"William Sommerwerck" wrote in
:

It condenses on the walls because the relative humidity is high.

It condenses because it's cold.

The air in a refrigerator is very dry. This is one of the reasons
vegetables wilt -- they lose the moisture that "props up" the cell
walls.

Actually, both of you were right, in a way.
The relative humidity in a refrigerator IS generally very high.
But the absolute humidity in a refrigerator is generally very LOW.

Relative humidity is the amount of water vapor in the air divided by the
amount of water vapor the air CAN hold at that temperature when it is
totally saturated with water vapor. Cold air holds less water vapor when
saturated than warm air.

Opening the door brings in air that contains more water vapor than the air
in the refrigerator can hold (the dew point of the incoming air is above
the temperature of the refrigerator) so water condenses on surfaces. Most
of the water condenses on the coldest surface which is the evaporator coil
of the refrigerator (the coil where the compressed freon evaporates,
cooling the coil).

As for batteries, I would expect that some kinds of batteries [Gel cells,
for example] would lose moisture in a refrigerator. I would NOT expect
sealed cells to lose moisture at a significant rate, when stored in the
lower part of the refrigerator, where fruits and veggies are usually
stored.


--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.