Has anyone tried the PriorityStart? Can this be an answer to the dead 12v battery problem? PriorityStart - Stop Dead Batteries on Cars & Boats [Priority Start! Battery Protector] The cost is around $90 from the manufacturer but they are available for less than $40 on sale. Not a bad price if the will work on the Prius. I have no interest in this company, I just ran across it in an AutoSport sale catalog.
It doesn't look like the automatic reconnect feature will work with the Prius. It looks for a load on the system to cause it to reconnect the battery, but that will only work with simple mechanical switches. Most of the Prius electrical system is controlled through electronic controllers. You might be able to work around it, but I wouldn't expect it to work right out of the box. Tom
+1 The answer to a weak 12 volt battery in a 4 or 5 year old car or if the battery has been mistreated by allowing it to run flat several times is to replace the battery with a new one and send the old battery to the recyclers. It's no secret.