What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

ETX680 flashing fault light

I've just commenced test flying on my RV8 down in Australia. I've got an IO375 with the System 32 EFII, a plane power alternator and an ETX680 main battery. The engine is new so the priority is to run it hard and it does get a little warm - CHT's around the 400 degree mark. On the second flight the brand new alternator failed by blowing the field fuse around 20 mins into the flight. Analysis of the G3X data shows that it was producing just 13.2V and just enough current to drive the base load - about 14A when it failed. The same thing happened on the next flight after the fuse was replaced. The alternator was replaced with a serviceable item and 20 mins into the next flight, I got a flashing BATT caution (5 sec flash, off 5 sec), courtesy of the G3X. I landed and investigated and did some homework on the fault light interpretation (possible cell imbalance) and decided to get airborne again to fault find. Before I did that, I charged the battery with the smart charger and it came up clean with no abnormal indications. After about 20 mins, I got the BATT light flashing with normal voltage (14.2V) so I turned the alternator off. After about a minute, I turned the alternator on again with normal indications. After a further 15 mins, the BATT light flashed 5 sec on then off again so I turned the alternator off again for 10 seconds this time and then on again and the system gave normal indications for the rest of the flight. Before anyone criticises my airmanship, this was done over the field and the battery lives in a sealed, ventilated compartment . Has anybody seen anything like this with the ETX680? While I think the alternator issue and the battery issue are separate, they are part of the same system and have happened in a sequence and I wonder if the faulty alternator has somehow affected the battery. The electrical system is lifted straight out of the AeroElectric connection and there's nothing fancy at all going on. The ETX680 cranks the engine like a dream but as soon as the engine fires up, the alternator is using all of its (60A) capacity to charge the battery right away which doesn't seem like it should be good for it. Is there some way to tone that down? Does anybody have any thoughts? Thanks in advance.
 
Due to lithium batteries having low internal resistance, they will accept all of the charging current that the alternator is capable of putting out. If you want to limit the charging current, put a diode in series with the alternator output ("B" lead). Of course the voltage regulator needs to monitor system voltage upstream of the diode. That will not be a problem with alternators with internal voltage regulators. A bypass switch could be installed in parallel with the diode. Closing the bypass switch will eliminate the voltage drop across the diode.
I am not necessarily recommending the installation of a diode or switch, just offering a way to "tone down" the charging current.
Another way would be to limit alternator field current for a certain time period after engine start.
 
I had similar problems.

I'll be the first to say it - call Kathy at Earthx. If she doesn't know, and she probably will, she will get you the answer as to what is happening with your battery. I suspect you will have to replace it. There are some events that the Earthx will not recover from.
 
EarthX Battery Fault Matrix

Chris,
To be sure you're aware of the EarthX's fault matrix, here it is from the ETX series manual. The fault light will either flash fast (overtemp), flash slowly (other problems, voltage-dependent), or come on steady (BMS or short circuit). I pasted this page in my POH.

So note that the slow flashing fault's diagnosis is coupled to the indicated voltage.

Which set of symptoms did you have? Solid light or fast/slow flash, with what voltage, and how long did the light flash?

I'll be the first to say it - call Kathy at Earthx. If she doesn't know, and she probably will, she will get you the answer as to what is happening with your battery. I suspect you will have to replace it. There are some events that the Earthx will not recover from.

That's very fine advice.
 

Attachments

  • ETX Fault Matrix.jpg
    ETX Fault Matrix.jpg
    165.4 KB · Views: 108
Cathy at Earth X is great to work with. The 680 has a maximum charging limit of 60 amps. I’ve seen some alternators rated at 60 amp output more than that. The Earth X batteries seem eager to accept higher amperages when discharged. If I need to run the batteries for more than a few minutes (software updates) I make sure I put them on the charger overnight. I used the ETX900’s in my 14 just to give a little more battery life and to increase the max charging rate to 80 amps.
 
Thanks everyone for your input - I spoke to tech support at EarthX and they agreed it was a cell balance problem based on the symptoms/matrix and they're going to replace the battery.
 
That's great to hear. Thanks for posting the conclusion too. Good to hear about good customer service.
 
Back
Top