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

[Cactus Charlie]

The voltage plot may be misleading. Voltage sampling started when the load was connected. There is no record of the unloaded battery voltage.

This was the original battery fitted by CubCrafters and the aircraft first flew May 2020. As I have said before I change the ignition battery on condition and test it at runup.

This battery looked very good when in-flight tested but had significantly deteriorated since then. I have all the test data but I'm not going to dig it out now.

Here is in flight test data (ignore the Amps legend that plot was removed):

 

[Neal]

No need to go back for anything. Was just an observation. Most of us only see the charge voltage and don’t know the actual state of the battery. Last night I showed 12.5 prior to start. 13.7 with engine running. Drain down to 12.1 during right ignition backup test and I waited to see where it would stabilize. Realizing plane has been sitting for two weeks.

 

[Cactus Charlie]

Here is the history for that battery. Just had to open the file and capture the image -