Hello just bought a 2005 Prius fully loaded with 115,000 miles. I have the service records and Carfax, and all checked out good. All recalls have been done, as well as all maintenance scheduled intervals. It's been driving good for a week now. Have a question though. I did a check of the 12V battery yesterday to see how it was health wise, and the volts dropped quickly to about 9 or 10 volts I believe. I could not find a record for it's replacement. Now just today after filling up the tank the center screen is giving falls readings for mpg. Is this a result of a possible failing 12v battery. No warning lights are on. Thanks.
If you've done enough research on how to get to the diagnostic screens to check for battery voltage than surely you know enough to know that a 10V reading is a clear indication that you need a new battery so I don't understand what thoughts you are trying to elicit here?
Just trying to get some opinions is all. I reset the mpg screen and now it seems to be OK. I took the car for about a 20 mile trip and the mpg screen appears to be working correctly. Before the reset it was showing, at times, full charging bars, not the usually one less bar at the top. Sorry if I am not explaining this correctly I am still a Prius Newbie ha ha. Also I ran a diagnostic check in full power on mode and the 12V battery showed a consistent 14.0V. But since I don't know the age of this battery I'll have it replaced or do it myself.
I have an '05 with about the same mileage and I replaced the battery about a year and a half ago just as a precaution. After I removed it, I checked the amp-hour capacity and it turned out to be about 70% of new. I might have eked out another year or two of use, but given the normal lifetime of these batteries I decided to change it at my convenience instead of the battery's convenience, which most likely would have been on a cold, nasty morning. Richard
be sure to check out my post on how to get an Optima for $126 + tax, it increased your fuel economy, lasts twice as long as the stock battery and is not as susceptible to being damaged if accidentally fully drained (such as leaving a light on or door ajar for a few days)
