1. Attachments are working again! Check out this thread for more details and to report any other bugs.

Regenerative Braking

Discussion in 'Gen 2 Prius Technical Discussion' started by SteveLee, Jan 16, 2013.

  1. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    I had thought that in the regenerative braking system that applying the brakes maybe caused some mechanism in or around the wheels to generate electricity. But is it less that braking is generating electricity and more that regerating electricity is resulting in braking or faster deceleration? I'm beginning to think "Regenerative Braking" is kind of a misnomer. Maybe "Regenerative Deceleration" is more accurate.

    I see now that all generated electricity for the system comes from the MG1 and MG2. Whenever pressure is removed from the accelerator the system starts generating electricity charging the HV battery. My question is, does the braking motion, pushing the brake peddle, have any effect on the charging system? How much, when, and how? Can you be accelerating and have a certain amount of pressure on the brake peddle that activates the MG's to generate power? I guess I need to find more detail on how and what each of the MG's do.
     
  2. nh7o

    nh7o Off grid since 1980

    Joined:
    Dec 10, 2011
    1,686
    337
    0
    Location:
    Hawaii
    Vehicle:
    2009 Prius
    Model:
    II
    Yes, the braking pedal modulates the amount of power that is regenerated by the MG. There are a few factors, such as state of HV battery charge or speed, that determine how the regen vs. friction ratio is changed. You are right in that the regen system can not brake the car to a complete stop. It is inactive below 8 mph.

    If you can run the Prii_dash software (forum is here on PC) you can see how the the friction braking vs. kW of regen power can vary. (Do it while someone else is driving.)
     
  3. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,338
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    Your Regenerative Deceleration is correct as well as the Regenerative Braking. If you take your foot off of the gas and decelerate the car will apply a small amount of regeneration to simulate engine drag of non-hybrid cars. As stated above the amount of pressure on the brake pedal will determine the magnitude of regenerative current used for deceleration or braking that is generated by MG2.
     
  4. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    So it sounds like you area saying there is a varying amount of power generated depending on the amount of pressure on the brake peddle? I thought I read someone, maybe from Patrick, that the level of charge, the amps produced, by the MG is a constant level. It is either charging or it's not. Maybe I'm confused.
     
  5. nh7o

    nh7o Off grid since 1980

    Joined:
    Dec 10, 2011
    1,686
    337
    0
    Location:
    Hawaii
    Vehicle:
    2009 Prius
    Model:
    II
    Yes. The level of current generated by MG2 varies. I've seen some peaks of 80A when pressing hard on the brake pedal, and it goes all the way down to zero at low speeds.
     
  6. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,338
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    +1 All you have to do is watch the HSI screen in the regen region to the far left and watch it vary as you apply brake pressure. Also watch it as you approach a stop. The regen from MG2 is rarely ever constant.
     
  7. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

    Joined:
    Jun 28, 2012
    775
    359
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2005 Prius
    Model:
    Three
    Think of it this way, when all is well, you are pushing against a brake pedal simulator. When you push the brake pedal it feels like a normal braking system to you. In reality, the car is watching what your foot is doing and deciding between and how much regenerative braking and/or thermal braking to apply. When a problem arises, the system turns into a conventional system without power assist, just like cars in the olden days.

    Avi
     
    JMD likes this.
  8. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    I don't think I understand. I haven't seen any regen display on the MFD. Is there a view I haven't seen yet on my 05? How do I get to it. I couldn't find anything about it for the Gen2.
     
  9. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    What are you using to see the amps output?
     
  10. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    I have felt different sensations in the braking process but didn't know exactly what they were. It's starting to make more sense now I think. Is there an article or white paper on this somewhere? I haven't been able to locate one yet.
     
  11. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

    Joined:
    Jun 28, 2012
    775
    359
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2005 Prius
    Model:
    Three
    Try this link.

    Avi
     
    SteveLee, seckwielen and JMD like this.
  12. nh7o

    nh7o Off grid since 1980

    Joined:
    Dec 10, 2011
    1,686
    337
    0
    Location:
    Hawaii
    Vehicle:
    2009 Prius
    Model:
    II
  13. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    17,039
    10,013
    90
    Location:
    Western Washington
    Vehicle:
    Other Hybrid
    Model:
    N/A
    But his 2005 doesn't have the HSI screen. That arrived with the 2010 model.
     
    jdcollins5 likes this.
  14. Britprius

    Britprius Senior Member

    Joined:
    Jun 14, 2010
    5,194
    1,910
    0
    Location:
    Herefordshire England
    Vehicle:
    2008 Prius
    No HSI screen on the gen2 only gen3, this could confuse the OP.
     
  15. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    5,131
    1,338
    0
    Location:
    Wilmington, NC
    Vehicle:
    2010 Prius
    Model:
    III
    Sorry, my mistake. The OP will need a ScanGaugeII or other device to see the regen current flow then.
     
  16. Britprius

    Britprius Senior Member

    Joined:
    Jun 14, 2010
    5,194
    1,910
    0
    Location:
    Herefordshire England
    Vehicle:
    2008 Prius
    I am sure we all make this sort of mistake when we move into another forum than our own vehicle, I know I have.

    John (Britprius)
     
    babybird likes this.
  17. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    Thanks. That helps me better understand the process.
     
  18. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
  19. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    No problem. I thought that may be the case but wasn't sure.
     
  20. SteveLee

    SteveLee Active Member

    Joined:
    Sep 15, 2012
    645
    179
    0
    Location:
    North Carolina
    Vehicle:
    2010 Prius
    Model:
    I
    So, there is a varying amount of electricity generated depending on the level of the peddle within the range of motion. Light peddle application allows a little power generation and further peddle application allows more power generation, also depending on other factors processed by the computer.? So it is possible to maintain speed with the accelerator peddle while generating power with the slightly depressed brake peddle? Not that I think that would be a good practice, just saying, for a better understanding of the capabilities.