I am thinking of getting a Prius but have one concern. I will need to store the car in an unheated garage for 4-5 months every winter. During that time, the car won't be used or started at all. I am wondering what effect that will have on the battery. Has anyone done this?
Toyota TSB PG007-03 suggests that a stored Prius should be placed in "READY" mode for 30 minutes every two months to charge the hybrid system traction battery and the 12V auxiliary battery. In addition, when the Prius is stored for more than 10 days at a time, Toyota suggests that the 12V auxiliary battery be disconnected to prevent parasitic drain.
If the traction battery has discharged, it will be necessary to have your car towed to the dealer, and you will have to wait until the dealer can get hold of the special charger used to charge the traction battery. Apparently Toyota only has one of these chargers per sales region.
If you must leave your car unattended for 4-5 months in the winter, a Toyota hybrid is not the right choice for you.