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Help me understand the correct battery failure in flight response

lndwarrior

Well Known Member
So I started thinking about emergency procedures and realized something.

I have all the typical emergency procedures documented and carried in the airplane such as Engine Fire in Flight, Engine Failure, etc.. These are all the worst case scenarios - something has already gone horribly wrong.

However they don't deal with "something is starting to go wrong, so what should I do right now?".

These standard emergency procedures don't really address all of the issues and, more importantly, they don't really address incipient issues where you have an indication that something is going wrong and you need to make a decision.

This thought process lead me to the conclusion that I was unprepared for the more likely scenario of, "something is starting to go wrong. What do I do right this minute?"

I decided that the best way to address this in my linear mind was to go instrument by instrument, indicator by indicator and list:

1. System
2. Risk Level to safety of flight (High/Low)
3. Symptom
4. Response

So I'm creating a spreadsheet based on the above. It is a different way of looking at in-flight problems from what I have seen in the past.

I will look at each instrument and indicator in my analogue panel and asses the possible symptoms, what the risk level is for each item and what is the appropriate response.

I think this will be a good exercise to help ensure that I really understand my aircraft.

I decided to do this going from right to left on my panel and assessing every indicator and instrument. The very first one was the EarthX battery fault light.

And right off the bat I realized I did not know the correct response if the light went off in flight.

This light has two indications, one flashing and one solid. The EarthX manual explains what they mean but neither explanation made it clear whether the battery was at risk for immediate failure.

Presumably the solid light would indicate that, but I have emailed EarthX for a clarification. In this case I want to know if it's a "possibility of imminent failure". I haven't heard back from them yet.

Which finally leads me to the question I wanted to post here.

I have an electrically dependent engine due to electric fuel pumps (no engine driven pump). Mags are standard Bendix.

I have an electrical system based on the Aero Electric Z-11 diagram with an e-bus and all the related components on the diagram.

I have a B&C alternator with a VR-166 regulator.

My question is, if the battery fails (and assuming there is no catastrophic damage to the electrical system (ie: the battery electronics safely shut the battery down), will my alternator continue to power my electrical system?

I have heard various discussions about the alternator field wire needing battery power for the alternator to function. I don't know if this is true in my case or not. Is there some other reason why the alternator would not be able to power the system with an off-line battery?

I'm trying to get to the decision point of:

If my EarhtX battery is in danger of imminent failure (fault light is on solid, for example, don't know this for a fact yet). And understanding my plane is electrically dependent,

THEN

A. Do I need to set up for an emergency landing right now, without delay?
B. Am I able to fly another few minutes to a nearby airport and land?

TIA
Gary
 
Last edited:
I have an electrically dependent engine due to electric fuel pumps (no engine driven pump). Mags are standard Bendix.

I have an electrical system based on the Aero Electric Z-11 diagram with an e-bus and all the related components on the diagram.

I have a B&C alternator with a VR-166 regulator.

My question is, if the battery fails (and assuming there is no catastrophic damage to the electrical system (ie: the battery electronics safely shut the battery down), will my alternator continue to power my electrical system?

Z-11 will allow the alternator to continue output, even if the battery (any battery) is disconnected without pilot command, i.e. BAT/ALT master remains ON. The quality of that output (voltage stability, ripple, etc) is an open question and may vary depending on the alternator and regulator choices. I suspect DC electric motors (the fuel pumps) won't care.

That said, Z-11's split or progressive BAT/ALT switch does not allow the pilot to command a battery disconnect and keep alternator output. Opening the master switch in flight will shut down the engine due to lack of fuel.

Wild card; IF a commanded or uncommanded battery disconnect spikes system voltage (I don't know if it will, for sure), the OV module may take the field offline. You'll have a glider.

(Warning: opinion) I think electrically dependent airplanes should meet the same basic criteria as old-school airplanes with mags and an engine-driven pump. You should be able to shut down the airframe electrical without killing the engine. As such, Z-11 as drawn is not suitable for your pump choice.
 
That's the one thing that bothers me about the EarthX - it does have the capability of removing itself from the circuit and to cease providing electrons. With an electrically dependent engine, that is a scary thought. If the battery goes away, will the alternator continue to work? Don't know.

We like to think that 2 failures on a single flight are too rare to happen, but here's one is designed to happen. If you lose your alternator, you transition to battery power only. In theory, you should know how long that will last. But what if you have miscalculated/not checked the reserve capacity or didn't sufficiently reduce demand? Any battery, lead acid or LiFe, will give up the ghost if you keep drawing from it. The lead acid battery will let you know it's coming via falling voltage. The EarthX?

