Dr. Prius % State of Charge on Traction Battery

Discussion in 'Prime Main Forum (2017-2022)' started by pasta4breakfast, Jun 15, 2025 at 6:27 PM.

  1. pasta4breakfast

    pasta4breakfast Member

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    2020 Prius Prime
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    I recently got an OBD scanner and started playing around with the Dr. Prius app on my 2020 Prius Prime with about 99,000 miles. Almost 93,000 miles have been in EV mode. When I charge the car to 100% on the dash, the Dr. Prius app says the battery's actual state of charge is 87.42%. That seems a bit high. I think I remember posts that the top buffer is 15-16%. I wonder if the car is letting me access a little more of the battery as it degrades to prevent the range from dropping noticeably. Based on the amount of electricity purchased at chargepoint sessions, I estimated that my battery degradation has been about 10%, but maybe it has degraded quite a bit more.

    Has anyone tracked their top-end actual state of charge over the years? I wish I did this from the beginning to get a baseline.

    If relevant, my delta SOC has fluctuated between 0.5-3.5%, my volt diff has been almost always 0.01v, sometimes 0.0v. When the EV range is used up, the Dr Prius app says the state of charge is 13.33%.
     
    #1 pasta4breakfast, Jun 15, 2025 at 6:27 PM
  2. john1701a

    john1701a Prius Guru

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    I filmed this same drive, at as close to the same temperature and time of year each time, over the course of several years. Just walk backward through my channel to see that history... Here's the newest...

     
    #2 john1701a, Jun 16, 2025 at 2:41 PM
  3. jacktheripper

    jacktheripper Senior Member

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    Hi @pasta4breakfast ,

    A few factors can affect the final state of charge after charging — things like temperature, charging current, and how well-balanced the battery is.

    One trick we've found helpful for achieving a higher SOC is to set a timer on the charger to disconnect briefly in the middle of the night. You’ll often see a higher SOC by morning.

    Also, we're currently working on a higher-capacity lithium pack for the Prime — testing is expected to begin later this year.

    PS: Dr. Prius simply read the SOC from the ECU.

    Jack
     
    #3 jacktheripper, Jun 16, 2025 at 5:51 PM
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