ago on an ancient AC Delco external regulator when the points stuck.

I have no data for you, but I'd suspect that some reasons are: Cars have much more carefully engineered *systems* than a/c, to drive down callback costs to the mfgr. Also, a lot of us (me included) are buying auto alternator models that originally ran on cars 3 or even 4 decades ago. They're still the same alternator, with the same tech inside, just like a/c magnetos haven't changed. The early stuff likely has failure modes that have been beaten out of (or compensated for) in more modern alternators. 'Load dump' immunity would be a pertinent example.
 
Does the claimed 200ms period for cutting off an OV condition seem long? The SCR-based "crowbar" mechanisms are on the order of a few tens of milliseconds.

The designer posts fairly often on the Aeroelectric List. I'd bet that if you ask him, he'll tell you that the 200 ms delay (time constant) is baked in on purpose. Someone on that list recently posted an engine monitor time/voltage graph with millisecond resolution, showing how 'unstable' the bus voltage looked, thinking he had a problem. Reality is, the bus voltage in any alternator powered system is moving around a lot, down in the millisecond range. When you get into that kind of detail, you're watching the sausage being made. Instant response of the OV module would result in nuisance trips.
 
The designer posts fairly often on the Aeroelectric List. I'd bet that if you ask him, he'll tell you that the 200 ms delay (time constant) is baked in on purpose. Someone on that list recently posted an engine monitor time/voltage graph with millisecond resolution, showing how 'unstable' the bus voltage looked, thinking he had a problem. Reality is, the bus voltage in any alternator powered system is moving around a lot, down in the millisecond range. When you get into that kind of detail, you're watching the sausage being made. Instant response of the OV module would result in nuisance trips.

I agree the bus voltage isn't steady, but I'd challenge the notion that a 20 millisecond response time (for example) would result in nusiance trips. After all, that's about what many SCR-based approaches have and it seems like it'd be something we hear about more frequently if they were in fact an issue.
 
Folks,
If you haven?t done so, take a look at this month?s KitPlanes Magazine article on EarthX and lithium. Jared Yates wrote a great and informative piece on the company, with plenty of useful info on the EarthX technology, lithium battery chemistries, and some specifics on this very subject (over-voltage protection). Kathy is brilliant as usual as the voice of EarthX.

Between the article and this thread, I see two chief takeaways as they relate to this whole conversation:
1. ?Lithium battery? is a gross simplification of an array of chemistries used for batteries.
2. Overvoltage protection is non-negotiable, but it comes in several forms. Crowbars, B&C, Vertical Power VP-X...have it.

Ironflight, please pass on my kudos to Jared for an excellent article.
Sid, when you say "this month's" Kitplanes, what month are you refering to? I have gone through the November issue and do not see what you are referring to. If you are talking about a December issue, well, you must have better mail delivery than I do.
 
Sid, when you say "this month's" Kitplanes, what month are you refering to? I have gone through the November issue and do not see what you are referring to. If you are talking about a December issue, well, you must have better mail delivery than I do.

Steve,
Excellent point, sorry. It?s the December issue, in the mail now (mine just arrived).
 
Here we go

Perhaps it would be best if Kathy explained the voltage limitation of the MOSFET used for overvoltage disconnect.


Depends upon how we define "part of the problem". A battery is a required system component. Here it's one of several possible victims, not the perpetrator.


Different battery chemistry.


Always.


Just something to measure and understand. Why? Because all our airplanes are capable of that load dump...yours, mine, everybody.

