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Do I have the oldest OEM 12V battery (261104W)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by uart, Jan 5, 2012.

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  1. uart

    uart Senior Member

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    Did your MPG drop gradually Optimus, or was it fairly abrupt as the battery died?

    My battery is definitely a little weak (12.1V/11.8V at Acc/IgOn), but so far doesn't seem to be causing any loss of MPG (currently getting about 55 MPG).
     
    #21 uart, Feb 5, 2012
  2. uart

    uart Senior Member

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    Thanks Hal. Almost sounds like the old soft drink bottle deposit.

    I always like to keep one old battery on hand in my garage, one that's still got some life in it. Came in handy for example when I took my Prius battery out, used an old one connected with jumpers so as to keep all my settings. Only problem with having one on the bench is forgetting to charge it every so often. Then they really do sulphate up and become useless.

    It's a bit of a drive to the recycling center, and a bit of a pain to transport batteries. So I usually wait until I've got a few before I take them out there. I think that last time I went I took about four, and they gave me about $16 (which was ok as I wasn't expecting anything). :)
     
    #22 uart, Feb 5, 2012
  3. romad

    romad 2004 Prīus Base Former Owner (Sold 13 May 22)

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    When I bought my new battery last month the dealer parts didn't charge for a core; just asked me to bring in the old battery.
     
    #23 romad, Feb 6, 2012
  4. Optimus

    Optimus Member

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    It wasn't immediately obvious that the 12v was going out. This started happening a few months ago, as we started going into winter (when we normally expect a MPG drop anyway). But this time the "swing" was more. The situation was clouded by the fact that I did not block the radiator right away (I normally would have done this in the fall), so I figured it might have been that. So when I DID finally block the radiator, the MPG still did not increase to where I expected it to be. This winter has also been very mild with hardly any snow, so I had not been motivated to block the radiator sooner.

    Anyway, once I finally checked Maintenance Mode on the touich screen, I saw my battery voltage was about 12.1 with no accessories on, and when I turned the headlights on, the voltage dropped to 9.1.

    For reference, there was no core charge with my www Advance Auto Parts order and no requirement to ship the old one back. So, I will just drop it off for free somewhere.
     
    #24 Optimus, Feb 6, 2012
  5. 2009Prius

    2009Prius A Wimpy DIYer

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    This is proof to me that to check the battery we need to give it enough load such as turning the headlights on. My not-so-strong battery measured mere 12.0 V in IG ACC mode but holds 11.4 V in IG ON mode with headlights on. So we see two batteries both measured ~ 12 V with no load but measured vary differently (11.4 vs. 9.1) with load (headlights on).
     
    #25 2009Prius, Feb 6, 2012
  6. uart

    uart Senior Member

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    Yep, but it looks like he didn't test it in Ig-On mode for comparison. I've heard that powering all the systems and ECU's in Ig-On mode draws over 10 amps from the 12V. So probably quite similar to running the headlights.

    UPDATE. Ok I just did a quick comparison of headlights versus Ig-On and yes there are very similar.

    - Accessory mode (no other loads) I read 12.1 volts in the service menu.

    - Accessory mode + headlight (normal beam) it hovered between 11.7V and 11.8 volts.

    - Ig-On (without lights or any other loads) it reads 11.8 volts.
     
    #26 uart, Feb 6, 2012
  7. nerfer

    nerfer A young senior member

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    I've gotten 6 or 7 years out of every battery I've owned, I think that 4-year thing is a hoax by battery manufacturers to buy more batteries. Just like oil change chains push the 3,000 mile oil change despite what your owner's manual says.

    That said, I should run the diagnostic on my battery, it's right at 6 years now, so I need to keep a closer eye on it.

    Gas prices are continuing their inexorable climb, I don't want to be without a Prius (or worse yet, damage this one) at some unexpected time.
     
    #27 nerfer, Feb 6, 2012
  8. kenoarto

    kenoarto Senior Member

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    Why not drive on bald tires too? They work until ...
     
    #28 kenoarto, Feb 6, 2012
  9. uart

    uart Senior Member

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    Hi Nerfer. I'd be really interested to know what voltages you're getting for comparison. If you know how to enter the service menu to test it then please post your results for no-load (fans lights off) in 1. Accessory mode and 2. Ig-On mode.

    BTW. Make sure to do the test after the car has been sitting for about 3+ hours to get the most realistic results.
     
    #29 uart, Feb 6, 2012
  10. 2009Prius

    2009Prius A Wimpy DIYer

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    Uh never occurred to me that the headlights could be turned on in ACC mode.
     
    #30 2009Prius, Feb 6, 2012
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