I agree with Dan. You need a backup with an electrically dependent engine, or for that matter with an electrically dependent panel. Some people have backup batteries, some backup alternators, some even do both. Having neither could put you into a bind at some point.

So, as to your checklist item - EarthX battery light on steady - Monitor and prepare to enable battery #2 (which has had its capacity checked recently).

Ed Holyoke
 
Gary,

I offer that your system demand exceeds the capability of the Z-11 type power distribution scheme. Your engine must have power to keep running. Any single battery design fails to achieve a risk tolerance acceptable for this criteria.

Carl
 
If the solid light comes on, or any other indication of failure on any Li-ion battery, I suggest you land ASAP.

I agree that with electric-only fuel pumps, you need a backup battery system.
 
EarthX Manual

In my opinion, the EarthX light is not really a fault indicator. It's really a "pay-attention-to-me" indicator.

You can boil down the EarthX manual to this:

1.... If your voltage is in the normal range (below 15 volts) and your current draw is also within normal range, nothing is urgent. A flashing light just means the cells are balancing. The flashing will stop in a few minutes. A solid light means there's a problem with the BMS (not necessarily the cells) and you should land when you can - not really an emergency.

2... If the pay-attention-to-me light goes on and your current or voltage are high, kill the alternator and land.
 
Battery choice

I plan to put a lifepo4 battery in my aircraft, leaning towards the earthx. I have a mechanical fuel pump and 2x pmags, so I'm not electrically dependent, like you are.

I agree with Carl and Dan that you may want to rethink your design. There are solutions with one battery and two alternators that have been successful (Z-12, Z-13), but these are designed around a "dumb" lead-acid battery that won't turn itself off, no matter what. Yes, it can fail, but it's rare.

I'm not aware of anyone flying with an electrically dependent aircraft with one alternator and one battery, as shown in Z-11. That's probably a bit too risky. I'd go with either Z-12, Z-13, or Z-14. I think today Z-14 with lifepo4 batteries would be fine, not sure I'd use a lifepo4 with Z-12 or Z-13. My personal comfort with them is not quite there.
 
I plan to put a lifepo4 battery in my aircraft, leaning towards the earthx. I have a mechanical fuel pump and 2x pmags, so I'm not electrically dependent, like you are.

I agree with Carl and Dan that you may want to rethink your design. There are solutions with one battery and two alternators that have been successful (Z-12, Z-13), but these are designed around a "dumb" lead-acid battery that won't turn itself off, no matter what. Yes, it can fail, but it's rare.

I'm not aware of anyone flying with an electrically dependent aircraft with one alternator and one battery, as shown in Z-11. That's probably a bit too risky. I'd go with either Z-12, Z-13, or Z-14. I think today Z-14 with lifepo4 batteries would be fine, not sure I'd use a lifepo4 with Z-12 or Z-13. My personal comfort with them is not quite there.

I havent looked at the z-11, but I have one battery, one alternator and two lightspeed ignition systems. so I am totally electrically dependent. I don't see the big risk in this system. I have never had a battery go from operating to zero volts. so I think the odds of having a total battery failure and a total alternator failure are pretty slim. I will add a small backup to run the ignitions, but have not gotten around to it, it is a risk but in my option a very, very small one.

I do however run a lead acid battery, i have no confidence in the lithium batteries at this time. there have been to many problems, and they seem to be a tricky system to keep running happy. I will gladly ive up the weight for the simplicity and reliability of a lead acid battery.

bob burns
RV-4 N82RB
 
I installed a 20 AH back up battery, if I get a primary EarthX battery problem or alternator problem, I shut down the field, then Aux battery On and then master Off. This gives me theoretically 2 hours to run the EFII system but I will land within 30 min and the Dynon backup batteries should keep the EFIS running for 45 min.
 
Your engine has no mechanical fuel pump?

That's a scary thought... a guy here has an -8 and had an internal voltage regulator failure..the voltage spiked to something silly like 30 volts ( I forget what the actual number was), but the battery cut itself off and saved itself. Perhaps a backup lead acid battery could save the day, but then where did all the weight savings go?
 
I installed a 20 AH back up battery, if I get a primary EarthX battery problem or alternator problem, I shut down the field, then Aux battery On and then master Off. This gives me theoretically 2 hours to run the EFII system but I will land within 30 min and the Dynon backup batteries should keep the EFIS running for 45 min.

Brett
Any chance you have a wiring diagram of the integration of the backup battery? If so could you email it to me at gaw dot ebm At gmail dot com?

Tia
Gary
 
That's the one thing that bothers me about the EarthX - it does have the capability of removing itself from the circuit and to cease providing electrons. With an electrically dependent engine, that is a scary thought. If the battery goes away, will the alternator continue to work? Don't know.



