Video explains how to check if your battery is going bad in a 2004-2009 Toyota Prius. Please see my other video on how to change the 12V battery since it is a little more in depth than a normal 12v battery. (http://www.youtube.com/watch?v=P5sD1zepGQY) Some dealers will charge you 300 bucks to change a Prius Battery. With a little knowledge you can do it for free plus the cost of the OEM battery.