While on that subject...the load dump apparently does not spike my system voltage very much, i.e. the regulator is able to hold voltage to a reasonable level even without the battery. How do I know? The OV crowbar doesn't trip. A few phone calls; the 12V Plane Power regulator shorts the field at around 16.5v, and a B&C shorts the field at 16v.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1. Lets hear the explanation. I do not have complete faith in any of their explanations, with their private message giving me reservations.
2. So you are saying that the battery is the victim and in no way part of the problem. "Show me the data". I believe it may be part of the problem. Really, no one here is saying a battery is not required
3. I never said it was the same chemistry. The Earth X does have some similar shortcomings. Boeing is a good example in that their large amount of engineering experience did not anticipate all the problems that could occur. So, there are definitely similarities in the problems seen with Earth X batteries
4. We finally agree. I feel better now.
5. Would your load dumped system cook the battery. Maybe not. Would any other alternator system perform the same as yours? Some obviously not. One would have to similarly test their own system and see what happens. Good data though. It takes some financial guts to run stuff to possible expensive failure. Please run a B&C alternator and crowbar with a ford regulator and let us know the results. Ill supply the regulator if necessary. (Attempt at humor).

I do the like the "probable cause" from the Bill Palmer report. A well written report, but a lot of "speculation" going on. "CAUSE UNKNOWN", I agree.

George
 
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Here we go

I do the like the "probable cause" from the Bill Palmer report. A well written report, but a lot of "speculation" going on. "CAUSE UNKNOWN", I agree.

George

The failed regulator definitely was the root cause, the battery BMS definitely failed to protect the battery from excessive voltage. This battery chemistry will exhibit thermal runaway. That is no speculation. If you want to keep flying and believe that 20 million hours from Boeing will help, then go ahead a feel good about it, but that is no protection from the failure mode. Obfuscation like this post prevented a solid technical discussion from allowing Bill Palmer to fully know what he was getting into. Only a OVPM, and an externally vented battery box would mitigate the failure modes exhibited here. These two items have been stated before, so this is not just hindsight.
 
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The failed regulator definitely was the root cause, the battery BMS definitely failed to protect the battery from excessive voltage. This battery chemistry will exhibit thermal runaway. That is no speculation. If you want to keep flying and believe that 20 million hours from Boeing will help, then go ahead a feel good about it, but that is no protection from the failure mode. Obfuscation like this post prevented a solid technical discussion from allowing Bill Palmer to fully know what he was getting into. Only a OVPM, and an externally vented battery box would mitigate the failure modes exhibited here. These two items have been stated before, so this is not just hindsight.
Could everyone please make a point to understand the chemical differences between the various batteries labeled as "Lithium" out there in the world. To be very clear, the "Lithium" batteries Boeing had problems with a few years ago in no way have the same chemistries as the LiFePo4 batteries we are discussing here.

This discussion should not be one steeped in emotion (yes, fear of death is an emotion). So, in that light Bill, I am not sure what obfuscation you are referring. All discussions on this thread are very valuable pieces of information.

Ultimately, however, as you have eluded to here, how one deals with the information when it comes time to install, or not install, ANY component into their personal aircraft is still a decision that will be based on individual personal bias. To go even further, that personal bias will either be based on emotion or on information. I personally choose to base my personal bias on as much information as I can find. So, I personally have read, and shall continue to read, every post on this thread with great interest, no matter what position the poster holds.

Live Long and Prosper!
 
Built and tested, never flown

This device looks interesting, anyone using this for OVP?

http://www.periheliondesign.com/lovm.htm

I built a replacement panel for my 6A that employed the Perihelion module to protect the avionics from OV via relay feed to the Av Bus but still left the battery and landing light loads connected to the master (to be dumped manually by switch activation if the OV warning came on) and the whole set-up was bench-tested with a variable voltage supply, performing exactly as intended. My intention was to use the battery and other relatively robust resistive loads to buffer the rate of rise of an OV event while allowing instantaneous isolation of the avionics. I subsequently lost the panel and all written/digital documentation in a house fire before the panel was ever installed and flown.

This gizmo is just an OV crowbar with an electronic breaker, test switch and warning light. Nothing beyond essential function offered by other modules with the same purpose. Regardless of the hardware used to execute the circuit, OVP remains essential to the task of using lithium batteries in aircraft. Nuisance trip vulnerability is an issue worth looking at, as they could potentially really complicate your day in IMC.

