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EarthX and B&C Charging System

S

stewartb

MEMBER
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A comment in another thread about EarthX not recommending installing a battery inside the cabin had me do some investigation.
 
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So, is the overvolt protected battery now approved for use in certificates aircraft?

Or are they still working on certification?

MTV
 
Last I heard from Cathy they were still working on it. Right after Oshkosh, she said certification was imminent. About 3 months ago, I emailed and asked if she had an update.. One word response was “no”......
 
Reading Cathy's response to Stewarb's email; Wow! that's some serious faa lawyerese! In the event your reg fails . . . then your over voltage protection fails . . . and then the battery receives over 100 volts . . . and you fail to manually take the alternator offline . . . this CAN produce enough energy to induce a thermal runaway.

Now, I'm a big proponent of redundant systems, especially with regards to personnel and equipment safety, but how many layers do you need?! The typical charging system on a small aircraft already has redundant safety measures built into it. First off, an ammeter or voltmeter is required so that the system can be visually monitored. The generators and alternators both have breakers that open the output and/or field power circuits if they sense high current flow. And, finally, the regulator power circuit is run through one pole of the typical two pole master switch so that, when the master is shut off while the engine is running, the charging system cannot self excite. Bonus points if you have over/under voltage lights either in your volt/ammeter or connected to your regulator. AND, some manufacturers like Cessna use a stand alone over voltage module inline with the regulator power circuit. Then other manufacturers come along and build voltage protection into the reg itself.

NO BATTERY will with stand the circumstances described in Cathy's response. At some point the operator has to take control and isolate the problem, it can't just be 'ruled' away. Turn off the charging system when you see and over voltage or excessively high current flow. Or maybe when the light comes on to alert you. Don't keep operating with the above conditions present. Don't override circuit protection systems. At what point do you stop blaming the equipment design and just say 'I should turn it off'?

I'm still a fan of EarthX and I'm still installing them. I would like to hear about the Birchwood battery incident, however. Stewartb, could you share the details of this? If you want, PM or call me.

Web
 
not sure of the why, just have a picture of the battery pieces they ripped out with channel locks... with the smoke in cockpit in the background....

AFTER this happened owner installed a B&C & reg, it was a new to this owner plane/project.... no idea what was installed/brand before...
 
Web, is it possible for a failure in a system to put out 100 volts? Seems like a big number to me.

and then the EarthX BMS is the recipient of over 100V
 
Is it time to mount batteries in an external pod maybe under the gear cabane?
 
It is time to start carrying around large amounts of a chemical that cannot be extinguished once ignited unless you are prepared to armor it like Boeing.
 
There have been 2 or 3 incidents with Earth X batteries and through all my research there was no over voltage protection on the charging system. From what I have studied I am not concerned with thermal runaway with an OV circuit in the charging system and the safe guards EarthX has integrated into their batteries.
 
wireweinie said:
Reading Cathy's response to Stewarb's email; Wow! that's some serious faa lawyerese! In the event your reg fails . . . then your over voltage protection fails . . . and then the battery receives over 100 volts . . . and you fail to manually take the alternator offline . . . this CAN produce enough energy to induce a thermal runaway.

Now, I'm a big proponent of redundant systems, especially with regards to personnel and equipment safety, but how many layers do you need?! The typical charging system on a small aircraft already has redundant safety measures built into it. First off, an ammeter or voltmeter is required so that the system can be visually monitored. The generators and alternators both have breakers that open the output and/or field power circuits if they sense high current flow. And, finally, the regulator power circuit is run through one pole of the typical two pole master switch so that, when the master is shut off while the engine is running, the charging system cannot self excite. Bonus points if you have over/under voltage lights either in your volt/ammeter or connected to your regulator. AND, some manufacturers like Cessna use a stand alone over voltage module inline with the regulator power circuit. Then other manufacturers come along and build voltage protection into the reg itself.

NO BATTERY will with stand the circumstances described in Cathy's response. At some point the operator has to take control and isolate the problem, it can't just be 'ruled' away. Turn off the charging system when you see and over voltage or excessively high current flow. Or maybe when the light comes on to alert you. Don't keep operating with the above conditions present. Don't override circuit protection systems. At what point do you stop blaming the equipment design and just say 'I should turn it off'?

I'm still a fan of EarthX and I'm still installing them. I would like to hear about the Birchwood battery incident, however. Stewartb, could you share the details of this? If you want, PM or call me.

Web
Click to expand...

