1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Poor MPGs following Battery Swap

Discussion in 'Gen 2 Prius Main Forum' started by moshe_levy, Jan 21, 2012.

  1. moshe_levy

    moshe_levy Junior Member

    Joined:
    Aug 13, 2007
    62
    7
    0
    Location:
    NJ
    Vehicle:
    2008 Prius
    Model:
    N/A
    All-

    Swapped my dead OEM battery for an Optima a few days ago. In the 200 miles since, I'm averaging 27.3 MPG according to the computer. Usually I'm in the 40-41 range as I do alot of highway. I'm wondering if there is some resetting or reflashing I'm supposed to do when swapping a battery - for example on my motorcycle, I need to refresh the throttle position sensor when swapping a battery or response and mileage suffers until the system self corrects. Anything like that here, or is it just a spate of bad luck I'm having?

    -MKL
     
    #1 moshe_levy, Jan 21, 2012
  2. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,200
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Hi Moshe, that's a pretty big hit. Sometimes the displayed MPG is a little off after the "historical data" is reset (and it takes a while to rebuild that data). I'm not sure if that can account for your MPG hit, but try checking your MPG manually when you fill up.
     
    #2 uart, Jan 21, 2012
  3. cnschult

    cnschult Active Member

    Joined:
    Jan 9, 2008
    772
    95
    0
    Location:
    Michigan
    Vehicle:
    2005 Prius
    Model:
    N/A
    and do you know how to go into maintenance mode to check the voltage of the new battery? perhaps the new optima wasn't very charged when you received it, and in the winter you are running lots of accessories like radio, front and rear defrost, headlights, etc so if your trips are short the alternator may not have much time to recharge your new battery. but plz do check the voltage following procedures found on priuschat
     
    #3 cnschult, Jan 21, 2012
  4. cnschult

    cnschult Active Member

    Joined:
    Jan 9, 2008
    772
    95
    0
    Location:
    Michigan
    Vehicle:
    2005 Prius
    Model:
    N/A
    .:mad:
     
    #4 cnschult, Jan 21, 2012
  5. cnschult

    cnschult Active Member

    Joined:
    Jan 9, 2008
    772
    95
    0
    Location:
    Michigan
    Vehicle:
    2005 Prius
    Model:
    N/A
    :welcome:
     
    #5 cnschult, Jan 21, 2012
  6. cwerdna

    cwerdna Senior Member

    Joined:
    Sep 4, 2005
    12,544
    2,123
    1
    Location:
    SF Bay Area, CA
    Vehicle:
    2006 Prius
    Nope, about the only things that I can think of that need might need to be reset are power window initialization, radio presets and settings disabling the backup beep.

    http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html

    Dumb question... before when you got "40-41 range", were you resetting the MFD after each fill up? I don't know the MFD behavior that well since I ALWAYS reset it after each fill. For all I know, you might've been getting "27 mpg" for a long time and not realize it due to lack of reset. Disconnecting the battery reset it for you.
     
    #6 cwerdna, Jan 21, 2012
  7. moshe_levy

    moshe_levy Junior Member

    Joined:
    Aug 13, 2007
    62
    7
    0
    Location:
    NJ
    Vehicle:
    2008 Prius
    Model:
    N/A
    Yes, I always reset the MFD at each fill. And I fully charged my Optima myself before putting it in. I'm going to use this tank up and start fresh, and see what happens.

    -MKL
     
    #7 moshe_levy, Jan 21, 2012
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,699
    48,945
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    someone else got a bad optima and they sent him a new one.
     
    #8 bisco, Jan 21, 2012
  9. moshe_levy

    moshe_levy Junior Member

    Joined:
    Aug 13, 2007
    62
    7
    0
    Location:
    NJ
    Vehicle:
    2008 Prius
    Model:
    N/A
    I'm happy to report the problem self-corrected. Filled the tank again, reset the MFD, and logged another 250 miles today. 39.8MPG, which is fine considering it was all highway in under +28F, with 5 people inside and the AC on (for defrost). We're back on track!

    -MKL
     
    #9 moshe_levy, Jan 22, 2012
  10. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,200
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    The prius stores "historical data" on miles traveled and gallons added that it uses to improve the raw MPG calculations (that are based on the metered fuel injected).

    I had the same problem when I first got my Prius a few years ago. It had been reset by the dealer and it took a while before the reported fuel efficiency matched the actual (that I was getting from manual calculations).

    It might slowly improve even more over the next few tanks. That's what mine did.
     
    #10 uart, Jan 22, 2012
(You must log in or sign up to post here.)