Battery fully charged (saturated) during a descent, but ICE stays on for long time after that

Discussion in 'Gen 4 Prius Technical Discussion' started by flic, Nov 13, 2017.

  1. Dxta

    Dxta Senior Member

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    Could you expatiate on the warm stages? You seem to insinuate there are stages to it.

    No offence meant here. Just wanna learn!
     
  2. flic

    flic Junior Member

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    I have monitored downhill in B with HA. I'm sorry to confirm that there is a small but not negligible fuel consumption.

    Inviato dal mio SM-N9005 utilizzando Tapatalk
     
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  3. RCO

    RCO Senior Member

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    I accept your pedantic discovery with good grace. Is there sufficient fuel used to mention a quantity, however negligible that may be?:)
     
  4. flic

    flic Junior Member

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    0.5 - 1.5 l/100km is low, but for sure it isn't a "no petrol burnt"

    Posted via the PriusChat mobile app.
     
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  5. RCO

    RCO Senior Member

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    Thank you.
     
  6. axle2152

    axle2152 Active Member

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    What does "HA" refer to?

    I wonder what the fuel rate per hr is when going downhill. If we didn't get 9" of snow I'd go out and test this but will have to wait for the weather to clear up.

    1-1.5 l/100km would indicate at a certain speed...so we would want to look at fuel consumption over a period of time. What I can say is that the fuel rate is definitely quite low. The fuel rate I have set up with the OBDII adapter only shows the first decimal place (0.0 US Gal/hr) but that's what I have showing up on the dashboard so hopefully I can get a few more decimal places when recording to a log.

    Definitely curious about this and I should (hopefully) have the ability to tell one way or another.
     
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  7. flic

    flic Junior Member

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    Hybrid Assistant App for Android and OBD2

    Inviato dal mio SM-N9005 utilizzando Tapatalk
     
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  8. wjtracy

    wjtracy Senior Member

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  9. laevus

    laevus Junior Member

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    The "moderately bad" effects of a saturation in a downhill.

    Engine starts spinning at 74% of SOC.
    After downhill, it tooks 6km and 7' to resume a (quite) normal behaviour.

    The HV Battery Temperature seems to be the major driver of the manner in which saturation develops.



    -----------------------------------------
    Notes on Gauges

    HSI.
    Numeric indicator of PowerMeter. Values:
    - 512 car in P, R o N
    - 0 car in D or B with no power fluxes to/from wheels.
    - [0 ÷ 50) First semi-zone of the ECO area in the PowerMeter.
    - [50 ÷ 100) Second semi-zone of the ECO area.
    - [100 ÷ <512) POWER area.
    - [1024 ÷ >512) RECHARGING area. Its should be intended as negative values, subtracting 1024 from them.

    CCL.
    Charging Current Limit. Maximum of current the battery can adsorb. Expressed in kW, negative values.

    Min V and Max V.
    Limits of voltage of the single battery blocks. To control that no misalignment of the series elements occurs. Ideally they should be equal.

    HV Battery Temp2.
    In the central zone of the battery. The more exposed to heat.

    Battery Fan and Frequence.
    Battery Fan indicator is set to 0 when the Fan is OFF.
    It's set to 1 (and more?) when Fan is ON.
    The Frequence is the speed (variable) of the Fan.

    Fuel System Monitor.
    My mistake. I was looking for a fuel rate indicator but I wasn't able to find a working one.


    -----------------------------------------
    Time line

    - 0' 00"
    Engine already warm (in S4 status).
    Fan activated during previous route. It started at 36° and, later, it will turn off at ~34°

    - 1' 05"
    Beginning of the downhill. SOC 49%, Battery temp 35°.

    - 4' 00"
    At SOC 69% and Battery 35°, CCL begins decreasing (in module) from the initial -32kW value

    - 4' 38"
    Beginning of "Saturation": ICE spins dragged to ensure motor brake and not turns off during electric traction at low power (HSI 0÷50).
    SOC is 74%. Battery temp is 36°. CCL, in rapid decrease, is 13kW, still allowing some recharging of battery.

    - 5' 03"
    Fully saturated. CCL is 0 and no recharge is allowed. Electric traction, controlled by DCL (not shown), continues functioning, with an unchanged limit (max ~20kW), but with ICE always spinning. Battery temp is 36°. SOC is 75% and, until CCL remains 0, can only diminish.

