I Just had my first annoying "excess battery power burn off" issue.

Discussion in 'Gen 2 Prius Main Forum' started by uart, Oct 7, 2009.

  1. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Ok I’ve read about this happening but it’s the first time I've ever seen it.

    Today I had a bit of start stop driving with traffic lights and it drove my SOC up to green (but still one bar from the top). This however all happened on a plateau just before a long slow hill decent (in traffic). As expected by the time I was nearing the bottom of the hill the SOC had all the green bars up and I hadn't yet even started to brake for the traffic lights that are right at the very bottom of the hill.

    Naturally I got caught by the red light at the bottom and had to pull up from about 70 kph and to me it still felt like it was doing mostly regenerative braking despite the full SOC.

    So then I'm stopped at the lights with my foot firmly on the brake and the SOC at 100% and the MFD started showing energy coming from the battery (kind of in pulses every few seconds) just the way it would look if you were driving on all electric, but fully stopped with my foot firmly on the brake it normally wouldn’t do that.

    Then after about 10 seconds it started up the ICE, all while stopped and foot firmly on brake, and continued to pulse power from the battery despite the fact I was going nowhere. Anyway I figured that this is the notorious nonsense that the computer does when it’s got too much battery charge and it doesn’t know what to do with it. Does that sound about right?
     
  2. Zythryn

    Zythryn Senior Member

    Joined:
    Apr 28, 2008
    4,960
    2,977
    1
    Location:
    Minnesota
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    Honestly I have never noticed that.
    Not saying it has never happened, just that I have never noticed it. I THINK I would have as I keep a pretty close eye on it, but who knows.
    Anyone else?
    I am curious now and will try to recreate the effect.
    How far down does it drain until you stop getting that type of behavior?
    Did it stop when you started driving?
    Were you running the AC/Heat or other draws?
     
  3. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    No there was no AC or other accessories running at the time. After it had finished "draining" the battery it actually still had all the green bars up, but as soon as I pulled way from the green light (ICE still running) it dropped back to one bar below full, so my best guess is that it drained just about all of the top bar.

    The really annoying part was that after those traffic lights my journey was all slow speed on nice flat road for about 1.5km to my final destination. So it could have pretty much gone electric all the way on that charge making full use of it, and I think it probably would have done exactly that I've I hadn't have been caught by the traffic lights.
     
  4. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    I have heard of this rather odd behavior, but never happened to me. I had topped the battery many times when driving in the mountains, but the car just ceased to regen and went to friction braking, as expected - I could perceive the change quite obviously. At that point, I switched to the "B" mode. The car never did anything odd or unexpected, it behaved just normally - I never experienced anything from what you describe. Maybe I have newer firmware revision which fixes this kind of behavior? do not know.
     
  5. Sandy

    Sandy Hippi Chick

    Joined:
    Apr 28, 2009
    860
    53
    0
    Location:
    Ocala,Fl
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Never happened to me....
     
  6. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    How about the EV switch? Do you have it installed?

    Well, my car would just go on the battery by itself until it dropped to the blues again whenever I topped it. It would not start the ICE unless I step on it rather harshly or went faster than warp speed. Just as you would expect, so I never had to use the EV button to discourage it from starting the ICE. But in your case, it might help.
     
  7. Politburo

    Politburo Active Member

    Joined:
    Feb 15, 2009
    971
    207
    0
    Vehicle:
    2009 Prius
    Sounds normal to me. I'm not sure what is so annoying or nonsensical about it, though. I'd rather have it spin the engine than damage the battery.
     
  8. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Yep I reached straight for the EV switch as soon as it happened and it just laughed at me and said "EV mode is currently invalid" on the MFD.

    And so would mine normally, but how do you propose that it could do that while stopped at traffic lights! You see I'm pretty sure that the stopping part had something to do with it.
     
  9. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Yes I know exactly what you're saying. To tell the truth I was really thinking the same thing at the time. I mean how was it to know that I hadn't stopped half way down the hill and was just about to make another big decent. It really did the safe thing.

    I was just a little peeved becasue I had all flat driving after those traffic lights. :)
     
  10. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    Sorry, I don't get your point - how does spinning the engine protect fully charged battery?
     
  11. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    Actually I was trying to figure that one out as well. I'd just heard previously (on these forums) that the computer sometimes does that to dump some charge when battery is over full. I'm not sure how it works though, is it just the starting of the motor or does the electric motor try to drive the ICE (as in the ICE really acting as a compression brake with the electric motor trying to "overrun" it and dumping power in the process). That was my best guess anyway.
     
  12. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    I did not propose anything - surely not to jump traffic lights :).

    Well, mine never did that even when I stopped with 8 green bars (and I can recall few occasions when I had to stop on the crossing directly after a steep descent). When I accelerated, I did so solely on the battery and did not have to engage the EV mode. Might possibly have to do something with the firmware, as yours is 4 years older than mine - do not know :).

