Partial power reduction while accelerating onto highway

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by maleko, Oct 25, 2022.

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  1. maleko

    maleko Member

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    2008 Prius
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    Yesterday while getting on the highway, I stomped the pedal to the floor like I do every time and after a few seconds of strong acceleration my 2008 Prius faltered and lost most of its power output, struggling to hold 50i-60sh mph while merging onto the highway.
    No serious sounds / warning lights or anything errored out on the dash or otherwise. The only thing I noticed was my HV battery gauge was showing 1 bar on the touchscreen (MFD?) at the time of the incident, but I have never had an occurrence such as this before that I have noticed, regardless of the HV gauge's reading. (The A/C was also on medium at the time, and never lost its cooling or output during this event.) I have had previous incidents that threw the big red triangle and I lost all power and A/C cooling, etc. But again, this incident threw no errors.

    After backing off the throttle and cruising in the slow lane for a minute or few and letting the HV pack increase another bar on the dash, everything was back to normal and made it home no problem. Any ideas what to check? Should I be concerned?

    NOTES:
    My Pri has ~160k on the dash, but probably closer to 200k+ in reality (its dash rarely works these days and I don't believe it counts miles when the dash is off). I commute 90+ miles/day currently, service it well, top its oil off every other day, changed its transaxle oil when we first bought it around ~2014 (probably due again), etc. Have replaced the HV pack with a quality 2015 swapped pack from a PriusChat user approx ~2-3 years ago (not long before the pandemic iirc), spark plugs at least twice since owning it, and the coolant inverter pump most recently (also did the diverter valve previously as well). Still running the original 12V aux battery that came with it. Despite having a clean title, it is really two Pri's melded and skinned together but has been very reliable mechanically since owning it. I do have an ODBII cable with TechStream I can connect if need be.
     
    #1 maleko, Oct 25, 2022
  2. Tombukt2

    Tombukt2 Senior Member

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    It's more than likely the low battery in the air conditioning on no matter what happens at other times when you run the car down to that low you can expect these kinds of things to go on if they don't you're lucky and that's about it. They should be happening when you're at one bar and the air conditioner doesn't matter whether it's on lower medium that's the fan speed the compressors turning it's on that's also using quite a bit of power voltage etc and then your car is old with almost 200,000 miles on it although mine doesn't do this with close to 300,000 mi but I also don't beat the hell out of it trying to get on the highway with one bar in the air conditioner flying away generally speaking. And I have noticed since I put the brand new Toyota Panasonic battery rack in it's not done any of this I drove it around about a year with a faltering battery playing all the games and all the nonsense trying to just patch it through and all that to no avail The minute the battery was changed the HV battery was back to a new card it's been that way for about a year now. So I know that when things like this start going on with most of these cars we're starting to get into batteries that are starting to falter whether we like to admit that or not that's basically what's happening and as soon as that's corrected you're back to not posting on here again and driving a lot least that's what I noticed.
     
    #2 Tombukt2, Oct 25, 2022
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  3. maleko

    maleko Member

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    Just checked, @TMR-JWAP hooked me up with a 2015 ~30k miles salvaged and refreshed pack back in August 2019. My Pri mostly sat for 1-2 years with very light duty while I worked from home mostly during the pandemic. I think early this year is when we switched back to the office again and the 90 mi/day commutes started back up. Either way, no complaints. I know I run my car hard, but it has been a good car with minimal issues imo. I generally keep the MFD touchscreen display turned off and don't pay much attention to the battery gauge or otherwise since when the dash is off, I don't get fuel mileage metrics anyways. I will continue running it as usual and keep an eye on everything.
     
    #3 maleko, Oct 25, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    The battery bar graph on the dash is essentially a zoomed-in view of the range between 40% and 80% state of charge for the battery, which is where the car likes to keep it. If you have Techstream or another scan tool watching the actual state of charge, you'll see the car likes to keep it spot on 60% most of the time, it will go down from there when helping you accelerate or climb hills, and it will go up from there when being charged, or on downhills or decelerating.

    And you'll notice any time you are accelerating or hill climbing and the SoC drops below 40%, all the electric assistance you're getting immediately switches off, and it's suddenly just you, your 3,000+ pound car, and the 76 HP gasoline engine pulling it. And later on, once the state of charge is above 40% again, you'll have assistance again.

    It's just what the car normally does. Getting down to 40% might happen more easily, more often with an old tired battery, but even with a shiny new one, the same thing will happen any time it goes below 40%.
     
    #4 ChapmanF, Oct 25, 2022
  5. mr_guy_mann

    mr_guy_mann Senior Member

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    As stated, what you experienced is normal when the HV battery SOC is low. And having low SOC is "normal" if for instance you are driving in stop and go traffic (esp with A/C on).

    The car tries to maintain about 6 bars on the MFD when driving. When the car isn't really moving (& can't do much regenerative braking) then it will run the engine (at 1 bar) only enough to charge up to 2 bars. Ask for lots of motor assist right then and the car can only give a little bit before the SOC is too low.

    Posted via the PriusChat mobile app.
     
    #5 mr_guy_mann, Oct 25, 2022
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  6. edthefox5

    edthefox5 Senior Member

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    You don't seem to understand the lack of power implications of one battery bar.

    And demanding max power with one bar and then going WOT on the gas pedal all the time really beats the engine up. Your aware of how hard this is on the engine right?
     
    #6 edthefox5, Nov 9, 2022
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