Personally, I'm waiting for Bob Nuckolls to finish testing and finally release the long-awaited AeroElectric OV module for IR automotive alternators that now exists only as a mysterious black box in his Z-diagrams. In the mean time, I am using his since-redacted contactor in the B-lead that pops along with the Field breaker when the crowbar does its thing.
 
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The failed regulator definitely was the root cause, the battery BMS definitely failed to protect the battery from excessive voltage.

Dear Bill,

All products have limitations and the EarthX BMS is no exception to this. We can protect up to 60V and no more. We are trying to be very clear on this subject by saying this is above the limitations of the BMS design.

The FAA requires voltage protection of a lithium battery (for a certified battery) to be 19.8V. We protect up to 60V based on knowledge gained by working with many aircraft manufacturers and engine companies.
We also test the batteries to the standards set forth in RTCA DO-347 and RTCA DO-160 for a certified battery installation for an aircraft.

When you have a regulator failure, you can experience voltages above 60V depending on your alternator/regulator. You can also experience high amperage. As an illustration of what happens in a situation such as this, whatever battery is on the receiving end of this failure, lead acid or lithium, it is the recipient of a lot of energy. The average microwave is 600-1200 watts, if you are experiencing 29.1V and 44 amps from your charging system, that is (V X Amps = watts) 1280.4 watts of energy. With a lead acid battery, this amount of energy can cause a thermal runaway the same as a lithium battery. What happens in thermal runaway is different per battery but neither is something anyone wants to experience.

We started this thread as we have customers with all types of backgrounds, experiences, abilities, knowledge and quality of aircrafts. In theory, your regulator is designed to keep the voltages in a safe range. If it fails, and if you have over voltage protection, that would be engaged and protect from unsafe voltage ranges in milliseconds. If that fails, you then resort to manual shut off of the alternator/generator. This would be considered triple redundancy of protection. If that doesn't happen, then you can have thermal runaway with ANY battery. Nobody wants this to happen. If you do not have over voltage protection, then you have reduced your redundancy and safety level and using this incident report as an example, having the pilot manually turn off the alternator/generator does have room for error even though you know what to do, to err is human.
 
Will Vertical Power Primary Power System Protect the Battery?

I am on the list for the new Vertical Power Primary Power System. I assume that this solid state system will protect the battery and electrical system from such over voltage excursions. Is that the case?
 
Do I understand correctly that the overvoltage protection of EarthX batteries works only until the voltage becomes really overly excessive? And that a crowbar OVP is required in any case, just like with any other battery?
If that's the case, what does it make an EarthX "aviation" battery any more "airworthy" than any other lithium battery from one of the major brands (for example, Shorai) with comparable Ah and CCA ratings? In many cases, you could get a "motorcycle/powersport" lithium battery with similar ratings for significantly less $ and it would even weight less than the "aviation" battery.
 
Chad, what say you?

I don?t doubt Dan, but I would like to have a little more explanation. Is the solid state architecture not able to handle a runaway alternator.
Thanks,
 
To save Dan a little time, look at page 9 of the PPS installation manual. There's no control over the field lead provided by the PPS.
 
The PPS does not have ability to shut off the alternator, it is simply a solid state contactor/solenoid system. The VP-X provides over-voltage protection, the PPS does not.
 
The PPS does not have ability to shut off the alternator, it is simply a solid state contactor/solenoid system. The VP-X provides over-voltage protection, the PPS does not.

Chad, can you supply some details about the VPX OV protection? I suspect a lot of VPX purchasers are early adopters, and thus more likely to also install an EarthX or similar...even when they don't understand any of it.

From the VPX installation manual:

Over-voltage protection is provided by removing power from the Field wire when the bus voltage exceeds a pre-set limit for a pre-set period of time.

The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?

