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

[Neal]

I have two spare fuses once I learned of that as well and keep it in my spares kit.

Okay, I returned to the plane today for more ground run testing.

1) Pulling the emerg ignition breaker drops the voltage to 0 in the GDU

2) Pulling the inline fuse at the battery positive does nothing to the GDU

I need my clamp meter to measure amps for the charge, I looked at buying a mini meter with a display or a bluetooth option which would require a shunt install like in my RV but decided not to.

AMPS today during the ground run did not exceed 11. I will never be in a condition where the starter and/or ignition backup are not in a nearly full state of charge. With pigtails on both, they will be maintained and charged after any period of non use.

I've decided to call this MOD done. I'm staying with the EarthX ETX104. I will fly with the right forward panel off a few flights to monitor for my own comfort, both the electrical but also my mount solution.

 

[Cactus Charlie]

1) Pulling the emerg ignition breaker drops the voltage to 0 in the GDU

That is unexpected and seems to be in conflict with the published schematic.

IGN VOLTS is sensed at ignition switch terminal 5 by wire A11A20O which feeds the GEA 24.

With ignition switch Off terminal 5 is connected to the battery via switch jumper 5-3. Terminal 5 should see battery voltage when the ignition CB is pulled.

2) Pulling the inline fuse at the battery positive does nothing to the GDU

As expected since, with switch Off, switch terminal 5 is connected to switch terminal 4 and reads MAIN bus volts when the fuse is missing.