27/02/2013 – Please note the original article refers to a CR2032 battery which is only compatible with the fob for the second generation Prius. The third generation Prius uses a smaller CR1632 battery!
In the last day or two I have found the Prius emitting a single beep when I have parked and turned off the car. Normally, the car will shut off without a sound when I push the ignition button so obviously this was a bit strange.
Anyway, tucked away in the manual I found out that a single beep when turning off a Prius means that the battery in the fob is running low. This made sense as for a while, on and off, the car wouldn’t recognise that I had the key inside the car if I left it on then exited and re-entered the vehicle. Furthermore, I have had the car for just over three years now so it makes sense that the battery would be reaching the limit of its stored capacity.
Anyway, I will be going out to find a replacement CR2032 battery tomorrow and then swap the battery out. Needless to say, you don’t want to let the battery run completely flat as you will face problems getting into the car (although you can use the hidden physical key inside the fob). You won’t be able to start the car by keeping the key in your pocket though so you’ll need to plug it into the fob receptacle to get the car to start.
You can find a replacement battery at shops specialising in automotive products, batteries, general electronics or car fob programming.