MOD Upgrading the ignition backup battery in a Carbon Cub E/FX-3 (EarthX ETX104)

[Neal]

I pulled the battery and it’s on the charger and appears to be taking a charge. Fault light is out.

 

[Cactus Charlie]

The fault light was not on initially

No voltage available to drive it or the BMS.

 

[lrobichaux]

Out of curiosity why are you guys shutting off Master before you go to idle cut off? I’m going cut off before master off. What am I missing?

I have the same question. Please enlighten us.

 

[Neal]

Yes, I go AV and MASTER off prior to shutdown.

As to the last flight data it shows the same as FlySto, it appears my time from AV/MASTER off to shutdown was too fast for the G3X to record. Maybe AXIS records faster

Attached is the last flight prior to yesterday. I checked several prior flights, all data log the same, V1 and V2 read until the log stops.

 

[Cactus Charlie]

That data log stops with engine still turning at 830 rpm. Log samples at 1 Hz. You must have fast hands to get all the power off that quickly.

 

[Neal]

When the engine stops IBBS goes off. When I'm in the hangar I turn it on again to record times.

 

[Cactus Charlie]

When the engine stops IBBS goes off. When I'm in the hangar I turn it on again to record times.

Your choice but you lost data that could have been useful in finding out when the fuse blew. Why not leave it on for a few minutes after engine stop?

If the IBBS is in good condition it will power everything connected to it for well over 2 hours.

Do you have the log that was recorded in the hangar or was there no log for that switch on?

 

[Neal]

I just got off the phone with Keegan at @earthxbatteries tech support and discussed the situation. It seems there is likely a parasitic drain on the ignition backup battery or potentially my amp meter (loop) that was installed, who knows, but sitting for 2.5 months likely drained it. The BMS should kill the battery at 10.8V and that effectively cuts off current to the terminals. It sounds like when I got the charger on it and it rose above 12.8 I think he said that likely cleared the fault light and it should charge back up. We're not sure if there is a failed cell, it is under warranty and I could send it in but I'm going to do a load/capacity test on it and see how that works first.

I then inquired about the new offering coming out. He said it was supposed to release last week but there is a parts supply issue so it could be any day from what it sounds. He is not in engineering but he thinks it's going to be a different form factor like other offerings and potentially in the 8ah realm with a weight of 2 lbs and a simpler design than the other ones we discussed here in other threads or this one. I mentioned to him our need for managing charge current and he didn't have an answer for that but for me to email him to pass it on to engineering.

 

[Neal]

Your choice but you lost data that could have been useful in finding out when the fuse blew. Why not leave it on for a few minutes after engine stop?

Depends on bladder state

Do you have the log that was recorded in the hangar or was there no log for that switch on?

I didn't see it, I updated my local file with everything from the card and checked several files from the last flight date to find that data.

 

[Cactus Charlie]

Back in 2022 I asked Garmin about the conditions required for data logging to start. The answer was -

"The data log begins when at least one of the below criteria are met -

· Have a valid GPS fix

· Engine running

· System is in the air

· Autopilot is engaged"

GPS fix is also important for making screen shots in the hangar. If no fix the files are tagged with date and time starting at system creation date.

 

[Neal]

Load/capacity tester arrived this morning. I'll be using it to load/capacity test both my EarthX batteries. The starter battery should be tested with each condition inspection the EarthX tech support guy mentioned yesterday that some do at annuals. I think it's a good idea.

https://www.amazon.com/dp/B0BWF1429X

I also picked up an Optimate 0.8A charger that will go on the Ignition Backup pigtail for extended periods of non use as recommended by Chat GPT for the charger selection.

I think what happened is there was a parasitic drain on this battery, maybe from my flow meter which will not be reinstalled as it does require power for the display which was disconnected but that circuit was still connnected. The battery being either extremely discharged or BMS disconnected spiked the charge amps blowing the 10A fuse. I think it's wise to keep the ignition backup battery on a charger just like most of us do with our starter batteries. If you're going to ever need to depend on this battery it can't be one that has been sitting nor expect it to be charged up in the duration of any flight in a capacity that it needs to be in order to be used for its intended purpose. AGM's charge slow unlike LiFePO4, don't count on it! The PowerSonic's should be on a charger in my opinion, I've always felt this, and now if I reinstall the ETX-104, which I will if it tests good after the recharge then this will be my procedure now. If there is a parasitic drain on this circuit then your PowerSonic AGM's are toast as well and probably why the health of those have been an issue for many to date. It's a bad design, it's not going to be fixed unless you take action and find a better solution. When I go fly I want my batteries at 100%.