I interpreted Cathy’s response as pointing out how small the threat is with my installation and that it would an take extraordinary set of circumstances to cause a thermal runaway given the equipment I have. The Birchwood thermal runaway event demonstrates that it can happen but I don’t know anything about that airplane’s charging system or whether the plane had the EarthX trouble light installed in the panel.
 
skywagon8a said:
Web, is it possible for a failure in a system to put out 100 volts? Seems like a big number to me.

and then the EarthX BMS is the recipient of over 100V
Click to expand...

An alternator will gladly put out more than that. The output is based on the field voltage... when regulator is functioning that’s less than half buss voltage. But when regulator fails it may put full buss voltage to field. So it just keeps increasing. Other styles of alternators grounds field to excite it, this style can run away because field wire get damaged and hits/rubs threw to a ground...


Sent from my iPhone using SuperCub.Org mobile app
 
skywagon8a said:
Web, is it possible for a failure in a system to put out 100 volts? Seems like a big number to me.

and then the EarthX BMS is the recipient of over 100V
Click to expand...

I've never rigged one just to measure the voltage, but if it did get that high, I can't imagine the alternator would last for more than e few seconds.

The regulator would have to be completely bypassed and the RPM of the alternator would have to be as high as possible.

Web
 
cruiser said:
http://www.matronics.com/aeroelectric/articles/Alternator_Failures.pdf A generator will self excite. An alternator will, should, not. You need to know your system to know what should happen when you dump the field or master switch during a runaway event.

Credit to Bob Nuckolls of Aeroelectricdotcom
Click to expand...

Correct. However, automotive alternators, with internal regulators, will self excite when the regulator fails to a shorted condition. It's ugly when it happens.

Web
 
mike mcs repair said:
An alternator will gladly put out more than that. The output is based on the field voltage... when regulator is functioning that’s less than half buss voltage. But when regulator fails it may put full buss voltage to field. So it just keeps increasing. Other styles of alternators grounds field to excite it, this style can run away because field wire get damaged and hits/rubs threw to a ground...


Sent from my iPhone using SuperCub.Org mobile app
Click to expand...

Technically it's the current that controls the output. But that's just semantics because higher voltage is needed to increase current flow.

Current flow through the field coils produces a magnetic field. In an alternator, these coils rotate with the shaft/pulley. This means that the magnetic field moves over the output coils to produce power. The regulator samples the output voltage and controls it by adjusting the current flow through the field. In an alternator there is no max current output limit as the output coils of the alternator begin to interfere with each other when you reach rated max current output. So if you had a thirty amp alternator and tried to get it to put out forty amps, it just won't do it. If you keep increasing the load above it's max, the voltage out will start to drop and no higher current out will take place.

Under normal conditions, when you measure the voltage at the field terminal on the alternator, it will NEVER equal bus voltage, even with power to the reg and the engine not turning. I can't vouch for other brands, but the Motorcraft system on the Cessnas usually read between two and three volts when the engine is running. That's all the voltage needed to produce enough current (amps) to start to recharge the battery and run a few lights.

Now imagine a scenario where full bus voltage is connected directly to the field terminal. With the engine running this would be 14.2 volts. And as the output voltage starts to rise, this means the voltage measured at the field terminal also rises. This scenario is a true 'runaway' charging system. The total voltage out will also be exacerbated by the speed of the alternator (engine speed). So if you pull back on RPM's the voltage will not rise as fast/far. But that's just temporary in a true runaway.

Unlike automotive alternator systems, aircraft alternator systems use external power to supply the regulator. This is why power to the regulator power comes from the bus bar, through the field breaker, through one pole of the master switch and THEN to the regulator. This way pulling the field breaker OR placing the master switch off will remove power from the regulator and prevent any further output from the alternator.

Web
 
wireweinie said:
Technically it's the current that controls the output. But that's just semantics because higher voltage is needed to increase current flow.

Current flow through the field coils produces a magnetic field. In an alternator, these coils rotate with the shaft/pulley. This means that the magnetic field moves over the output coils to produce power. The regulator samples the output voltage and controls it by adjusting the current flow through the field. In an alternator there is no max current output limit as the output coils of the alternator begin to interfere with each other when you reach rated max current output. So if you had a thirty amp alternator and tried to get it to put out forty amps, it just won't do it. If you keep increasing the load above it's max, the voltage out will start to drop and no higher current out will take place.

Under normal conditions, when you measure the voltage at the field terminal on the alternator, it will NEVER equal bus voltage, even with power to the reg and the engine not turning. I can't vouch for other brands, but the Motorcraft system on the Cessnas usually read between two and three volts when the engine is running. That's all the voltage needed to produce enough current (amps) to start to recharge the battery and run a few lights.