In reviewing the manual, I note that users are expected to configure the trip point for 12v or 24v systems. If a user fails to configure a 12v system properly (sets for a 24v system), the OV protection will be useless with some LFP batteries and they will smoke. An EarthX BMS should disconnect at 16v, so a misconfiguration should not be a problem. Regardless, perhaps this point should be made much more obvious to purchasers.

I expect that an objective study and presentation of the speed of the various over voltage devices will soon be in order. A friend had an OV event in his RV 10 that nuked both his AFS displays internal OV protection along with other avionics. The VP-X was not fast enough to prevent that. Had it been in solid IMC he had zero flight instruments remaining.
The RV 10 had SLA batteries, with an internally regulated auto alternator.
Is your OV protection fast enough?

Pretty good example of a user not understanding the system. The user apparently connected the VPX to an auto alternator that, once running, could not be shut down by disconnecting its field wire. If that's not the case (the alternator design would in fact halt output with a field disconnect), then the VPX had an issue.

Here's a question...we know Plane Power and B&C (with B&C regulator) have OV protection, and the VPX can open the field on either, which effectively doubles the OV protection. Are there any other alternators in the marketplace which can be shut down by opening the field lead?
 
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The VP-X OV protection on a 12v system is set at 15.9, and 31.9 on a 24v system. I don't know the timing, but I will find out...milliseconds though.

I agree with you on the info in the manual needing to be more obvious with better technology batteries available now, I will take that as an action item for immediate revision.

I'll get the timing info as soon as I can. I am out of the office today, but if I'll shoot an email to engineering before I leave the house today.
 
Dan,

In the interest of using precise terms, I don't think we should call that terminal on internally regulated alternators a 'field' terminal. In the IR alternators I'm familiar with, it doesn't connect to the field; that's why it won't control the alternator after startup. If memory serves, it's actually a control input that tells the regulator to turn on. And in alternators with that particular style regulator, the regulator, once told to turn on, will 'latch' on & the latch won't drop until the alternator stops spinning (making power).

Calling it a 'field terminal' can give the (wrong) impression that an alternator can continue to produce power without the field winding connected.
 
Dan,

In the interest of using precise terms, I don't think we should call that terminal on internally regulated alternators a 'field' terminal. In the IR alternators I'm familiar with, it doesn't connect to the field; that's why it won't control the alternator after startup. If memory serves, it's actually a control input that tells the regulator to turn on. And in alternators with that particular style regulator, the regulator, once told to turn on, will 'latch' on & the latch won't drop until the alternator stops spinning (making power).

Calling it a 'field terminal' can give the (wrong) impression that an alternator can continue to produce power without the field winding connected.

In the IR alternators I use, pulling power off the field terminal certainly stops the alternator from charging.
 
From my experience

Chad, can you supply some details about the VPX OV protection? I suspect a lot of VPX purchasers are early adopters, and thus more likely to also install an EarthX or similar...even when they don't understand any of it.

From the VPX installation manual:

Over-voltage protection is provided by removing power from the Field wire when the bus voltage exceeds a pre-set limit for a pre-set period of time.

The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?

In reviewing the manual, I note that users are expected to configure the trip point for 12v or 24v systems. If a user fails to configure a 12v system properly (sets for a 24v system), the OV protection will be useless with some LFP batteries and they will smoke. An EarthX BMS should disconnect at 16v, so a misconfiguration should not be a problem. Regardless, perhaps this point should be made much more obvious to purchasers.



Pretty good example of a user not understanding the system. The user apparently connected the VPX to an auto alternator that, once running, could not be shut down by disconnecting its field wire. If that's not the case (the alternator design would in fact halt output with a field disconnect), then the VPX had an issue.

Here's a question...we know Plane Power and B&C (with B&C regulator) have OV protection, and the VPX can open the field on either, which effectively doubles the OV protection. Are there any other alternators in the marketplace which can be shut down by opening the field lead?

