Your observation of the unhappy timing is probably related to the temperature. Cold batteries have lower voltage across their terminals, triggering the chirp.

Your observation of the unhappy timing is probably related to the temperature. Cold batteries have lower voltage across their terminals, triggering the chirp. (You can troll people into thinking you have magical powers, rub the batteries of a just-failing calculator/scale/wristwatch in your hands and you'll get another ten minutes of use out of them)