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

[Cactus Charlie]

Wouldn’t it be nice if the backup ignition switch was just an arming feature? In fact how about removing it and the ignition fails over to the backup battery when voltage drops below a level? Sense alternator and starter battery voltage. When insufficient then engage backup ignition. Make the switch an override only. It should never need to be touched.

When I was designing my TCW IBBS installation that will, one day, replace my 2 AH AGM I considered 3 switch options:

OFF ARM
OFF ARM ON
OFF ON

I decided on OFF ON keeping the switch functionality the same as the CubCrafters design.

There were several reasons for this choice -

It keeps the existing switch and placard
It works the same as any other FX-3
It can be tested without needing a breaker pull
It keeps the same LED warning lamp and it is functional with Master off

An auto ARM function must be designed so there is no drain on the ignition power source when Master is off when not in flight. That pretty much forces a switch with an OFF position and a light to warn when On.

 

[lrobichaux]

Please don't enable me. I want to upgrade to the 1200 but don't see that it's necessary haha.

OK, let's clear up any misunderstanding ... since when does something need to be "necessary" before we spend money on an airplane?

I'm waiting for my 900 to show even the slightest degradation so I can break out the credit card

Now this is the correct mindset.

Wouldn’t it be nice if the backup ignition switch was just an arming feature?

This is the way the CCX-2300 is designed. The (R) backup battery switch is a 3-position switch - off, auto and on. Auto is "armed" where so long as main bus voltage is normal, then it's my understanding that it "passes through" the (R) back-up IBBS unless and until main bus voltage drops below normal level. If that happens when the switch is in "auto," the (R) back-up IBBS automatically begins powering the (R) ignition and (L) ignition continues to be powered by the main bus / battery. Not sure if this can be designed into the FX-3 panel / system, but should be a simple question to investigate.

 

[Cactus Charlie]

Not sure if this can be designed into the FX-3 panel / system, but should be a simple question to investigate.

I did investigate this option and decided against it. That does not mean it could not be done.

 

[Cactus Charlie]

Another one bites the dust. This one, which was not PowerSonic, was useless after 9 months.

 

[Neal]

Now imagine how many out there don't know that their ignition backup battery is bad. And how many aren't changing them annually? Yeah...scary. I need to get that forward right panel open and start working on my mod.