Q&A

$300 sound excessive for the normal lead acid battery in your Prius. Yes Toyota have and recognize a problem with the early Prius 12v battery. Their is a bulletin regarding this. Toyota have changed the spec of the battery to a larger Amp hour capacity to prevent the battery draining down in a short period of time. The hybrib battery and systems need the 12v battery for what they call keep alive memory and to initially wake up the computers in the car. 12v operates all the conventional electrical systems in the car.

I have allowed my 2001 Prius (144k miles) to sit for 3 weeks with no problem. I was driving it 40 miles daily at the time. I DID have to replace my battery when I couldn't play the radio for 10 minutes with the 12 volt battery dying, however. I drive daily now anywhere from 5 to 40 miles. The car is made to be driven, and sitting long periods WILL likely cause battery problems.

These things occur to me. #1, be sure the headlight switch is off. The headlight switch automatically turns off the lights when the key is removed and the door is opened. Toyota says to turn this switch off when the car sits for a long time. The switch could be defective but if the switch is off there is no current drain. #2 Be sure to drive the car 50 miles or so once a week. 20 miles might not be enough to charge either battery properly. #3 Put a trickle charger on the 12 volt battery when it sits in the garage. Pep Boys sells a clip set that makes it easy to permanently attach a jack so you can plug in a trickle charger This will cover all the energy drain that occurs with the seven (7) computers that are always running. #4 I pay #160 to replace my 12 volt battery. There is a larger battery available, but if the car is only driven once a week, it may be useless to change to this battery unless alternate charging is available. Hope this helps.