The Denso 14824 is controllable thusly. I was able to turn it on and off several times under load when the regulator or associated wiring failed in flight and produced a 36v OV event. This was before I rewired my ship to have a crowbar and a B-lead contactor controlled by same. The "field" terminal did in fact control the alternator's on-off state.
 
alternator control

I've tested internally regulated alternators and they do turn off and on with the "control" wire under normal circumstances. The question that I've read posed by those much more expert on this than I am is "will the alternator turn off if there is a failure of the internal regulator?"

There is a risk that they will not turn off, so Bob Nuckolls has proposed this solution, which seems quite solid.

ProposedAlternatorB-LeadDisconnectOVdesign-1024x344.png


The tricky part is to find the TVS device - I bought one from Eric, but he does not sell them any more for some reason. (http://www.periheliondesign.com/)
 
What about the "interim" figure Z-24 solution from the Bob Nuckolls book?
I understand that the only issue with that approach is that some internally regulated alternators may get fried if they are "turned off" by disconnecting the B lead. Which I wouldn't mind as much as I'd expect it to happen in a situation where the alternator would need to be replaced anyway. Plus, we would be talking about a less than a $100 automotive alternator and not the $$$$$ "aviation" model.
What am I missing?
 
Mickey, are you sure that schematic was for a full blown OV event, or for surge mitigation? Doesn't look very 'Bob-like', since the TVS would be required to take the full current of the OV event until the alt dies completely, or the flight ends.

I share the concern about expecting an internal regulator that has failed, causing an OV event, to then provide the protection from itself.

Kalibr, IIRC, the reason Bob pulled the drawing was that builders were combining it with an alternator control switch, and flipping the switch off in flight, killing the alternator due to 'load dump'. If you use the circuit, and treat the system like the ones in cars (alt always on), it works fine, with positive control of OV events. And you can't kill an alt that's already dead. :)

Charlie
 
In the IR alternators I use, pulling power off the field terminal certainly stops the alternator from charging.

I don't doubt that. But, and it's a big but, there are a lot of older IR alternator designs still out there that don't work that way. If we're depending on the control terminal to shut it down, we need to test to be sure it does what we think.

There are probably rebuilt alts on the market that have the same model number, but different internal regulators. Some will work like yours, but there's a good chance that others will be the old style 'on only' control terminal. And as I mentioned in another post, I'm not comfortable with expecting the regulator that just failed to properly control voltage to then protect the system from that overvoltage. Anyone who's done electronics repair work at the component level knows that sometimes a single component can fail, and other times that component can take multiple others with it.

Charlie
 
Charlie, thank you. It confirms my understanding. If I have a crowbar OVP I see no reason for the need to turn off an alternator manually. As such, I think an internally regulated automotive alternator when installed with a crowbar OVP trigger hooked to a contactor in a B lead circuit provides a safe, reliable and very economical solution compared to "aviation" externally regulated alternators. As icing on the cake, this crowbar B lead contactor hookup makes it sensibly safe (as far as overvoltage protection is concerned) to use common lithium motorcicle/powersport batteries, again saving $$ in the process.
I am in the process of designing an electrical system for my build. I am trying to keep it light, simple and economical without compromising the safety. At this point I am not convinced I should be spending extra $$ for "aviation grade" alternators and batteries, which are generally not only much more expensive, but also heavier, more complicated to install (the need for an external regulator), but provide zero additional safety or utility compared to "automotive" replacements.
But I am very open minded and would be very receptive to being convinced otherwise.
 
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BTW, the Z-24 figure appears in the current edition of the Bob Nuckolls book. It is marked as "interim", but it is not "pulled" or otherwise recalled. Maybe it was pulled at some point, but it is back in the book now.
 
Yep; it was gone for years, and the most recent revision had it reinserted.

I'm using the IR alt with that circuit on my -4, and my alt engine powered -7 will use a pair (dual IR alts with dual contactor circuits).
 
