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Ignition backup battery failure on run up - FX3

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Tsquared

Well-known member
Joined
Sep 3, 2020
Posts
106
Type aircraft owned
CCX-2000
Base airport
KMIC
Ratings
Private. Endorsements - Tailwheel and HP
Earlier this summer while performing a engine run up prior to a flight I had the Right Mag emergency backup battery fail.


1787327182622.jpeg

Video taken after aborting the flight and returning to the hangar


The PS-1221S battery had been replaced in October of 2025 during my conditional inspection. Normally I fly my FX3 about 120 hrs a year, but I am down to about 50 hrs a year due to work, weather and an elderly mom who has needed a lot of care recently. Prior to this attempted flight on June 6th, the plane had not flown for 3 weeks and had less than 15 hrs since January. Whether this is a factor or not, it’s worth noting. Also note the battery had a date sticker of 06/20/25 and this failure occurred on 06/06/2026.

1787326146499.jpeg


During the run up the voltage dropped to 5.9 before I shut off the RT IGN Battery. I considered this a failed runup and returned to the hangar for diagnostics.
1787326115011.jpeg


The solution to this was to replace the PS122S battery with a new one. My new SOP will be to replace that battery one year after the battery manufacturing date and not during the conditional inspection time. I have also changed my engine run up check list to include a 10 sec run on the emergency battery.

if you haven't already changed the alerting on for Alternator/Amp to give you a red and audio alert I strongly recommend doing so. This is aligned with what Cactus Charlie recommended in some earlier threads (see the N40DT accident threads and the ignition battery threads).

I’m posting the videos and pictures as most people have never seen (and hopefully never will) this failure before. Hopefully this thread and the other discussions on the ignition system will educate folks and prevent another N40DT situation where the emergency backup system failed when it was needed the most.
 

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