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How to understand the battery meter.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Dad of 4, Sep 12, 2013.

  1. Dad of 4

    Dad of 4 New Member

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    I just purchased a 2008 Prius with 96000 miles on it. It has a 30 day 1000 mile warranty from the dealership so i have been hypersensitive to anything as I don't want something that should have been fixed to slip away. My major concern has to do with the batteries. I have no idea what to look for. The battery meter on the display shows a fluctuation from 2 bars to 7 bars on my 10 mile commute to work. It that normal? Also, today as i was in a restaurant drive through the battery was at 50% and then i looked up and saw it down to 1 bar then in a couple of minutes I was back over 50%. Do others see this, or is mine abnormal? Also, how much checking on battery condition can I do on my own? (This is my first Prius). I would love to be more confident in my purchase. Thanks for any advice that you may have.
     
    #1 Dad of 4, Sep 12, 2013
  2. uart

    uart Senior Member

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    It's more or less normal. Having less fluctuation is better, but there are definitely circumstances where you do get that degree of fluctuation. For example, if the weather is hot and the aircond is on full blast then the SOC (state of charge) can drop quite quickly once the engine is off (like in the drive-thru).

    If you want to minimize your SOC fluctuations then try allowing the engine to warm for about 40 seconds (transmission in "P") before driving off in cold start situations. Also, if possible, you could try a somewhat higher temperature setting on the aircond when in stop start situations.

    Yes there's quite a lot of self testing possible. You can now get OBD port devices to monitor the battery's health.
     
    #2 uart, Sep 12, 2013
  3. Dad of 4

    Dad of 4 New Member

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    Thanks for the help. I am new to the entire Prius experience and am a little jumpy as I don't think I will be able to work on these like I have my other cars.
     
    #3 Dad of 4, Sep 13, 2013
  4. nh7o

    nh7o Off grid since 1980

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    If you want to look at the battery health, you can get the Torque app for Android, and a bluetooth OBDII interface. If you have a windows laptop, you can get the SXLink OBDII interface and run Prii-dash ( info here Prius OBDII Third-Party Apps | PriusChat ). Also the mini VCI on eBay. They can tell you how the various cell voltages are doing, what the internal resistances are, how much they diverge, and what sort of temperature fluctuations you are seeing.

    If you see battery temperatures over 50C, I would say there is something not right. Maybe the battery cooling fan is dirty, or maybe the battery internal resistance is starting to climb. Prius batteries seem to regularly last over 150K miles, but there are significant outliers that go much more and much less.

    If you can, do some continuous, non stop-and-go drive that is more or less level. The battery should eventually get to 5-6 blue bars and stay there without much change. You should be seeing somewhere close to 50mpg at moderate speeds on level terrain.
     
    #4 nh7o, Sep 13, 2013
    uart likes this.
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