Ed Holyoke

Dear Ed,

For clarification, the EarthX battery does NOT remove itself from the circuit for an overcharge situation but continues to provide current while blocking excess current to the battery. This is detailed in the manual on how this works.

For a situation where the alternator is not working/charging, a voltage gauge would alert you that there is no voltage or very low voltage so the pilot is alerted that the charging system is not working properly and that they should consider themselves on battery power only and plan accordingly. For example, while in flight, you should see a MINIMUM voltage of 13.9V. If you are seeing less than that, then something is going on that needs attention, especially in an electronically dependent aircraft. The EarthX battery will remove itself from the circuit when the battery has been drained to around 98% but this is not a surprise event as the pilot would have knows long before this time that the battery is being actively drained and will eventually be out of energy, the same as a lead acid battery and not only would they have a low voltage warning but also the LED fault light would be activated.

Hope that helps clarify things.
 
Shutdown warning?

Howdy Kathy,

I've got the overvoltage protection built in to my BandC regulator, so I'm not worried on that point. What I'd like to know is how much (if any) warning would I get before the battery drops out during an alternator out discharge event. I will get a flashing light from the regulator when the alternator goes offline and will shed amps and will have an estimated time remaining, but have no idea how the EarthX behaves right before it quits. Of course, I wouldn't want to run it down until it does quit, but in the unlikely event that I have no choice but to maximize its runtime....

I know how a lead acid battery acts. The voltage gradually falls off and then falls off more rapidly and the end is near. Is there any such telltale for the EarthX? What will the fault light be doing and how near the time it shuts down?

I'm currently carrying 2 PC680s to make sure my dual EIs and EFIS stay alive post alternator failure. I'm counting on a certain runtime on the first one and then similar time on the one I've held in reserve. When my 680s test below 80% capacity, I would consider replacing one or both with EarthX if I can get comfortable with how they work. I could sure use the weight savings.

Ed
Electrically dependent in smokey SoCal

Dear Ed,

For clarification, the EarthX battery does NOT remove itself from the circuit for an overcharge situation but continues to provide current while blocking excess current to the battery. This is detailed in the manual on how this works.

For a situation where the alternator is not working/charging, a voltage gauge would alert you that there is no voltage or very low voltage so the pilot is alerted that the charging system is not working properly and that they should consider themselves on battery power only and plan accordingly. For example, while in flight, you should see a MINIMUM voltage of 13.9V. If you are seeing less than that, then something is going on that needs attention, especially in an electronically dependent aircraft. The EarthX battery will remove itself from the circuit when the battery has been drained to around 98% but this is not a surprise event as the pilot would have knows long before this time that the battery is being actively drained and will eventually be out of energy, the same as a lead acid battery and not only would they have a low voltage warning but also the LED fault light would be activated.

Hope that helps clarify things.
 
Howdy Kathy,

I've got the overvoltage protection built in to my BandC regulator, so I'm not worried on that point. What I'd like to know is how much (if any) warning would I get before the battery drops out during an alternator out discharge event. I will get a flashing light from the regulator when the alternator goes offline and will shed amps and will have an estimated time remaining, but have no idea how the EarthX behaves right before it quits. Of course, I wouldn't want to run it down until it does quit, but in the unlikely event that I have no choice but to maximize its runtime....

I know how a lead acid battery acts. The voltage gradually falls off and then falls off more rapidly and the end is near. Is there any such telltale for the EarthX? What will the fault light be doing and how near the time it shuts down?

I'm currently carrying 2 PC680s to make sure my dual EIs and EFIS stay alive post alternator failure. I'm counting on a certain runtime on the first one and then similar time on the one I've held in reserve. When my 680s test below 80% capacity, I would consider replacing one or both with EarthX if I can get comfortable with how they work. I could sure use the weight savings.

Ed
Electrically dependent in smokey SoCal

Howdy Ed,

I am copying from the manual below:

The table below shows the recommended user alerts based on voltages when in flight. The low charge level is very different from a lead acid battery, for a lithium battery is completely drained at approximately 11.5V.

Voltage User Alert
>15V High voltage warning (red indicator)
<13.5V Alternator off-line alert (yellow indicator)
<12.6V Low charge level warning (red indicator)


Depending on the battery you choose, as an example the ETX680's have 12.4Ah of capacity (energy) before the battery is drained when new, and as all batteries loose capacity over time, this will decrease and you will test it the same as you would a lead acid battery. If you are using 6Ah of capacity to fly without an alternator working, you would have about 2 hours before the battery is drained. Or if you were using 12Ah of energy you would have about an hour. Please check out our manual as there is 27 pages designed to address these questions and we also have discharge charts too as they are important questions. (www.earthxbatteries.com)
 
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