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Any help much appreciated
Started my Onex with no issues, All systems checked, EMS, Efis, Radio Strobe all worked normally EMS indicated 12.8 volts in system. Did a run up normal after couple minutes EMS indicated a low voltage warning then electrical system shut everything down. I recharged the battery. Next day same thing happened. Checked the battery terminal indicated 2.08 volts, disconnected the battery after recharge Voltage on the Earthx battery was 13.2 volts with good load resistance. All connections seem tight no corrosion observed. All fuzes were good. Any suggestions were to start????

Hey pvs, welcome to the forum. You don't say what engine you have but I'm thinking AeroVee is a good guess. There is not much to the electrical system. You need good magnets, a good stator, a good voltage regulator, and it needs to be hooked up.

When I was troubleshooting I first checked the open loop stator voltage. I think the desired value is in one of the links below. Next I went through a few VRs and the John Deere unit is awesome.

viewtopic.php?f=6&t=7412

viewtopic.php?f=6&t=5977

Good luck!

Need much more information.
At first glance it seems your charging system is off-line. So tell us about your installation. What engine & alternator? How is it wired etc?
I'd expect you checked the obvious (Alt-switch on, all fuses in the system, wires secure)

EarthX low volts is a BMS safety feature. It disconnects the cells when they get too low. A norminal voltage for a charged EX battery is 13.3.

23-27 VAC open loop on the stator at 3000 RPM.
http://www.sonexbuilders.net/viewtopic. ... age#p56060

Thanks to all for the reply. it is an aerovee and is wired per instructions from sonex. it has a mil stratomaster Ems. when I disconnect the negative battery cable battery indicates 13.2 volts. Then after running the engine when the electrical system shuts down the battery indicates 2.08 volts. Disconnect the ground of the battery it indicates 13.2. checked for possible shorts in the can't locate any. How would a charging system come off line after operating normally for about ten minutes. Ant thoughts Thank you

Bryan thank you so much for the links, get to the airport Monday start the quest.

Do the math. If it drops that much after a few minutes, its NOT the charging system. Without knowing more, lets look at a simple example. My two AeroVee's with both ignitions, lights, and instruments draws around 7-8 amps. If I turn the Secondary ignition off, it goes down to around 1-2 but that's not important here. So for easy math, lets we round it up to 10 and guess the battery is a 20 amp-hour battery, it should run everything for two hours. Starting takes a little out of it. So if its charged, we start the engine and run it for less than half hour, without out a charge system, the battery should be at least half charged. I guess that would be around 11-12 volts. NOT 2.08 volts. Borrow and toss an Odyssey in there and see what happens.

I know of about 20 experimental airplanes around me that use Odyssey. A few guys have played with the EarthX ones. The Odyssey guys replace them every three years because the Arizona summer just kills them. Most guys use the 680 in everything from Cubs to 6 cylinders. I use the slightly smaller one in my 3 airplanes and they always make it 3 years. Its $100 but I NEVER worry about them and they always work.

Scott Todd wrote:I know of about 20 experimental airplanes around me that use Odyssey. A few guys have played with the EarthX ones. The Odyssey guys replace them every three years because the Arizona summer just kills them. Most guys use the 680 in everything from Cubs to 6 cylinders. I use the slightly smaller one in my 3 airplanes and they always make it 3 years. Its $100 but I NEVER worry about them and they always work.

I'm hesitant to enter this conversation because I'm not a fan of EarthX batteries and I seem to get excortiated whenever I mention that fact. I agree with Scott here in that putting an Odyssey battery in would likely solve the problem.

EarthX batteries have a BMS that will shut the battery off under certain conditions to protect the battery. In a plane that doesn't require power to run that might be acceptable (still not to me). I don't use EarthX because my Corvair airplane requires power to run and having the electrical system shut down isn't something I can take a chance on.

You need to know what the AC output of the alternator is and what the DC output of the regulator is. I use and recommend the Yanmar voltaage regulator that was referenced earlier.

As for the Odyssey PC-680 only lasting three years ... my experience shows that not to be true. I do buy a new one every three years for my plane (it is electrically dependant so I keep a fresh battery in there). I have placed the older batteries from the airplane in my 1974 VW Beetle, my zero-turn lawn mower, and other equipment. I have one that is ten years old and it's getting a bit on the fritz but most of the ones I have seem to last at least eight years or so and it does get hot here in Carolina too. 8~)

Dale
3.0 Corvair/Tailwheel

I didn't say they only last three years. I said we replace them every three years, like Dale. I've only seen them fail after 4, 5, or even 6 years. But as a precaution, most just replace them. And as a reminder to other viewers, its 120F or more in our hangars in the summer. The few EarthX guys have more battery issues than ALL the Odyssey batteries combined.

Fascinating! The focus on Odyssey, why? They are only a lead acid battery, very much like what you can put in your motorcycle.
If you want to use a lead acid open your marketing befuddled minds and do the research - plenty of good motorcycle batteries out there with all the necessary specifications to make a good choice and at much lower purchase cost.