Refreshed the HV Battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by SnT08Prius, Sep 19, 2021.

  1. SnT08Prius

    SnT08Prius Active Member

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    The Prius has been struggling up the Montana mountains for a little while slowing to about 50mph on the long climbs. In Arizona we could hold about 60mph.

    We also noticed that on the highway we would only see about 4 bars regularly and zoom up to green on the downhill runs only to run down again within a mile or so.

    I suspected that a few modules might be getting tired after 367,500 miles. I tried to get torque pro to work with the PID's but the ELM327 might be junk and not letting the HV battery data flow. (sadness)

    So purchased 5 cells for $140 and watched a whole bunch of battery vids on how to do the job. Run the battery down to 2 bars and took the battery out. The battery is a heavy bugger for sure!

    The key and safety plug were placed inside the house. :)

    Test volts:
    2 @ 7.59
    3 @7.58
    6 @ 7.57
    10 @ 7.56
    2 @ 7.55
    4 @ 7.54
    1 @ 7.52

    So I replaced # 3, 15, 16, 17 & 25 with units that had 7.62-7.64.

    Put it back in the car and I had 6 bars already! put the ac on and sat for a minute and watched the 4 blue bars vanish 1 by 1. OK time for a drive around the parking lot and as soon as I hit revers the red triangle of death lights up.

    PANIC sets in - and now only 1 bar left. (think swear words)

    Note to self - make sure your door is closed before driving off!
    Heart rate returns to normal and I get back to 2 bars, so I head our around the block and up to 3 bars in no time. Seems to be charging properly.

    Next is a trip to buy a 6mm tap (to fix something else on the new engine mount) and we are up to 4 bars by the end of the street - things looking good here. As we drive about 3 miles we hit 6 bars! happiness.

    So we head out to the freeway for an 80mph test and the car has more power for sure and only dropped to 4 bars under hard acceleration.

    Today we will do a 300 mile test with 3 large mountain climbs to see if we are back to holding 60mph!
     
  2. SnT08Prius

    SnT08Prius Active Member

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    So the trip netted mixed results. We had an extra 10mph on the climbs and did not drop into the purple at all holding a steady 60mph.

    However the the battery went green faster on the way down and then burnt off bask to 2 bars within a mile or 2! Not sure why that is or if it has to do with rebalancing itself.

    On the way back we managed 49.0mpg on 188 miles with 3 major climbs that took the battery down to 3 bars and held, We had a stable 4 to 5 bars on the flat and smaller rolling hills on Montana.

    One thing it did not like at all was the on ramp at Butte going from green 8 bars to 1 purple pushing up to 80 mph freeway speed to meld with traffic. It took several miles to get back to 3 bars.

    So my only real concern is the really fast drop from full to 2 bars and back - but this may be part of the re balancing or under load I still have some cells that are weak and will need replacing.

    Next step - get an ob2 reader that is capable of reading 2 ecu's
     
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  3. TheLastMojojomo

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    When going up mountain passes, you should try using cruise control if you haven't.

    Cruise control has much better HV Battery management compared to using your foot.

    I'd be interested to hear your results from cruise control doing other mountain passes to see if it conserves the HV Battery effeciently.

    Posted via the PriusChat mobile app.
     
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  4. Another

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    Try Cruise Control uphill and B Mode downhill?
     
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  5. TheLastMojojomo

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    Cruise control uphill for sure as I stated before it has better HV Battery management.

    Didnt mention B Mode at all but I wouldn't bother with it downhill.

    The Prius automatically goes into B Mode when the HV Battery gets topped off from regenerative braking.

    B mode engages max regen braking, but actually shunts the energy away from the HV Battery into spinning MG1 and the engine instead.

    This is why it engages when the HV Battery is full.



    Posted via the PriusChat mobile app.
     
  6. SFO

    SFO Senior Member

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    Best to grid charge/discharge the HV battery at this point.

    How much oil is being consumed between changes, and is the catalytic converter still OEM at 367.5k?
     
  7. fuzzy1

    fuzzy1 Senior Member

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    Your 'automatic B mode' is not the same as gear-shift-stick B mode. At least it isn't in my Gen3, and I'm not recalling it being materially different on this than Gen2.