Now imagine a scenario where full bus voltage is connected directly to the field terminal. With the engine running this would be 14.2 volts. And as the output voltage starts to rise, this means the voltage measured at the field terminal also rises. This scenario is a true 'runaway' charging system. The total voltage out will also be exacerbated by the speed of the alternator (engine speed). So if you pull back on RPM's the voltage will not rise as fast/far. But that's just temporary in a true runaway.

Unlike automotive alternator systems, aircraft alternator systems use external power to supply the regulator. This is why power to the regulator power comes from the bus bar, through the field breaker, through one pole of the master switch and THEN to the regulator. This way pulling the field breaker OR placing the master switch off will remove power from the regulator and prevent any further output from the alternator.

Web
Click to expand...

Thanks, Web, great explanation!

MTV
 
wireweinie said:
I've never rigged one just to measure the voltage, but if it did get that high, I can't imagine the alternator would last for more than e few seconds.

The regulator would have to be completely bypassed and the RPM of the alternator would have to be as high as possible.

Web
Click to expand...

look up converting a car alternator to 120 volt for use in wind generators, basically you install permeant magnets to make it run better at slower speeds... my neighbor built one... don't remember all the details..
 
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N86250 said:
Is it time to mount batteries in an external pod maybe under the gear cabane?
Click to expand...

Way ahead of you! I carry one or sometimes two 8 lb. 11.5 AH batteries for my electric mountain bike in a belly pod. I use 230 watts while riding about 17-18 mph, while also lightly pedaling, so one pack, containing 598 watts (52 VDC x 11.5 AH) can theoretically provide about 45 miles of range. But I'm always climbing mountains (up to 10K, after landing at 7,500') so that sucks them down faster. But "using up" two of them will provide an epic most of the day adventure, and that's why I pack them around, (and assume the risk) they transform what I can do AFTER landing, cold beer being just part of that.


These packs are assembled by a stateside company I trust, using quality Panasonic cells, and with a quality battery management system riding herd over it all. It just seemed like a good idea, and they are also out of the way down there. I have a system rigged up to charge them in flight, at a very low 1.75 amp rate, using a solid state 12 VDC to 58 VDC converter I had custom made. The pack's nominal voltage is 52. The Rotax 912 "lighting coil" (I think that's what it's called, it has no external alternator anyway) only produces about 17 amps, and I have no idea what type of fail safe setup it has to not produce over voltage, so before anyone says I'm crazy for doing it this way, you may be right! But it's worked fine for 2 years now, my second EarthX (been using them for 5 years, recently the aviation specific one, the first one is in my ATV now) resides on the cabin floor between the rudder pedals, surprisingly unused real estate. So, I guess I trust the tech involved in these batteries more then some. I worry more about the gas in the wings, when I worry at all.

FWIW: I got to drive a brand new AWD performance model of the Tesla the other day (0-60=2.9 seconds!) and it's owner, who put over 200K on his first one, and is a real advocate for the car, when I asked about the fleet hours concerning runaway battery issues after crashes, he responded with :"Tesla's have LESS fires then ICE cars, is what the stats are showing". His words, not mine.
 

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If you are really worried about failure/meltdown but want the battery. Mount the battery in the cabin with a simple quick release hold down strap, run the neg and pos cables to a single quick release plug. If it has a runaway meltdown, unplug, release from holder, throw from plane. You may start the next big wildfire but a blazing aircraft would start it also.
DENNY
 
I have attached the schematic of the B&C regulator commonly used in cubs for anyone that might find it useful. A look at the relationship of the three labels on top that show what happens in an over voltage event and drives home the importance of the 5amp breaker between the bus terminal and the bus.

A failure mode of the B&C that I have seen starts the OV event when the output transistor fails shorted. Of course it's quickly followed by the the OV system in the B&C then shorting pin 6 (your bus) to ground. Without the 5amp breaker doing it's job worlds collide. You can test a the B&C for this type of fault by doing a continuity test between pin 4 and 6 if you are in a situation where the breaker trips.

As an anecdote - A friend of mine was kind enough to loan me a B&C with a shorted output transistor that he thought was good. Oddly at idle it did not blow the 5amp breaker or have a runaway voltage event but any addition of rpm caused the breaker to pop. The photo on the bottom is the defective transistor.

Jerry

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This thread made me go out to the hangar yesterday and wire up the warning light circuit that came with my new EarthX (new last spring anyway), as I had never gotten around to it earlier. Not that I felt any increased risk from it, more of "why not, it's right there, and I have a little LED light and the wire." And it's always fun spending quality time laying on the floorboards under the panel, it gets the crimps out of my back! Having the skis on makes this even more "fun".
 
There is a reason why Boeing redesigned their lithium battery box to be made out of a solid billet of stainless steel machined to be 2 inches thick on all sides. That reason resides in that Tasmanian cow pasture.
 
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