A Notice to Pilots was issued requiring crews to monitor the battery voltage during APU start and if the voltage was less than 15 volts at any time during the APU start cycle the battery was defective and rectification action taken before the aircraft flew. The technical reason given was that the APU start requires battery power and it is only then that the true condition of the battery is checked.
The true condition of the battery is indeed seen during Apu start as the charger is not in charge mode during apu starts.(NG,not sure about CL).
Are there alternative crew methods of checking the true health of the battery in-flight or on the ground?
The battery charger kicks in when DC is 23v and stops when back to 28v.
The charger cannot go in charge mode during APU start or if no power on transfer bus 1.
So if you want to see if the charger is working too frequently(battery health?),on the ground have the apu on bus and check the DC meter for positive DC Amps,if it does the charger is in charge phase.
Same in the air.
My airline Sop is to keep the dc amp on BAT.
NG has an auxiliary bat and charger just in case
At the end of the day,dont fly into a 63000 ft Storm