    Your automatic-B is just a version of D-mode synthetic drag, normally slowly charging the battery, then shunting into low RPM engine braking after the battery is full.

    Shift-stick B mode is much stronger, initially using both battery charging (higher rate than auto-B) and engine braking simultaneously. When the battery fills, then all is shunted into the engine, greatly boosting RPM, possibly to full screaming banshee levels.

    On one particular hill were I compared the two modes after the battery filled, I was getting maybe 2000-2200 RPM in the 'auto-B' that you describe, vs 4600 RPM in 'real-B' mode. The former did not produce enough braking effect to hold the car's speed steady, so it was gradually accelerating up to unsafe speeds. The later was strong enough to hold downhill speed steady.

    On certain steep long descents that we have here out West, 'bothering with it' by selecting the shifter B mode is important to protect the friction brakes from overheating. If you can get by on just the automatic version, then your hills are not as steep and long.
     
  8. TheLastMojojomo

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    You're right actually.

    Very rarely do I have steep descents long enough to even fully charge the HV Battery and it's been a few years since I've had one.

    I guess the automatic B-Mode from being in D is just from the normal amount of regenerative braking that occurs when you let your foot off the gas.

    However, I wonder if when in "Automatic B-Mode", regenerative braking still occurs/scales when pressing the brake pedal. But it then shunts the excess energy to MG1 instead so the engine will rev high and cause a greater slowing effect from greater regen braking like in regular B-Mode.

    This seems to vaguely be my memory of how it worked a few years ago but could be completely wrong.

    Do you know if this is what happens? Or do the friction brakes just engage more with pedal input instead of applying regenerative brake at this point?

    I'll have to test this next time I'm on a long steep descent.

    I guess if this isn't the case what I would do on steep descents is wait until the HV Battery gets topped off in D from regenerative braking then switch to B-Mode.

    Posted via the PriusChat mobile app.
     
  9. Another

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  10. fuzzy1

    fuzzy1 Senior Member

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    I can agree with that description.
    In this situation, when the battery isn't full, I still see regenerative battery charging happening. But when the battery is full, it switches over to just friction braking, not engine braking. And both regenerative battery charging and friction braking may happen at the same time, depending on braking level and battery status.

    The car is quite flexible and forgiving, so it doesn't matter much which you do. My own preference, to first maximize energy recovery but then minimize both high-current battery heating and high-RPM engine whining time, is to enter B mode as early as possible without preventing the battery from filling up. This means:
    (*) long hills that will fill the battery regardless: use B from the top;
    (*) short hills that won't fill the battery with regenerative braking: don't use B at all;
    (*) intermediate hills: start with D and regenerative braking, switch to B part way down based on your best judgement or experience with that hill. The goal is to have the battery filled by the bottom.

    I will differ with this item on a couple points:
    Remember that B-mode braking is just front wheel braking, which is less directionally stable and more likely to slip out of control than 4 wheel braking. While regenerative braking is the same, at least from the pedal you are immediately primed to switch to the superior 4 wheel braking. There is no reason for foot braking to be "abrupt", other than lack of driver practice in winter conditions.

    First, one should have held speed down to legal and comfortable cruising levels before the B opportunity even arose. Second, it is quite unnecessary to slow down first before switching (excepting the icy conditions described earlier). The car has no upper speed limit for B mode, you can switch at any time without hurting anything (winter traction conditions permitting).
     
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  11. SnT08Prius

    SnT08Prius Active Member

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  12. SnT08Prius

    SnT08Prius Active Member

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    The battery has been stable all week around town holding 5 to 6 bars and getting 47mpg. That is a great improvement for sure.
    Tomorrow's test will be Yellowstone to Cooke city and a few very large mountains. They close the roads for winter in a few weeks.
     
  13. TheLastMojojomo

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    Try using cruise control and see if you notice a difference in HV Battery behavior.

    Posted via the PriusChat mobile app.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    Not all the way to Beartooth Pass? Though that might not allow enough wolf-watching time in Lamar Valley.