I don't doubt that. But, and it's a big but, there are a lot of older IR alternator designs still out there that don't work that way. If we're depending on the control terminal to shut it down, we need to test to be sure it does what we think.

There are probably rebuilt alts on the market that have the same model number, but different internal regulators. Some will work like yours, but there's a good chance that others will be the old style 'on only' control terminal. And as I mentioned in another post, I'm not comfortable with expecting the regulator that just failed to properly control voltage to then protect the system from that overvoltage. Anyone who's done electronics repair work at the component level knows that sometimes a single component can fail, and other times that component can take multiple others with it.

Charlie

Every Denso alternator I've seen (and that's a lot) with a separate field terminal works this way. I don't use ones without a field terminal on anything, especially aircraft. You're simply complicating your life if something goes wrong.
 
Do I understand correctly that the overvoltage protection of EarthX batteries works only until the voltage becomes really overly excessive? And that a crowbar OVP is required in any case, just like with any other battery?
If that's the case, what does it make an EarthX "aviation" battery any more "airworthy" than any other lithium battery from one of the major brands (for example, Shorai) with comparable Ah and CCA ratings? In many cases, you could get a "motorcycle/powersport" lithium battery with similar ratings for significantly less $ and it would even weight less than the "aviation" battery.

Thank you for the questions. No, you are not correct about the overvoltage protection on the EarthX. The over voltage protection begins at 16V and can continue to protect up to a voltage of >60V. In the EarthX manual this protection is explained in detail.

The crowbar protection is required for alternator/generators that are greater than 20 amps max (non pad mount alternators). This means that if you have a Rotax 912, 914, 915 or 582 engines, you do not need to install an additional crowbar protection as they are 18Ah max output. But if you have a Lycoming IO-360, 60 amp alternator, you do need to make sure that you have over voltage protection. This over voltage protection will also protect all the expensive electrical equipment in your plane too!

You ask, what makes the EarthX aviation battery more ?airworthy? than the common motorcycle line brands on the market, which is a great question. The EarthX aircraft batteries are tested to RTCA DO-347 and RTCA DO-160 FAA standards for lithium batteries used in aircrafts (these are the requirements for a certified battery). There is only one other lithium brand out there that test to this standard and that is True Blue. The ETX680C, ETX680, ETX900 and ETX1200 currently in production and soon the ETX900-VNT have a completely different battery management system than the motorcycle batteries EarthX builds with built in redundancy. This is explained in detail in the manual. They also have LED fault light monitoring which is a means of communications to the pilot to the state of health and state of charge of the battery. What is most important about this is the detection of a defective cell. You do not want to use a defective lithium battery. Note: this is what happened with Boeing, they had a manufacturing defect in some of the cells. If you have no issues with your charging system, but you use a defective lithium battery, you can cause a cell rupture. The difference in price from our motorcycle line to our aircraft one with the same performance spec?s is $30 more for these additional design/safety features. We did not want price to be the reason for someone to choose a motorcycle battery over the aircraft version which does costs more to build.

And for your last question, why not use a motorcycle/powersport brand like Shorai because it is cheaper? As you mentioned Shorai, we will focus on them but the same reason will hold true for many of the lithium batteries on the market too. Please read their manuals for specifics on each brand.
First, Shorai itself specifically states on their website to not use their batteries in aircraft and there is no liability or warranty coverage if you do. Second, the EarthX aircraft batteries are designed for aircraft charging systems and are tested to very high quality safety standards set forth by the FAA (RTCA DO-347, RTCA DO-160). Shorai does not do this. Third, Shorai does not offer batteries with enough capacity for aircraft. Their largest sized battery would be a significant decrease in capacity from what aircraft currently use which is a very important consideration in that if your alternator/generator has failed during flight and you are on battery power only, you don?t just pull over in a plane. Fourth, Shorai has no manual listed that has sizing, performance or design limitation for their batteries. It is not enough to match a lead acid or another lithium battery based solely on cranking amps as you also have to consider charging; you must know the maximum charge current the battery is designed to accept. We have a detailed explanation of this on the website. Fifth, Shorai has no protection built in, they have cells in a plastic case. There is no over discharge protection, no over charge protection, no heat protection, no short circuit protection and no cell balancing technology. EarthX has all of this. And lastly, Shorai has no means to alert you to a cell defect such as the LED fault light indicator that the EarthX does. The importance of this was listed previously in this post.

