Hybrid battery gets really low in slick conditions because I'm not braking

Discussion in 'Gen 3 Prius Main Forum' started by ale89515, Jan 23, 2020.

  1. ale89515

    ale89515 New Member

    Joined:
    Jan 23, 2020
    3
    1
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    III
    Hello all, new user here:

    Title basically explains it. When I drive my 2010 Prius in very slick conditions like yesterday, I came home with a very low Hybrid Battery level probably also due to running heater and lights combined with barely braking enough to do any charging through the regenerative brakes.

    I've been driving on standard mode, what is the best way I can prevent this from draining my battery so quickly when it's unsafe to build up speed and brake hard enough to get charge going? I'm talking REALLY slick conditions, freezing rain so I just basically used friction to slow me down more than braking. Does using Power Mode help reduce the draw on the hybrid bat?

    Also I haven't ever used it but I want to try using "B" mode in such conditions to see if I can friction brake better than what I've been doing, but from my understanding that drains energy from the hybrid bat even faster. Should I avoid?

    Thanks.
     
  2. Maarten28

    Maarten28 Active Member

    Joined:
    Jul 13, 2014
    349
    169
    1
    Location:
    Netherlands
    Vehicle:
    2011 Prius
    Model:
    Three
    B mode does not regenerate more energy. It uses energy from the HV battery to run the engine. So that's not your answer.
    I don't know why freezing rain causes you to uses friction braking more than electric braking? Braking lightly will give you 100% electric braking and I would guess that in freezing rain, you are doing that a lot (heavy breaking in slippery situations is a bad idea). Breaking hard will not necessarily generate more energy. When you start using friction brakes (which only happens when braking harder), you will lose some recharge.
    Or do you mean you don't brake at all and only slow down by not pressing the accelerator? That will recharge also. As soon as you get the foot off the accelerator, the car starts regenerating.

    Heater on does not impact HV battery. In fact: it will cause the ICE to run more often, generating a charge for the battery. Lights come from the 12V battery and that needs to be recharged by the HV battery.

    And ultimately: what is the problem? The car wil start the ICE when the HV battery level is too low. It will not break of fail.
     
  3. dubit

    dubit Active Member

    Joined:
    Dec 3, 2016
    764
    470
    20
    Location:
    Indiana
    Vehicle:
    2016 Prius c
    Model:
    Two
    Your Pri's fine and is working just the way it should. My guess is at those low speeds, it didn't have a need to fire up the Engine until the battery required it to do so. I may be wrong here, but you are aware that braking isn't the only way the Prius puts electricity back into that battery...?
     
  4. dig4dirt

    dig4dirt MoonGlow

    Joined:
    Apr 6, 2012
    730
    386
    0
    Location:
    Lancaster Co PA
    Vehicle:
    2014 Prius c
    Model:
    Two
    Don't worry about it. Drive safe.
    In reality the battery is not really low, when it says it's low.

    Again, drive safe!
     
  5. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    85,508
    37,694
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    welcome!
    heat comes from the engine, not battery.

    lights don't use much juice.

    regen works when gas pedal is let up, notjust when pressing brake pedal.

    unless you get warning lights or a message on the screen, everything is fine and operating correctly.

    the computers manage everything for you.
     
    jerrymildred, kc5dlo and kenoarto like this.
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    3,067
    2,873
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    Quit thinking about it and drive! Toyota did a beautiful job automating everything related to underway battery state-of-charge maintenance. It's time to trust them and pay attention to traffic and road conditions instead.

    Overthinking your car can be every bit as distracting as texting behind the wheel.
     
    jerrymildred, kc5dlo, fuzzy1 and 2 others like this.
  7. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    13,134
    6,668
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    Dubit got it right, this happened because you were driving slower.

    Normally, most of traction battery charging comes from the ICE, not from regenerative braking. But when you drove slower due to slick conditions, your propulsion shifted away from ICE power and instead using more EV-only power that drains the battery. And the ICE didn't get run enough to refill it.
    Don't worry about it. The ICE will automatically kick in to prevent it from getting too low. The car's computers have you covered.
     
    jerrymildred likes this.
  8. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

    Joined:
    Oct 17, 2010
    37,713
    26,497
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    I just rolled into the garage with only 2 bars displayed, due to lowish/steady speeds and level roads. Not worried; it'll bounce back.

    And yeah, B is for reducing charging, uses engine braking, most applicable during long hill descents.
     
  9. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    8,756
    5,353
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I'm going to say your Hybrid Battery reading on the lower side of charge probably has little or nothing to do with you "not braking".
    Probably has a LOT more to do with cold freezing rain temperatures, and the slower, careful driving we all do when in that type of environment.

    Pure personal feeling, but I always looked at the regenerative braking system of the Prius as being a brilliant part of the HSD package. But the key word is "part". I'm guessing..yes guessing, that HSD isn't designed to depend on the particular aspect..braking..as being primary to how the system charges or maintains the Hybrid Battery. It almost can't be, because braking IS affected by personal driving habits, and also environment.

