Carbon Cub EX-3 Engine Failure (N40DT)

[Cactus Charlie]

I have chosen to use 11 V as the self isolation voltage.

EarthX replied to my question about self isolation voltage of the ETX680C -

"It will disconnect right around 10.8 volts depending on how much load is on the battery."

 

[Neal]

It's up to the NTSB as we know to look into all of that but we can all learn from accidents. It is normal in the Air Force (military) to study accidents and learn from them. It's apparent in GA no one wants to learn from accidents and just be cowboys. Very disappointed in some recent handling of this matter which I'll share someday in the future.

I'll check the diagram you pointed out, thank you. I just like the see the guidance in black and white. I know Klaus mentioned in the past the installation is not done per the manual such as with shielded grounds, etc. when digging into my coil pack failure saga. I get it that there are variables such as space available, size, weight, and climate that need to be factored into this battery decision.

 

[Neal]

Posts have been moved out of this thread to a new thread on topic of backup batteries for electronic ignitions so this thread can remain on topic of the accident and any lessons learned. For backup battery discussion please use:

Thread 'Choosing an ignition backup battery for an electronic ignition piston aircraft engine'

Oct 11, 2025

This thread is created to continue the discussion from this CubCrafters Carbon Cub EX-3 thread that had an engine issue and presumably defective ignition backup battery. It created a discussion on the suitability of the PowerSonic PS-1221S 2AH battery used by CubCrafters. Several are discussing options for a better replacement that aligns closer to what Light Speed recommends of a 4.5 AH battery size and also methods for testing the backup battery.

Posts below are being moved out of the referenced thread above into this one to keep the other thread on track with the accident...

• Neal
• Replies: 20
• Forum: Engines and propellers