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Earthx battery experiences

warmi said:
Rotax just released their own Lithium-ion battery to go with their engine - underneath it is just EarthX battery in Rotax clothing :)
Obviously thy do trust underlying technology ….

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With all the charging system/ regulator problem the RV12 has had not sure if I’d be onboard with that!
And Rotax clearly put the operator in the position of determining “certification”.

“The battery is not a part of the Engine Type Design. Lithium-ion batteries
part no. 966260 and 966265 have been tested and released by BRP-
Rotax, but are not certified. The correct function in conjunction with the
entire electrical system is the responsibility of the aircraft manufacturer.
The certification of the battery is the responsibility of the aircraft
manufacturer and must be carried out jointly with the aircraft.”
 
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MElstien said:
For example, if there is a regulator failure, as mentioned on this thread, and the voltage raises beyond a cetain threshold which I think is 16.2 volts for more than 2 seconds, the Battery that is currently on-line will shut down. In that case, one solution would be to turn off the alternator and then run from the second battery while finding the closest place to land. (note, I also will have a secondary alternator with a different regulator set to a lower voltage)
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The BMS will not "shut down" the battery in the sense that you are thinking in the event of high voltage. It will not isolate the battery - it only stop incoming current from going to the battery. If you stop the high voltage event, you can still draw power FROM the battery, you just can't put any more INTO the battery until the BMS resets itself after the high voltage event.
 
airguy said:
The BMS will not "shut down" the battery in the sense that you are thinking in the event of high voltage. It will not isolate the battery - it only stop incoming current from going to the battery. If you stop the high voltage event, you can still draw power FROM the battery, you just can't put any more INTO the battery until the BMS resets itself after the high voltage event.
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Exactly correct, the battery protects itself - but that is not the point.

If the battery stops incoming current during an over voltage event, the voltage spike still happens but now there is no battery to cap the voltage excursion it as would be the case for a dumb lead acid battery.

As I said, do not assume your alternator over voltage protection will save your very pricey avionics. Test the system to see at what voltage it trips the alternator off line. A good reference is section 6 of “The Aero-Electric Connection”.

I also suggest a system design that has a common POH immediate action for any electrical fault. Beat this into your head as a bad over voltage excursion can happen very fast. In my plane that action is open both master solenoids, then evaluate. My panel gets power via separate feeds from each battery - the result is the panel is still up for a 2-3 hours but the alternators (and associated fat wires) are isolated from the battery.

As been discussed, the EarthEx has a lot of capability that makes it attractive for our planes. As the builder (and system designer) understands it’s limitations as well as it’s advantages.

One last comment. Please carefully document your wiring, connections and equipment integration. You will make life much easier for those who get your plane when you are done with it.

Carl
 
I’ve been using the earthx batteries for many years on both mine and our customers airplanes. Their support has been stellar, even when the battery failure was caused by the customer. There’s a post in the forum somewhere where I compared the odyssey battery to the earthx and the results were amazing, especially the difference in cranking speeds and reserve capacity. I use the 1200 in the RV-10.

As has been mentioned, they do need to be cooled if placed on the firewall.
There are lots of potential failure scenarios for both types of batteries. Most of them that I have seen come down to bad wiring or poor alternators.

One wiring bad practice that I consistently see is routing the field wire parallel and cable tied to the main B lead from the alternator. If the field wire ever chafes through the big wire, the alternator voltage will spike very high and very fast. The only way to stop it is to pull the alternator CB, as your field switch is no longer effective, due to the downstream short. Yes, it has happened. You might check yours.

Vic
 
Carl and Walt both have very valid points - you want to have a WORKING (that means test it!) over-voltage device to drop the alternator field current offline, and you want to make sure a short like Walt refers to can't happen. If the field wire is energized via a short to the B-lead in the FWF area, the alternator will run away and there is no way to control it unless you have a B-lead breaker (and not many folks have one of those) to isolate that before it gets onto your power buss. The commonly seen ANL fuses will burn away if this occurs feeding a lead-acid battery, as that battery will accept the overvoltage and boil its life away while pulling enough amps from the alternator to eventually blow the ANL. With an EarthX battery and the BMS taking the battery off the charge circuit, that same runaway alternator will spike in voltage, but with no place to put it, not nearly enough amps will flow to worry that ANL fuse, so it will stay connected. That could result in letting the magic smoke out of your high-dollar boxes.
 
Carl Froehlich said:
One last comment. Please carefully document your wiring, connections and equipment integration. You will make life much easier for those who get your plane when you are done with it.

Carl
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In my case with a stone age basic super simple systems I prefer, practically anyone who knows anything about electrons could figure it out.
Multiple relays-no, multiple bat busses/bus switches-no, diodes everywhere-nope.
Some fuses and CB's tied to a single bus, easy-peasy, simple, reliable.
Except for the constant fear of exploding lead acid batteries of course, o_O
 
vic syracuse said:
One wiring bad practice that I consistently see is routing the field wire parallel and cable tied to the main B lead from the alternator. If the field wire ever chafes through the big wire, the alternator voltage will spike very high and very fast. The only way to stop it is to pull the alternator CB, as your field switch is no longer effective, due to the downstream short. Yes, it has happened. You might check yours.

Vic
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Not sure I agree with this, bundling wires is a pretty standard thing, the real problem is the installation, not the fact that it's bundled together.
 
airguy said:
… If the field wire is energized via a short to the B-lead in the FWF area, the alternator will run away and there is no way to control it unless you have a B-lead breaker (and not many folks have one of those) to isolate that before it gets onto your power buss. The commonly seen ANL fuses will burn away if this occurs feeding a lead-acid battery, as that battery will accept the overvoltage and boil its life away while pulling enough amps from the alternator to eventually blow the ANL…
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I have a different understanding:
  • Let there be a 60A alternator and 60A ANL current limiter.
  • Assume the 60A alternator can exceed its rating by 20% so 72A. I believe this is conservatively high in this context. An alternator cannot exceed its rating by a great deal fundamentally because the materials in its magnetic circuit saturate. Ref Balmar curves for example.
  • A Bussmann ANL current limiter placarded at 60A will carry something over 100A indefinitely, maybe 120A, eyeballing the ”Time-current curves – average melt”.
BTW I’m aware of an RV that purportedly had the B and field wires short together:
  • Pilot didn’t/couldn't pull B lead CB, all electronics destroyed.
  • Sorry I don’t know the CB rating or battery chemistry.
  • My point is the pilot didn’t/couldn’t to pull the B lead CB. Walt points out below that “Most 60 amp breakers cannot be pulled!”… I didn’t know that, thanks!… I’m using a Littelfuse 100A MIDI fuse.
  • Obviously best to craft the installation so shorting of B lead to field wire is impossible. And to periodically test OV protection.
 
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Walt said:
In my case with a stone age basic super simple systems I prefer, practically anyone who knows anything about electrons could figure it out.
Multiple relays-no, multiple bat busses/bus switches-no, diodes everywhere-nope.
Some fuses and CB's tied to a single bus, easy-peasy, simple, reliable.
Except for the constant fear of exploding lead acid batteries of course, o_O
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Or the constant fear of everything else…

That’s ok, though, everyone has there own level of risk aversion…
 
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