Does the Prius have automatic cell balancing features?

Discussion in 'Generation 1 Prius Discussion' started by MArcin91t, Jul 3, 2026 at 4:50 PM.

  1. MArcin91t

    MArcin91t New Member

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    Recently, I've noticed that occasionally my Prius stops turning off the combustion engine and instead constantly charges the battery at a low current of around 5-8A (according to the Dr. Prius app), even though the LCD shows a full charge (and the Dr. Prius app shows 95% battery charge). I once had to drive about 35 km (18.5 mi), and after such a trip, the battery heated up to 52°C (125°F), even though the ambient temperature was around 15°C (59°F). Turning it off and on again disables this strange mode. I always thought the Prius didn't have a cell balancing function. Unless, of course, it's something else.

    Anticipating your question about battery health: Yes, my battery isn't in the best condition (delta V around 32%).
     
    #1 MArcin91t, Jul 3, 2026 at 4:50 PM
  2. ChapmanF

    ChapmanF Senior Member

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    Yes, that's totally a thing the gen 1 will sometimes do.

    My car did that HV battery rebalance thing again | PriusChat

    I may have freaked out the first time and interrupted it by turning the car off, but I later decided letting it complete what it's programmed to do was probably the better policy.
     
    #2 ChapmanF, Jul 3, 2026 at 6:17 PM
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  3. MArcin91t

    MArcin91t New Member

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    Interesting. I didn't think Priuses actually had something like that. I read that yours only happened once a year. Mine happens about once a month, but due to short driving distances, I haven't had a chance to finish it.

    Anyway, I started reconditioning the battery yesterday, so I think it won't start for a while.:D

    IMG_20260703_200601.jpg
     
    #3 MArcin91t, Jul 4, 2026 at 1:56 AM
  4. ChapmanF

    ChapmanF Senior Member

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    Well, as it doesn't exactly flash lights and ring bells when it happens, it's probably more accurate to say I happened to notice it on the order of once a year.

    Also, your gen 1 is by now nearly twice as old as mine was then.

    You can see in the post I linked it happened once on my way home from work, and as it was a nice day with no one expecting me at a particular time, I just altered plans and made a nice detour through the countryside to watch the process complete.
     
    #4 ChapmanF, Jul 4, 2026 at 9:28 AM
    Last edited: Jul 4, 2026 at 9:39 AM
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