    - 7' 10"
    Continuous downhill finished. Next path has an up and down profile, with a certain prevalence of descents.
    SOC, at 72%, has lost few units. Battery temp is 37°. CCL is always 0 and the saturation persists.
    The car stops at an intersection. Engine temporally goes OFF, but resumes continuous spinning once moving .

    - 9' 00"
    CCL leaves 0 value and starts a slow augmenting (in module). SOC is ~66% and Battery Temp 36°. Engine continues spinning.

    - 11' 00"
    ICE continues spinning. SOC is 60%, Temp 36°, CCL reaches -5kW.

    - 12' 24"
    As soon as Temp reaches 35°, ICE stops spinning. SOC is 63% and CCL -5kW. But is an unstable status and after few seconds Saturation restarts.

    - 14' 05"
    ICE stops again. SOC is 59%, Temp 35° and CCL -5kW.
    Now Saturation appears to be definitely over and system resumes a normal behaviour, although still limited in recharging power (CCL).
     
    #29 laevus, Feb 5, 2018
    Last edited: Feb 5, 2018
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  10. Andyprius1

    Andyprius1 Senior Member

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    Very interesting and complete, TY
     
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  11. axle2152

    axle2152 Active Member

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    From my observations from the last couple of months, I would say temp is a factor, sure but it seems the bigger determination is how quick the charge and discharge occurs. Have had the battery on mine well over 38 C, upwards of 43 C in my case--we'll see what happens when summer gets here. If the charge up is from a simple coast which equates to a 20-30 amp charge, and the discharge is slow there's a good chance the WIN_CONTROL_POWER (labeled CCL in the video) will recover over 16kW before the battery is discharged...which is about the level where things seem normal with EV mode and whatnot, speed is also a factor when the WIN is under 16kW, you'll find that the car will go out of EV mode at a lower speed. If the the discharge after a long downhill charge is quick you'll probably get down to 2 bars of SOC and might notice that the car feels a bit sluggish, if you look at WOUT_CONTROL_POWER you'll find that it is down around 9-10 kW as opposed to the normal 21kW.

    Bottom line is that this behavior is normal. The ECU update from the TSB attempts to slow down the charging. When we start going down a long hill and you're riding the brake you're shoving in 100-130 amps into the battery. Seems that before after the ECU update (mine was affected) the car will now stop charging at the high current (120A) sooner and exit EV mode and slow the charge down to 20A until the WIN value goes down to 3kW and at that point there is no charge. While I can't confirm without recording data, it seems prior to the ECU update the battery would get charged a bit more, triggering a more aggressive discharge.

    All in all it seems all this is in effort to reduce heat generated by the battery, and reduce stress on the battery cells.

    Hopefully that all made some sense. Trying to sum it up without collecting a bunch of data and posting a bunch of charts.

    As far as temperatures go, drive in ECO mode instead of PWR.
     
    #31 axle2152, Mar 6, 2018
    Last edited: Mar 6, 2018
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  12. laevus

    laevus Junior Member

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    Which chemistry has your Prius? NiMh?

    Till now I have not found any reductions in discharging current. At least since I can measure it.

    I used the old acronyms, common in OBD APPs, Charging Current Limit (CCL) and Discharging Current Limit (DCL) instead of the names WIN_CONTROL_POWER and WOUT_CONTROL_POWER of the library Toyota Enhanced Diagnostic.
     
    #32 laevus, Mar 8, 2018
    Last edited: Mar 8, 2018
  13. jdenenberg

    jdenenberg EE Professor

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    His pofile says 2016 Prius 2 and in the US that model has NiMh. My 2016 Prius 3 has LiOn.

    JeffD
     
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  14. axle2152

    axle2152 Active Member

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    Yes, NiMH. The only conditions that there should be a limit on the discharge would be when the battery is too cold or due to low SOC.

    So what typically happens, I go down a long hill for several miles, the battery gets charged to the max (around 75-80) and stops accepting any more charge. Then as the road levels out the system will discharge the battery. Now depending on how I drive, terrain, the battery will discharge down to 35-40% (2 bars SOC), the WIN_CONTROL_POWER value sits at -3 kW, so battery won't charge or no more than 5 amps. Once the battery is discharged below 40% that's when the WOUT_CONTROL_POWER starts dropping from a normal value of 21 kW.

