New HV Battery Question

Discussion in 'Gen 3 Prius Main Forum' started by ALS, Sep 7, 2018.

  1. ALS

    ALS Active Member

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    Got a new HV pack in my car today and was wondering how long it takes for the computer to reset and adapt to the new pack. Gas mileage isn't that great in the first day. It is climbing, but not as quickly as it use to.

    I know it takes a little while but what am I looking at time was before things get back to normal.
     
  2. Raytheeagle

    Raytheeagle Senior Member

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    How many miles have you put on the car since the new battery install?

    What mpg are you at and where were you at before?

    How many miles on your Prius?
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Personally, I understand the thought behind this, but have yet to experience it.

    In theory....if the 12v is disconnected during car maintenance, many "tweaks and adjustments" made by the ecus are reset to default and this can cause running issues when there are components (like a throttle body) that have wear/tear/carbon buildup/etc. I've even heard of times the car won't start due to the throttle body having enough buildup that the throttle plate is not in the correct position for the default values.

    In reality, I haven't yet experienced this issue following an HV battery replacement, even though I disconnect the 12v battery every time I swap one. After building a battery and installing it in my car, I always take it for a test ride to my work parking lot 23 miles away (46 miles round trip) staying within 5 mph of all speed limits. My experience has been instant 48-53 mpg.

    If you're having significant issues with mileage, maybe disconnect the 12v for a minute and then take it for a 40-50 minute drive of backroad (40mph) and highway (65 mph) and see how it does after that.
     
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  4. ALS

    ALS Active Member

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    78K miles. New 12V about three months old. Low thirties before battery went to limp home mode and I got the dead battery walking code.
    Still in the low thirties and I put on about twenty five to thirty miles so far.
     
  5. Raytheeagle

    Raytheeagle Senior Member

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    Did toyota help you with the battery replacement?

    I’d run a tank or 2 before making an assessment of the replacement.
     
  6. ALS

    ALS Active Member

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    Yep Toyota gave me $750 and I got the dealer to discount the battery a few hundred. $2285 with labor and tax for a brand new Toyota battery. Not happy that I had to put a new battery in but it could have been much worse like $3,500

    That was what I was thinking that it's going to take the computer a few hundred miles to calibrate itself to my driving style.

    Already seeing a really big difference in the behavior of the car. There was this bump that felt like a normal transmission kicking into gear when I would accelerate from a stop. That has disappeared completely with the CVT transmission is running smooth now.
     
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  7. Raytheeagle

    Raytheeagle Senior Member

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    Having a new battery you will notice a difference.

    I recondition our 2010’s battery and prior to doing that, you could tell it was getting tired at 150k miles. Since reconditioning, it’s running well.

    We have a 2017 RX450h so I have a nearly new hv battery to compare behavior against.

    As you put more miles on, keep us posted on the differences(y).
     
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  8. ALS

    ALS Active Member

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    Low tire pressure light came on this morning so add to the fact that the dealer lowered all my tire pressures by 8-9 psi. That problem was corrected pretty quickly.
     
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  9. Grit

    Grit Senior Member

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    What was the solution to that? Interested because it was resolved “pretty quickly.”
     
  10. JC91006

    JC91006 Senior Member

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    I would check for a nail in your tire
     
  11. ALS

    ALS Active Member

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    Free air pump at the local quarter car wash. Pressures are back up to 42F 40R.
    That's better than the 32-33 psi the dealer set them at.
     
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  12. Grit

    Grit Senior Member

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    I was expecting something pretty quick, I had a different idea.
     
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  13. ALS

    ALS Active Member

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    Just filled up with my second tank of gas since replacing the traction battery earlier this month. Wasn't impressed with the fuel mileage I got on that first tank 36.13 mpg. Two days into this second tank of gas it's a whole new story. The HSI is showing over 45 mpg and my Scan Gauge is running over 50 mpg on most of the errands I'm running during the day.

    So right now mpg's are improving as I drive the car. I'll let you know what this second tank gives me in a few weeks.
     
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