1.5 v battery aaa voltage dropped to 1.286 still usable ? -- nah

 quote here

AA batteries start off with 1.5 volts of energy, but the voltage goes down as the batteries are used up. Once the batteries dip below 1.35 volts, they appear to be dead, even though they still have a lot of juice left

https://money.cnn.com/2015/06/02/technology/make-battery-last-longer-batteriser/index.html

For 1.5v AA or AAA primary batteries, 1.3v "under load" as tested by your DMM is considered dead. For 1.2v Nicad or NiMH AA or AAA rechargeable batteries, 1.0v "under load" is considered dead.

--- from another internet source https://www.candlepowerforums.com/vb/showthread.php?216433-At-what-voltage-are-alkalines-considered-dead