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Possible Battery Problem?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Peppe, Nov 18, 2014.

  1. Peppe

    Peppe New Member

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    I'm taking my 07 T-Spirit to Toyota tomorrow but I'd love some advice first in case they try to fob me off! Luckily it's under warranty.

    I've noticed recently my mpg has dropped from an average of 60 to 50, I put this down to my driving (I bought it in July, at first I drove it v carefully, now I'm slightly less conscious of economy, but not massively so).

    Today I started my car and drove for 10 minutes in stop start traffic for less than a mile. I glanced at my consumption screen: the first 5 minutes was 15mpg, the next 5 minutes was about 10!! It was 10*C, I had my window demister on (which I switched from cool to hot air and back again).

    Driving around our small town (flat, slowish driving and stopping every 100-200 yards for roundabouts, no traffic) I kept an eye on the current mpg, it was flipping from one end of the scale to the other. I took a video, within about 40 seconds, the mpg goes: 20-35-9-2-4-15-50-20-40-80. I glance at the current MPG quite often and I have NEVER noticed it ever going down to 2mpg (or jumping around like that) even when powering up a hill, let alone plodding along a flat quiet road!

    Could this be the start of battery problems?? I was stuck in a big queue for ages in summer and noticed the MPG was about 20-30, for what it's worth.

    Thanks in advance
     
    #1 Peppe, Nov 18, 2014
  2. bisco

    bisco cookie crumbler

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    maybe, how many miles on her? welcome to priuschat!
     
    #2 bisco, Nov 18, 2014
  3. JC91006

    JC91006 Senior Member

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    not to worry, you have 11 years unlimited miles warranty. just drive and wait for a DTC to pop up......then worry
     
    #3 JC91006, Nov 18, 2014
  4. Peppe

    Peppe New Member

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    I think it's at about 45,000 miles? I've only got 1 year warranty on this model (which started in july when I bought it), so if it's going to go wrong I'd rather it's sooner rather than later!
     
    #4 Peppe, Nov 18, 2014
  5. vskid3

    vskid3 Active Member

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    Has the MPG dropped as the temperature has dropped? Stop and go traffic with a cold engine in the cold will get you poor mileage (for a Prius).
     
    #5 vskid3, Nov 18, 2014
    kenoarto likes this.
  6. Peppe

    Peppe New Member

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    I think the cold has had an effect yes, but nothing as extreme as today. The Toyota service centre did say that economy will drop in the cold weather but shouldn't be that low.
     
    #6 Peppe, Nov 18, 2014
  7. bisco

    bisco cookie crumbler

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    don't the dealers do free battery tests over there?
     
    #7 bisco, Nov 18, 2014
  8. vvillovv

    vvillovv Senior Member

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    Before I took the car into the dealer I'd take the car on the highway ( 100 kmh ) for an hour than see how your city mpg does the next day.
    If a short highway trip helps city mpg in the short term, I'd take it on the highway more often to see what effect it has.
     
    #8 vvillovv, Nov 18, 2014
  9. kenoarto

    kenoarto Senior Member

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    How old is the battery? If it's more than 4 or 5 years, you are living on limited, borrowed time.
     
    #9 kenoarto, Nov 18, 2014
  10. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    Accelerating, going up a hill, cold weather ... they all show very low mileage. Starting out in the recent cold and heating or defrosting you aren't going to get summer mileage. Cold weather drops tire pressure which drops mileage.

    Are you sure you didn't change the display mode so you are no longer showing average mileage but now instantaneous?

    Mine swings depending on what I'm doing. Even cruising on a highway up a slight grade can cause a 30-40 MPG swing.

    And the first few weeks I was very conscious of how I drove it, now not so much and that has effected MPG too.

    Use fuelly.com or hand calculate a couple of tanks to see how you are really doing.
     
    #10 mikefocke, Nov 18, 2014
  11. Jayw13702

    Jayw13702 Active Member

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    You mean the 12v battery?
     
    #11 Jayw13702, Nov 21, 2014
  12. Jayw13702

    Jayw13702 Active Member

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    I would say you are looking at the instant mph figure and not the average.

    My taxi displays the sort of readings you are talking about, especially when the traction battery is between 40-60% charged, if your 12v is starting to give issues then all of this is quite normal

    Mines a 05 t-spirit with 93,000 miles on and, the 12v has just been replaced and the difference is a noticeable one
     
    #12 Jayw13702, Nov 21, 2014
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  13. uart

    uart Senior Member

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    Probably the engine was idling because you were in hybrid stage 3a. The MPG will go very low if the engine is idling at low speed. After you've warmed it up you need to stop for 10 seconds and see if the engine cuts out. Then check the mpg figures again.
    http://www.techno-fandom.org/~hobbit/cars/five-stages.txt

    As for warranty over this? Let me just say that if there are no error codes, then realistically the probability of the dealers even diagnosing a problem in the first place is close to nothing, never mind warranty. Seriously this, if the experience of other users on these forums is anything to go by, the success rate of dealers diagnosing reported problems of reduced fuel economy in the absence of any error codes is pretty much 0% here.
     
    #13 uart, Nov 21, 2014
    Last edited: Nov 21, 2014
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