    So also IMO, I would actually just ignore the lower state of charge. As long as the system is working, you're getting good MPG, and no battery failure codes, I would chalk up the reality of a generally lower state of charge being displayed, as simply being part of driving in the winter in harsh conditions.

    And in that environment, the priority in HOW you drive, has to be SAFETY, not in maintaining a comforting graphic of green bars.

    If it's anything else? Failure of the Hybrid Battery, 12 volt, speculative etc, etc, etc,...you'll get codes, and you'll know. But IMO as presented, I don't think there really is a problem.
     
  10. Priuslover09

    Priuslover09 Junior Member

    Joined:
    Jan 9, 2020
    232
    25
    0
    Location:
    Dc
    Vehicle:
    2009 Prius
    Model:
    ----USA----
    Do you have the p0A80 code?
     
  11. dubit

    dubit Active Member

    Joined:
    Dec 3, 2016
    764
    470
    20
    Location:
    Indiana
    Vehicle:
    2016 Prius c
    Model:
    Two
    No codes.... He/She was driving in bad weather & at extremely slow speeds. While at those speeds, the vehicle operated in EV mode bringing down the charge in the battery. We "believe" that he/she may be thinking the only way a Prius puts energy back into that battery is by braking.
     
    fuzzy1 likes this.
  12. ale89515

    ale89515 New Member

    Joined:
    Jan 23, 2020
    3
    1
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    III
    Thanks for all the responses, first of all. And I'll readily admit one of the reasons I posted here was to uncover how ignorant I might be about the operation of a Prius, so thanks for that.

    Basically what I gleaned was, even if the battery indicator was very low it's nothing to worry about? That's good to know I suppose; so standard driving mode is still generally the best in very slick conditions?

    The only other thing I'd mention as an issue is my 12v battery may not be the healthiest; I'm driving a used vehicle that was owned for about 1.5 years, I've been driving it for the same amount of time, and recently I've had a problem with the 12v battery being totally dead if I didn't drive for about a week. After doing research I remedied this by buying a trickle charging battery maintainer that seems to be working like a charm, but I have noticed thanks to using it that my 12v battery is dipping under 50% charge level in less than a week of little to no driving which to me seems to be an indicator I could stand to replace it. I read that the Prius's OEM 12v battery is poor quality and lasts only about 4 years so I'm wondering if my trickle charger is just life support for it at this point.

    Otherwise thanks for the responses guys. Good to learn what actually powers the various accessories in a Prius, very informative.
     
    dubit likes this.
  13. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

    Joined:
    Oct 17, 2010
    37,713
    26,497
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Have your 12 volt battery checked with an electronic load tester. Or you can DIY with something like Solar BA9.
     
  14. The Electric Me

    The Electric Me Go Speed Go!

    Joined:
    May 22, 2009
    8,756
    5,353
    0
    Location:
    Undisclosed Location
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    I would just replace the 12 volt battery.
     
  15. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    13,134
    6,668
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    The battery indicator should be 2 bars or higher. So don't worry unless you see just 1 bar.

    As far as the car is concerned in slick conditions, the mode doesn't matter. Use whatever feels best for you.
     
    Mendel Leisk likes this.
  16. Priuslover09

    Priuslover09 Junior Member

    Joined:
    Jan 9, 2020
    232
    25
    0
    Location:
    Dc
    Vehicle:
    2009 Prius
    Model:
    ----USA----
    Does car the have any signs of 12v overheating?
     
  17. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

    Joined:
    May 12, 2018
    3,067
    2,873
    1
    Location:
    Pennsylvania
    Vehicle:
    2018 Prius c
    Model:
    Two
    I don't mean to hijack the thread, but I'm really curious. Does a 3rd generation Prius (like OP's 2010) always show the hybrid battery charge on the dash display?

    Our Prius c will show it if we select that display out of the 5 or 6 available, but we never actually do that in ours apart from maybe 20 minutes on the first day we had the car.
     
  18. Priuslover09

    Priuslover09 Junior Member

    Joined:
    Jan 9, 2020
    232
    25
    0
    Location:
    Dc
    Vehicle:
    2009 Prius
    Model:
    ----USA----
    I think it does actually show thee battery on the dash
     
  19. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    13,134
    6,668
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    Gen3 Liftbacks have a permanent SOC (state of charge) gauge, separate from the user selectable displays.
     
  20. ale89515

    ale89515 New Member

    Joined:
    Jan 23, 2020
    3
    1
    0
    Location:
    USA
    Vehicle:
    2010 Prius
    Model:
    III
    The battery level indicator is one of the display options you can choose from, I just happen to like it and (previous) I thought it was important to keep an eye on the level.
     
Loading...