The back-up battery on my 5600 PFD is about 2 years old and I am wondering if it needs to be replaced.
When I shut off the master switch the 5600 will power down over about 30 seconds. It is displaying the back-up battery voltage which is never above 12.1 volts but then drops within the thirty seconds to 9 volts. This suggests to me that the 5600 will only run for 2-3 minutes before the low voltage limit of 8 volts will be reached.
The manual describes a process to keep the 5600 running on the back-up battery on the ground. Is this a reliable way to test how long the 5600 might run on the backup battery if external power is lost in flight? A rough estimate will do. I don't care if the 5600 runs for 50 minutes instead of 60, but only 3 minutes is pretty short...
Thanks
Keith