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Downhill Regeneration Battery test!

Discussion in 'Gen 3 Prius Main Forum' started by thordehr, Sep 1, 2013.

  1. thordehr

    thordehr Member

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    (SEQUEL TO MY DRIVE TO WORK BATTERY TEST)

    Traction Battery Monitor results and information interpreted. | PriusChat


    On the way back from work today I took the route that took me up Laurel Canyon and then back down to get home.
    At the top of Laurel, I shut the car down, put in the logger, started it back up, turned off the AC and rode the regenerative braking down the hill. I attempted to keep the charge portion of the dash graph going as much as I could without topping it out all the way and applying the friction brakes.

    I started out two bars from full, made it to full battery charge indicated and continued to regen for at least 1 minute past that point.

    At the end of this hill I got stopped at two lights and did two brief power mode full throttle accelerations up to about 45MPH to see what those would look like, the second one being bigger and longer. About 1/2 mile after that I was home.

    Here we go.

    The state of charge started at about 62% and then went up to a maximum of 80%.
    It never ventured above 80% even though I was regenerating past the time I got full bars on the dash indicator. I don't know if 80% is where the controller regulated itself to stop the charging. It's possible that the information bus can't send values past 80% or the logger can't interpret those values. Although, I did read somewhere that these batteries aren't allowed to get to either full or empty charge. I'm surprised to see such a sharp cutoff though...
    You can see the two places where the charge gets drawn down from the acceleration hits.

    [​IMG]




    Here's the High Voltage Amps.
    A few amps to get moving down the hill then negative amps (amps flowing towards the battery). What looks like three big spikes is showing the two big accelerations. The fact that the amps drop to negative briefly in the second stronger acceleration is probably something to do with the ICE kicking in and the MG1 briefly turning backwards as it pass through a particular MG2/wheel RPM. OR, it might just be a glitch in a data point.

    [​IMG]




    The HV battery pack voltage shows it peaking out during the regeneration, then dropping sharply while drawing amps for the two accelerations.

    [​IMG]




    MG1 and Inverter 1 temps as usual don't show a lot of useful information as it isn't directly related to wheel speed and can run forwards and backwards in different conditions even at the same road speed depending on what the ICE is doing.

    [​IMG]




    MG2 and Inverter 2 show pretty stable temperatures during the regen period then the motor temp jumps up in two steps for the two accelerations. The Inverter temps spike up then are drawn back down by the coolant before the second bigger hit.

    [​IMG]




    The battery inlet temp was starting to rise as the cabin temp increased with the AC off.
    Battery temps kept going up as they were being recharged. My previous max battery temp on the way to work was 39C. This time it hit 39C at about the time of the first two hits. It went as high as 43C after the hits.
    Leave a battery alone, the temp will be stable. Charge it, the temp will climb, discharge it, the temp will also climb.

    [​IMG]

    Guess I've played with this logger as much as I can now. Now what remains is to maybe every 6 months check the battery condition.
     
    #1 thordehr, Sep 1, 2013
    JMD likes this.
  2. jdcollins5

    jdcollins5 Senior Member

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    Good info on the downhill regen test.

    The Traction Battery Monitor really gathers some very useful data. I did much like you and have trended several commutes to work in both cool and hot weather.

    The most useful part to me is that now we have baseline data of the HV battery when it is healthy. As the battery ages we should be able to see minor changes beginning and before the battery gets in bad shape.

    Another good point to me is that you plug it in the OBDII port and forget it. No distractions from laptops, cell phones, etc.
     
    #2 jdcollins5, Sep 1, 2013
  3. macman408

    macman408 Electron Guidance Counselor

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    Yes, 80% is the max SOC, and is usually a very sharp cutoff. It may stop (or at least slow greatly) at about 78-79% if you've already hit 80% once during the day, and so the battery is already fairly warm. Once it stops charging, you're no longer getting any regen (beyond the small amount being used by the car's systems); it's completely friction braking and engine braking. (Shifting to B mode while this is happening will increase the engine braking used, decreasing the amount of friction braking necessary. Shifting to B mode before the battery is full will use a smaller amount of engine braking, and also increase the rate of regen when not pressing either pedal.)
     
    #3 macman408, Sep 2, 2013
  4. GasperG

    GasperG Senior Member

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    I have been driving on some serious hills (1.600 feet elevation in 6 miles) and when I monitor the battery temps it can rise up to 50° C, I checked if the cooling fan was working and it was working, although very silently. Always using B mode, luckily this is not my daily commute, but it's still several times a year.

    Should I be worried?
     
    #4 GasperG, Sep 2, 2013
  5. thordehr

    thordehr Member

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    #5 thordehr, Sep 2, 2013
  6. Michael Cline

    Michael Cline Junior Member

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    I did a bit of personal research into the differences between the standard 2010 Prius and the 2013 Plug in Prius (PIP). My 2010 Prius generates about 82 amps under full regenerative braking. I find this just enough to get stopped if I adjust my driving style to maximize my economy (which is about 60-65MPG commute, 55-60 MPG highway). On the 2013 PIP, the regenerative braking feels much stronger, and in fact generated around 142 amps in full regenerative breaking. It was a friends car so the test was limited to short hills and manufactured situations. This increased breaking power felt much more comfortable and closer to "normal" driving and I think is a key benefit of the 2013 PIP, and possibly other models as well. (Your chance to post your data on other Prius models!)
     
    #6 Michael Cline, Sep 10, 2013
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