I’m electrically dependent ignition and panel. When deciding between battery and backup alt it came down verifying to the health of my backup battery, what and how am I going to be certain I can count on that backup battery. I knew I was too cheap to replace a couple year old battery that was still good…..
How often are you going to load check the backup battery, and how often are you replacing that backup battery? Complacency rules when everything has been working great and then something goes wrong, will your backup battery have 30 min run time?
In almost 10 years of flying my main alt has failed once a long way from home, my SD8 got me back to Kansas from the East Coast. My Backup alt has also failed but my main alt was working fine. Both times I had an alternator keeping things charged and a battery as a 3rd backup. If both Alternators quit I have my battery to rely on which I view as an emergency situation, hard to verify capacity in the moment………..
-How new and what condition is the battery in?
-Real life load check on battery at beginning of life and end of life?