Over voltage required for EarthX battery

[airguy]

Originally Posted by vic syracuse

Here you go:

http://www.vansairforce.com/communit...=Earthx&page=7

Thanks Vic - spent the last hour doing a bunch of reading. I may not be a convert yet, but I'm at least considerably less of a skeptic.

[444TX]

Originally Posted by scrollF4

George,
It looks to me that you and EarthX are in agreement. Both of you seem to be saying the charging system must have overvoltage protection to open the circuit and protect the ship's systems (not just the battery) if the voltage spikes dangerously. This is accomplished through an internal or external voltage regulator with overvoltage protection (crowbar) or a specific overvoltage protective function in Vertical Power-Pro VPX. EarthX is saying that we builders absolutely need this protection...that it needs to be a non-negotiable requirement in our systems' design.

In that, you two seem to agree (as do many others in this thread), and that's a good thing.

---------------------------------------------------------------------------------------

I do not agree. Maybe the battery went open first, for some as of yet unknown reason, then the non-high voltage protected charge system went full field with the resulting high voltage.

Why did the battery, which should have been protected internally, get hot?

If we are protected from overvoltage and have an open battery we have no electrical system. There are possible scenarios here that can be bad in an IFR electrical only aircraft.

Again. Do not agree.

George Meketa

[scrollF4]

OK, George, sorry, I didn't understand you correctly.

[DanH]

Originally Posted by 444TX

Maybe the battery went open first, for some as of yet unknown reason, then the non-high voltage protected charge system went full field with the resulting high voltage.

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..

Why did the battery, which should have been protected internally, get hot?

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

[444TX]

Dan H

Are you are speculating, maybe correctly, but still speculating on the internal disconnect? What testing has been done to prove this? There is a failure mode here that the manufacturers initial data does not explain. We now have a "fix", or do we.

There have been two recent documented failures, both systems having no overvoltage protection. Maybe this is coincidence? Even with protection would the lights have been out? Many RV's have flown for twenty years without it and without problems (I feel it is necessary), maybe the battery is part of the problem.

Even Boeing, with their billion dollar engineering budget did not get it right. There is a lot of work to be done and time testing before one of these lithium batteries should be used casually. I feel, at the moment, the risks involved with using one as the main battery in a non-regimented testing type environment are too high, especially IFR. Sealed battery boxes, temperature measurements, outside the cockpit for safety, etc. Measures and measurements should be taken.

I have a lithium E-bus backup battery that in normal flight is isolated from the electrical system until needed, along with a set of scenario based procedures to deal with electric system failures. There are some foreseen lithium risks involved but, unless I missed something, they are manageable. So, I am not scared of change. Just careful.

Like yourself, I go out and try new things with my eyes and mind wide open to the risks. You and I both understand what we are getting into. We test, identify, isolate, plan for, and managing the risks. Others here just follow the trends and have no idea of the risks they are taking. I feel that you do a great job showing all the things you have done on your plane, but do not make it clear that many things may be on the edge for others to blindly follow.

Like load dumping and running your alternator with no battery? Just because your system can do it does not mean another system with a different alternator, system load, regulator, wire sizing, overvoltage protection, battery, etc. will do the same thing. Just changing a battery with one of the same model with upgraded internal circuitry could change everything and not work the same as previously tested. Please make this clear.

We are on the same team, lets work to make flying these planes safer.

George


George Meketa, RV8
B&C alternator, ford voltage regulator, PC680 main battery (for now), crowbar overvoltage protection, 1700 hours

[rv7charlie]

Yes, you can get an 'Amen'. Well said; better than some of the rest of us have been able to articulate.

Charlie

[ChiefPilot]

I've been watching this with some interest, and the thing I keep thinking is that crowbars and such are great (mine has one), shouldn't there also be some kind of annunciator to show the out-of-range voltage condition? I both see it and hear it on mine, and I doubt that the several seconds it'd take me to disconnect the alternator would have much of an impact on the battery (I did test a Shorai LiFePO4 battery to destruction; it required over 15 mins to bulge and start outgassing when exposed to an overvoltage condition).

Shouldn't an over-voltage annunciator be a part of the list as well?

[Fast Eddie B]

Does anyone market a self-contained over-voltage indicator?

I?d be interested in one for my Sky Arrow.

[DanH]

Originally Posted by 444TX

Dan H Are you are speculating, maybe correctly, but still speculating on the internal disconnect? What testing has been done to prove this? There is a failure mode here that the manufacturers initial data does not explain.

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

There have been two recent documented failures, both systems having no overvoltage protection. Maybe this is coincidence? Even with protection would the lights have been out? Many RV's have flown for twenty years without it and without problems (I feel it is necessary), maybe the battery is part of the problem.

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.

Even Boeing, with their billion dollar engineering budget did not get it right.

Different battery chemistry.

Measures and measurements should be taken.

Always.

Like load dumping and running your alternator with no battery?

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.

[DanH]

Originally Posted by ChiefPilot

I've been watching this with some interest, and the thing I keep thinking is that crowbars and such are great (mine has one), shouldn't there also be some kind of annunciator to show the out-of-range voltage condition?

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.

If you don't have that capability, recall I found a nice little stand-alone voltage monitor. Cheap as dirt and works very well. I'm using one to monitor IGN2 battery charging. If voltage goes above or below user-defined limits, it lights a flashing LED on the panel.

https://www.tomtop.com/p-e1021.html