    So the conclusion is, depending on how quickly the battery drops when WIN_CONTROL_POWER is at -3kW, you may notice a drop in performance.

    I assume there more factors at play, temperature, power output. It is almost as it they're trying to control the number of "charge cycles" over a period of time. It seems that in stop and go traffic, if you pick up a lot of energy coming to a stop the WIN_CONTROL_POWER will start dropping. Very finicky and also quite interesting how the system manages itself over a wide array of driving styles and conditions.
     
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  15. lluchana48

    lluchana48 Junior Member

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    Muy interesante todo. Muchas gracias a todos
    Very interesting everything. Thank you very much to all
     
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  16. gstuart

    gstuart New Member

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    Has anyone had a situation where their prius runs the ICE (after going down a long hill) until the battery drops to 1 bar and there is not enough electrical power to move the car? Luckily after turning the car off for a while there was enough power to start the gas engine but it sounds like a bad fault to me. My toyota dealer says the hybrid system checks out fine but I can replicate this problem any time I drive in the mountains. I'd like to know if anyone else has encountered it or if it's just my car.
     
  17. bisco

    bisco cookie crumbler

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    are you saying you couldn't move in ev mode, or the engine wouldn't start and the car was dead in the water?

    if the latter, ask the service manager to ride with you so you can show him, there is something seriously wrong with your car.
     
  18. axle2152

    axle2152 Active Member

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    There is a TSB out you may want to check if your VIN is part of it. I had a 2016 Prius that had the issue -- everything would work itself out and drove fine unless I came to a stop. The fix is a ECU flash with new software and as long as you're under warranty it shouldn't cost you anything.

    TSB (NiMH only): Reduced power when accelerating from a stop | PriusChat
     
  19. axle2152

    axle2152 Active Member

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    To better expand on what's happening... In a nutshell, in the mountains there is a tendency where you can reach the maximum SOC (about 75-78 % SOC for the NiMH), well once it hits that ceiling it will "burn" through that charge and normally when the battery SOC "bottoms out" around 30 % SOC the battery should start taking a charge but without the ECU flash it doesn't...not for a while anyway. You should see only 1 bar of SOC on the display when you start really noticing the lack of power and if you stop the car won't want to go unless you floor it and mine it kind of jerked. The first time it happened to mine I came down Brasstown Bald (tallest mountain in Georgia) and thought I F'd up the trans-axle.

    Then I got curious and got a OBDII scanner and there are two data PIDs that you can watch that pretty much tell the tale:

    I hope I've remembered the names correctly but should be similar

    WIN_CONTROL_POWER (power input, measured in kW, 0-32 for the NiMH)
    WOUT_CONTROL_POWER (power output, measured in kW, 0-21 for the NiMH)

    You also would wan to look at the state of charge (SOC) of the battery, mine would dip down below 20%, after the fix I would seldom see it under 30% if I can recall correctly (the Prime is a different animal but does have the same data PID's...these cars are pretty cool).

    Here's a play by play, you come down a mountain and hit the maximum SOC (~75%), this causes the ICE to start might hear it rev a bit and even more so if you're having to use B. At this point the WIN_CONTROL_POWER drops to 0.0 kW, so no more charging. The road levels out but not enough to really use the ICE, the battery discharges down to 1 bar SOC around 20% SOC and the ICE begins to rev on level road, one bar remains. At this point the WIN_CONTROL_POWER still reads 0.0 kW or a very low value less than 3.0 kW and there isn't any significant charging, the WOUT_CONTROL_POWER is reduced to a low value restricting the battery's output to the wheels, this value from my memory would dip down to under 9.0 kW (normally 21 kW).

    Now these control values, it is normal, especially on a cold morning for them to start out low and same when the battery pack gets hot, the charge performance and output are reduced to prevent damage to the battery, slow down wear and tear, etc.

    The ECU flash prevents the SOC of the battery from getting so low so that there is enough of a reserve of power to prevent the problem. The flash effectively reduces the chance of the problem from happening.
     
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  20. A440SPS

    A440SPS Junior Member

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    On a long downhill, B mode does engine braking.

    But once full SoC is reached, isn't it better to switch to D and use the brakes lightly in regen mode, to avoid wear by spinning the ICE?

    --Cy--
     
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