These are the reasons why aircraft manufacturers do not use the ?motorcycle/powersport? lithium batteries you mentioned or even some of the lithium batteries that are being marketed to the aircraft market. This is also the reasons why the experimental engine companies do not use them. They are not the same and they are cheaper for a reason.
 
That 20 amp number keeps showing up in your posts, but there is no explanation of the engineering or physics behind it.

You just explicitly stated that no overvoltage protection is needed if the alternator is 20 amps or less. You also state that your battery can't protect itself if voltage gets above ~60 volts. Consider this very real scenario:

VFR a/c with minimal electrical loads & 18A alternator (to keep it lower than your spec'd current limit). The regulator fails, and voltage starts climbing. At some point, your battery will be fully charged. There are minimal or no other loads on the alternator. How high will the voltage go? (Hint: pretty good odds, higher than 60 volts.) What happens to the battery?
 
That 20 amp number keeps showing up in your posts, but there is no explanation of the engineering or physics behind it.

You just explicitly stated that no overvoltage protection is needed if the alternator is 20 amps or less. You also state that your battery can't protect itself if voltage gets above ~60 volts. Consider this very real scenario:

VFR a/c with minimal electrical loads & 18A alternator (to keep it lower than your spec'd current limit). The regulator fails, and voltage starts climbing. At some point, your battery will be fully charged. There are minimal or no other loads on the alternator. How high will the voltage go? (Hint: pretty good odds, higher than 60 volts.) What happens to the battery?

Please see post#27 which did address these questions.
 
The voltage trip limit for a 12v system is intended to be 16v like other OV systems (see note below). What is the pre-set time period before disconnection of the field lead?

Wanted to be sure an answer this as soon as I could, 30ms at or above 15.9v or 31.9v before the VP-X shuts off the alt field.
 
Please see post#27 which did address these questions.
I assume that you're referring to this:
So what's different about lithium iron chemistry that makes it able to handle a 20 amp alternator in an overvoltage situation, but not handle a 30 amp alternator in the same situation, meaning the same level of over-*voltage*? Our manual may be causing the confusion when we say over-voltage protection is not required on “<20 Amp pad mount standby alternators”. The confusion is that it has nothing to do with it being a < 20 amp alternator. The real reason is the “pad mount standby alternator”, for a pad mount alternator RPM is much lower and as such the unregulated voltage (in the event of a regulator failure) will be much lower. Low enough that Earth’x BMS can block any charge current at those voltages.

You do realize that PM alternators are being installed on the other end of experimental engines, too, driven by belts at their original design rpm? This is most likely to be done by those obsessing over weight; the same people that will be drawn to lithium chemistry batteries.

For the wound-field models that B&C & others sell for the vacuum pad: Are you saying that your engineering dept has spun one at vacuum pad rpm with the output feeding the field, minimal-to-no load, and the voltage never rises above your 60V threshold?

Oh, and it didn't answer the question....

I ask the above question because if the BMS is *blocking* the voltage, it's removing the load, which will allow voltage to rise (probably a lot). On the other hand, if it's *shunting* the current to ground, it's *supplying* a load to hold the voltage down. So, which?

Please understand that I'm asking these questions because I can't get some of the earlier answers to line up with a couple of careers worth of experience herding electrons. I want the new tech to work, but we need to understand all the differences from the old tech to have confidence in it.
 
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