New Prius owner here and I have a question about the battery in the FOB - I have the smart key system and if the battery dies, will you be able to start the car? I am assuming that it will work once you plug it in slot on dashboard.
if the keyfob battery dies (smart keyfob or normal keyfob), you can only open the driver's door by the mechanical key, and only start the car by putting the keyfob into the dashboard slot. remote keyless entry buttons will not work, nor will the smart entry and smart start functions.
Instructions are in the owner's manual on how to replace the keyfob battery (CR2032 as I recall). Biggest problem after managing to slide off the cover, is finding a tiny enough screwdriver to open the battery compartment.
The RFID in the fob is passive when placed in the slot, so no battery is required to turn on the car in this fashion. Can we really say we 'start' the car? Well, I suppose if Windows has a START button....