    But I read about this behavior and it is considered normal, so I would not bother. Look for example here:

    http://www.techno-fandom.org/~hobbit/cars/prius-rally-hints.txt

    Read the 4th article about force-charging the battery. It mentions the behavior you experienced - quoted as "normal". I believe Hobbit also has an 04 Prius...

    Hey, I just remembered something - once when I was driving in the mountains, my good ol' Pri also preferred the ICE, although it had the battery fully charged. It was very hot that day and the car already had more than 200km of hilly ride behind it, so the battery was used extensively. The Battery was hot - I could hear the fans running at the rear of the car - so that was most likely the reason. It also refused to engage the EV mode at that time - however, it would not start the ICE when standing. Everything went back to normal after the battery cooled down. Was your battery hot? Did you hear the fans running?
     
  13. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    Yep, that is the only way I can think of too.
     
  14. uart

    uart Senior Member

    Joined:
    Sep 7, 2009
    4,215
    1,178
    0
    Location:
    Australia
    Vehicle:
    2005 Prius
    I haven't had the Prius for very long so I've only had it up to all 8 green bars a few times. I did stop with all 8 green bars just one other time (again at the bottom of a fairly big hill) but on that occasion it was to turn into a small shopping center car park. So it wasn't really a sudden and complete stop, it was more like slowing to a crawl with all 8 green bars and then driving into the car park and parking, all in electric mode of course. There was no nonsense that time, I just parked it and powered off, did my shopping and when I came back it still had all 8 green bars and drove off all electric. :)
     
  15. dogfriend

    dogfriend Human - Animal Hybrid

    Joined:
    Feb 26, 2007
    7,512
    1,158
    0
    Location:
    Carmichael, CA
    Vehicle:
    2007 Prius

    Toyota has programmed the car to maintain SOC within 40 to 80% of maximum SOC to obtain the longest battery life. When the battery reaches 80% SOC (all green bars) then the car will attempt to lower the SOC to stay in the 40 - 80% range. One method to use battery power is to spin the engine using MG1.
     
  16. spinkao

    spinkao New Member

    Joined:
    Jul 27, 2009
    316
    71
    0
    Location:
    Czech Republic, EU
    Vehicle:
    2008 Prius
    Model:
    N/A
    Thanks, so that's exactly what uart deduced :). Spinning the engine using MG1 makes sense; I thought the ICE was started and running by itself, which would be useless. That's why I did not understand at first.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

    Joined:
    Oct 2, 2004
    40,884
    12,430
    41
    Location:
    Canada
    Vehicle:
    2018 Prius Prime
    Model:
    Technology
    sounds about right although I usually get the other method and that's spinning the engine at high rpm (that's probably because I was coming down the mountainside. You mentioned you were fairly flat except that hill and the traffic light below it). I think I've only seen your situation once or twice (again, because I usually have the bars charged going down the various hills here instead of a flat road).
     
  18. cwerdna

    cwerdna Senior Member

    Joined:
    Sep 4, 2005
    12,539
    2,105
    1
    Location:
    SF Bay Area, CA
    Vehicle:
    2006 Prius
    I've definitely seen it. When I was driving from CA to WA and watching ScanGauge. Normally, if I'm off the gas coasting at highway speeds w/o a hill, I see about 19 or 20 amps of regen (shows ~-20.x BTA) and I can see the ICE is running at low RPMs. When the HV battery got too full, I saw ICE RPMs well >3000 and BTA being positive (no regen, instead a drain). soc was at or a bit above 80%.

    On my new commute, I have to go down a long hill and sometimes the HV batt gets too full (to 80%) and I see the same behavior. Oh well. I wish I had an EV button to drain the batt a bit before starting down the hill.

    edit: Yes, I know this is normal. I just was never able to observe the phenomena myself until I got SG.
     
  19. Matt Herring

    Matt Herring New Member

    Joined:
    Apr 28, 2009
    421
    51
    6
    Location:
    North Andover, MA
    Vehicle:
    2010 Prius
    Model:
    II
    As dogfriend stated this is normal operation of the vehicle when the SOC reaches full bars to protect the battery with ICE burnoff.

    I would much rather have the ICE working to burn off energy than be in a low SOC when the ICE is running to help charge the battery. Not only is the ICE running to charge the battery your power is also drastically reduced when using the GO pedal as power is diverted to recharge the battery. Often times you will see high RPM's in low SOC because of this power diversion.
     
  20. knhobson

    knhobson New Member

    Joined:
    May 15, 2006
    6
    0
    0
    Location:
    Chesterfield, UK
    Vehicle:
    2010 Prius


    I think its all normal.

    It used to happen to me everytime i descended a particular long gradient where the engine would be warm after making an initial climb and the battery would have been reletively low at the top of the hill. By the time I got to the bottom, battery would be fully charged but the ICE would be running. EV would not engage but ICE swithed off after aboyt 400 metres.

    Got to see if the same thing happens with my 3rd gen car which I've only done 600 miles in.

    i'll let you know.
     
Loading...