Paul Slocum

The other day the car started fine, we drove about 20 minutes, and then
electrical devices started failing: first the speedometer, then the air
conditioner fan, the windows were slow, and after another 15 minutes
the car died (while driving on the highway) and the battery was too low
to start. There had been no previous problems.

The dealership is telling me we need a new battery, but there's no
problem with the electrical system or alternator. Is this possible?

thanks in advance,
-paul