problems starting 2007 Prius Intermittenly

Given the need to repeatedly jump start your car, there's around a 95% chance replacing the 12V battery will solve your problem. I suggest that you do that and not worry about trying to test the battery first.

If you go to the dealer to have it checked, you will probably be charged for one hour of labor. Why pay $100 to be told that your battery is weak? Use that money to help fund a new battery purchase and be done with it. (A new battery at the Toyota dealer's parts counter should cost ~$135 or so.)

A low voltage reading will tell you that the battery is bad. However a high voltage reading (if the battery is not under load) does not necessarily mean the battery is good.

 

I figure $140 for a battery is pretty typical, and isn't the Prius battery a dry type (and aren't these more expensive)? Patrick?

 

$211 is an OK price if that includes dealer labor to install. The Prius battery uses absorbed glass mat technology, so there's little or no liquid acid in the case. That type of battery tends to be more costly than a traditional liquid acid battery of similar capacity.

 

I had a similar problem with intermittent starting, however my car had 12v or not. It could always be jumped, which I got pretty good at. I thought I had some slow drain on the battery. But then I noticed that it happened more frequently when I parked on a hill, drivers side downhill, think not level left to right. Curious I went back to the battery and was determined to follow the ground. The connector on the battery negative post was very tight, but I found the other end which grounds to the chassis was free to slide around under the retaining bolt. I tightened it with a 10mm socket. so far my problems have subsided. The ground cable is about 8” long and grounds to the chassis right by the passenger rear tail light. My Prius is a 2007.

 

I forgot to mention that prior to this I was having a problem with the brake system upon startup. If you started the car and put it in gear(either fwd or reverse) the car would leap about 3-5 ft. In hindsight, this was due to the brake pump not having a solid 12v supply. Since I found the grounding issue, I no longer have the problem with the car lurching forward. It makes sense now, but at the time the cause of more bewilderment. My car is super reliable again after fixing the 12v gnd issue, which was the cause of a few other problems.