Remarkable MPG increase after 12v battery

Discussion in 'Gen 2 Prius Fuel Economy' started by PriusGuy32, Sep 27, 2012.

  1. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Ok I read about replacing a bad or ailing 12v battery (mine was original - 2007 - and resting at 10.1v) and an increase in mpg's. But I didnt expect this kind of increase! :love:

    I bought the car 9-14-12 and had been driving it very hypermilishly...lol...and getting 48mpg average.

    Replaced the 12v battery Sunday, filled up and now Im getting 52mpg and it actually has gotten COLDER since the 48mpg tank. (y) Every morning has been ~40 degrees F. I also notice that when Im cruising down the road at 50mph, my instant mpg's are much higher.

    Im stoked. And its true what others have said - check your 12v resting voltage and replace it if its time, you will gain mpg's. Good time to check right now because its getting cold!
     
  2. hill

    hill High Fiber Member

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    Ain't it great when you follow PC folk's directions and it pays off.
    ;)

    SGH-I717R ? 2
     
  3. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    YES :cool:

    And by the way, its been 2 weeks and I dont miss the Envoy I sold ONE BIT. Every day I come home, I tell the partner "Did I tell you today that I really LOVE my new car?" lol. I think they're sick of hearing it :D
     
  4. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    In some failure modes, the 12v battery is constantly charged by the inverter to no avail. This wastes energy that could have powered the car down the road. Other 12 volt batteries will fail in ways that do not reduce MPGs.

    So it is possible to have a dead 12 volt and not have your MPGs improve after replacement. But it is nice, as you feel you paid for something that saves you money down the road..
     
    PriusGuy32 and uart like this.
  5. uart

    uart Senior Member

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    Fantastic! Now you'll just have to wait for spring and you'll probably be getting 55+ MPG. :)

    Yep, and with the OP's battery at 10.6 volt it's a pretty bad case so some sort of improvement was at least fairly likely. Where a problem arises is when someone is getting around 11.8 or 11.9 volts at Ig-On and they change the battery because everybody tells them what a huge difference it will make. And then they end up disappointed when nothing happens.
     
  6. Adam Leibovitch

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    haha, awesome! I have a PiP now, but I remember when I changed the 12v a little over a year ago my mpg went back up to 43. Had fallen to 40 over the few years. I did absolutely no active driving, just drove how I normally do.
     
  7. CaliforniaPrius

    CaliforniaPrius Active Member

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    How much is your new 12v battery?
     
  8. Thadd Dale

    Thadd Dale New Member

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    Has anyone done the battery conversion to the civic large post battery? It's only $60
     
  9. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    Is the Civic large post battery both AGM and externally vented?

    Your Prius 12 volt battery is in the passenger compartment with your loved ones. AGM (Absorption Glass Mat) have less free sulfuric acid to fly around the cabin in the case of a wreck or explosion. Externally vented batteries do not let hydrogen (an explosive gas) or sulfuric acid mist build up in the passenger compartment. Many batteries work in the Prius electrically and dimensionally, but once you factor in the safety of your passengers (and yourself) only 3 batteries seem wise.

    The OEM battery sold by Toyota
    2009 TOYOTA PRIUS Parts - Champion ToyotaWorld
    A Optima yellow top designed just for the Prius
    Optima DS46B24R Optima battery direct fit replacement for Prius 2004 + with Instructions
    And an Exide battery
    Toyota Prius Starting Battery - Exide Edge 51JIS Flat Plate AGM
     
  10. Thadd Dale

    Thadd Dale New Member

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    yes the one I was looking at is AGM the posts are larger so you must replace the ends nut its much cheaper than the prius battery.
     
  11. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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  12. CaliforniaPrius

    CaliforniaPrius Active Member

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    so you are saying 48 to 52 mpg?
     
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