    My time in and around Yellowstone, with very high elevation (reduced drag from thinner air) and relatively low speed limits, produced stellar MPG in a pre-hybrid.
     
    #14 fuzzy1, Sep 25, 2021
    Last edited: Sep 25, 2021
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  15. Another

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    Great drive
    https://attachments.priuschat.com/attachment-files/2016/09/112875_CrossCountryPriusRoadtripAugust2016Pics.pdf
    Day 16
    Enter Yellowstone National Park, WY, from its West Entrance. Drive counterclockwise around the Yellowstone National Park loop RD. Encounter a bison walking right down the double yellow line of the loop RD twice during the day. Taking one handed pictures of a bison that you could reach out and touch through the driver's window is a trip. Hike the short trail through the Lower Geyer Basin with Fountain Paint Pots. Killed time waiting for the Old Faithful Geyser to erupt by hiking the trails around Geyser Hill and the Firehole River. Drive by Yellowstone Lake. Witness a wolf approaching an injured bison in a meadow in Hayden Valley. View the Upper and Lower Yellowstone Falls and Yellowstone Canyon by hiking the South Rim Trail from Uncle Tom's Point to Artist's Point. Notice signs on the South Rim Trail stating a bear has been seen multiple times in the area and that carrying Bear Repellant spray and knowing how to use it was advisable. Bear spray was available for rental at all Visitor Center Stores. Drive to Mammoth Hot Springs and hike the Upper and Lower Terrace Areas. Drive to Roosevelt Lodge to take pictures of trail rides and horse drawn coaches based at the Roosevelt Ranch. Exiting Yellowstone National Park through the Lemar Valley and Yellowstone's Northwest Entrance was a mistake. This exit path took me over the 10947 FT high Beartooth Pass on the switchback Beartooth Scenic Highway in a 34 degree wet snowstorm. Snow stuck to the grass, but thankfully, not the road. I should have exited through Yellowstone's East Entrance towards Cody, WY. Overnight in Cabala's parking lot in Billings, MT
     
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  16. fuzzy1

    fuzzy1 Senior Member

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    "Cross-country Prius Road Trip August 2016
    22 Days - 8895 Miles"

    :eek: That just isn't anywhere near enough days to do justice for such a tour! You spend too much time per day sitting in the car, rather than hiking outside, and miss too much! Our own cross-country Prius road trip, Sept-Oct 2015, took 44 days to cover 8000 miles. And we'd have done it again last year, to pick up even more stuff that we missed, if not for the Pandemic.
    I must generally disagree that this exit route was a mistake, unless it was all so foggy that you couldn't see anything. With decent visibility, Beartooth Pass is the right choice.
     
  17. SnT08Prius

    SnT08Prius Active Member

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    Finally got the torque pro to see my HV battery.... about bloody time I might say! So early readings show within .02 v between the cells - but that was only a few miles.

    Need a long test drive to get real numbers.
     
  18. fuzzy1

    fuzzy1 Senior Member

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    I ran that same hill again Monday, in different weather and load conditions than that previous gauging run a couple years ago. This time, after the battery filled, real B-mode produced 4800-4900 RPM and held the car down to about 60 mph, while switching back to D to get 'auto-B' caused the engine to drop to 2500-2600 RPM while the car slowly increased speed to mid-upper 60s. At that point I returned to real B and applied a small bit of friction braking to get back to just 60.
     
    #18 fuzzy1, Sep 29, 2021
    Last edited: Sep 30, 2021
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  19. SnT08Prius

    SnT08Prius Active Member

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    So after using torque pro for a 200 mile trip i noticed several things. 1. once it hit's 80% charged the B more kicks in automatically. 2, most of my battery cells are within a point or two most of the time with the fast updates tricking me. 3. the battery performed much better this trip than the last only dipping down to 2 bars for a moment and quickly gained back the charge to 4 bars.

    The range was 20.2 to 13.0 for most of the modules.
    The HV charge has me puzzled a bit as it swung between 64 to 14. it only built up when green going down hill and then vanished very quickly while producing 99.99mpg at highway speed.

    Iss this some sort of extra storage capacity that normally sits at 14?
     
  20. SnT08Prius

    SnT08Prius Active Member

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