EarthX suggests for storage to disconnect the negative lead which I'll likely do in the future with my RV travels which will be longer duration now. I hate to think of messing with the starter battery leads but I guess I need to disconnect the negative there too. I sure wish there was a battery disconnect switch that was inline on the negative lead.

In my opinion...too many cub owners fly off the seat of their pants like cowboys or something and don't take these situations seriously enough nor prepare for worst case scenarios. Their systems knowledge is not where it should be mainly because there is no training. It's unfortunate, it's a very different world from my Air Force days. No wonder insurance costs what it does, this community is borderline reckless in my opinion and observation.

 

[Cactus Charlie]

In a standard installation any discharge of the ignition battery is blocked by the diode. I am not aware of any possible parasitic drain path.

It may be informative to measure the current draw of your non-standard instrumentation.

The loads on the main battery with master off are -

GPS keep alive 40 uA
Ignition left 115 uA
Ignition right 115 uA

plus anything you left plugged into the 12 V accessory outlet.

 

[Neal]

Very cool gadget for the capacity testing. I got to the hangar, charger showed all green and a good charge on the battery. I removed the charger and voltage checked at 13.2V (or maybe it was 13.3, can't remember). I couldn't figure out how to use the capacity tester as it didn't come with instructions and knew it was going to take some time to do anyways so I brought it all home. I powered on the capacity tester and it provided a bar code which linked to the manual and got it all wired up and setup.

I setup the CC (continuous current) test to use 1.5A to simulate the high side of an electronic ignition demand, realizing the published number I believe is closer to 1.1 to 1.2A. I reviewed the EarthX manual which mentions taking your AH x .8 and divide that by your current which comes out to 2.1 hours so that's how long I let the test run. And in fact around 2 hours and 20 minutes into the test the fault light started a sequence which equates to the voltage the battery was at which was 12.8V and where it starts to signal you of the low voltage. This equates to about 30% SOC.

The battery tests good and will go back in the plane and I will be using the pigtail and a charger going forward as there is no reason not to and it will also prevent the risk of a high charge rate.

Good lessons learned.

 

[Neal]

I ordered the EarthX LED fault light which I'll be installing on the ETX-104. One lesson learned from this is that you have no indication of a battery failure after MASTER is on and after your runup backup ignition tests. So if your battery fails 5 minutes into your flight, you have no indication of that failure. Correct me if I'm wrong.

The EarthX fault light will come on when the battery goes down to 12.8V or has some other type of fault. We don't see the actual battery voltage when the main bus is energized. A benefit of the EarthX with the fault light, AGM users have no indication of a fault until after you turn off MASTER.

 

[Cactus Charlie]

The EarthX fault light will come on when the battery goes down to 12.8V or has some other type of fault. We don't see the actual battery voltage when the main bus is energized. A benefit of the EarthX with the fault light, AGM users have no indication of a fault until after you turn off MASTER.

Do you believe the EarthX internally monitored voltage is isolated from the terminal voltage? I see no indication in the ETX manual that this would be possible.

 

[Neal]

Do you believe the EarthX internally monitored voltage is isolated from the terminal voltage? I see no indication in the ETX manual that this would be possible.

I thought about that. How would what happened to me Thursday be indicated differently. I need to ask EarthX support about that. This also brings into play as to where the LED is wired to come on as it requires power to operate. If I piggy back the 12V (red) lead to something on the main bus, I wouldn't see the issue. I think I need to put it on the USB line so it's always hot, but would that be a parasitic drain on the starter battery, probably yes, that needs to be thought through and probably won't work. Could I power it from the battery's own positive? Then it wouldn't work when the BMS shutoff the terminals as happened in the discharge situation. So this is something that needs thought and I need to talk to EarthX support first otherwise I can see how the LED indicator may not serve its purpose other than a cell fault, not a voltage low warning. In the end, the LED indicator may not work and the only test is the IBBS on VOLTS2 check. Otherwise with main bus power on the terminals you can't get battery health.

 

[Cactus Charlie]

If you had the LED fitted it would indicate a blown fuse and partially discharged battery - but only if the battery still had sufficient voltage for the BMS to operate and control the LED.

You had an indication that the fuse was blown but didn't see it. An AGM user would have the same indication and the AGM user would be unlikely to have a blown fuse.

If you want to know more about what is happening to your ignition battery add a Hall effect current sensor that is not powered by the ignition battery.

I would strongly suggest that no one else copies your installation unless they make provision for charge current limiting.

 

[Neal]

No one should copy anything I do!

What do you think about something like this? Just trying to figure out a way of limiting the charge rate.

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