2nd Key Fob dead. Where's the battery??

Youtube is your friend:
how to replace prius fob battery - YouTube

 

Any drugstore will sell these batteries, CR2032. You will need one for each fob.

I suggest that you do a search to find out how to replace the fob battery if you can't find that in your owner's manual. This task may not be that easy to do and depends upon exerting some force with your fingers.

Here is my short description:

1. remove manual key - hold key fob with with buttons toward you (key ring to top) - push latch to the left - pull key up and away from you with right hand - remove key

2. turn key fob over (buttons away from you latch on the top) - push latch to the right with left thumb and push whole back cover up with the right thumb -

3. You will need a very small Phillips jewelers screwdriver to remove the four screws that cover the battery once you have removed a trim cover on the fob.

4. remove and replace the battery and screws