EV mode shuts off after about 5 miles/10minutes

Discussion in 'Prime Main Forum (2017-Current)' started by Hempy7777, Oct 8, 2019.

  1. Hempy7777

    Hempy7777 New Member

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    Sorry if this has been asked, I have looked but didn’t find a good answer/explanation. I live at about 7300 ft elevation and it is starting to get pretty cold in the morning. When I leave to go to work in the morning my car, usually at 100% charge starts in ev mode and stays in ev mode until I get to about 5 miles, during this time I am always going down hill, and then shuts off, the car on the screen doesn’t show ev any more and I feel the distinct change from ev to hybrid.
    I am not sure if this is related to the temp. I do not have defrost on, that was one of the first things I figured out reading the forum and I do have the heat on but not very high.
    Any suggestions? The thing that really throws me is the going down hill, I usually gain 10% charge or more down the hill and still do but start using gas. When I head home the car does start and stay in ev mode but it is also I. The 50-60 range in the afternoon.
     
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    It sounds like it's the "going downhill with a full battery" part.

    If you can, try and leave with some buffer room (e.g. set the timer for, maybe, 40-50 minutes before after you actually leave. Note that the car usually finishes charging about 30 minutes prior to the set departure time.)

    Edit: I meant after the scheduled time so it doesn’t quite finish before you leave so you have a buffer.
     
    #2 Tideland Prius, Oct 8, 2019
    Last edited: Oct 10, 2019
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  3. bisco

    bisco cookie crumbler

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    welcome!

    it is both the temp and the full battery. experiment with tidelands advice, you might find a sweet spot where you end the downhill portion close to full, and you're paying less for wall charge.
     
  4. Hempy7777

    Hempy7777 New Member

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    It is actually scheduled to finish charging at 5:45 and I have been leaving at 7 because I am being lazy and not going to the gym. I am not using climate control if I do will that help? I travel about 2.5 miles on relatively flat roads prior to the down hill portion.
     
  5. Tideland Prius

    Tideland Prius Moderator of the North
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    Oh shoot. I meant to say set it to 40-50 minutes after you leave so that it’s not quite finished before you leave so that you have some buffer.

    Sorry, I got it backwards in my previous post.

    If you set it to 7:40, it’ll typically be done by 7:10. But you leave at 7, so the car should be around 90-95% by the time you leave. That plus the 2.5 miles may be enough of a buffer.
     
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  6. Trollbait

    Trollbait It's a D&D thing

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    It is the battery being fully charged before going downhill that is likely the main cause.

    Toyota hybrids, plug or not, spin up the engine once the battery reaches full from regenerative braking in order to get rid of the excess energy. Fuel isn't actually being used, but with the Prime, once the engine starts spinning for the first time on a trip, the car goes into hybrid mode to complete a warm up cycle.

    If you don't want the car going into hybrid mode, don't charge it up all the way, as has been explained. Depending on the length of your commute, you could just live with it, and take advantage of extra cabin heat, as your EV range drops with the colder temps.
     
  7. Hempy7777

    Hempy7777 New Member

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    Got it thanks for your help! I didn’t charge last night and it stayed in ev mode the whole time

     
  8. mister2cool

    mister2cool Junior Member

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    So I just had this happen to me twice already after going down a steep hill in B. The hill isn't terribly (~1/2 mile) long but suppose to be the 2nd steepest in the state of NJ and that road gets closed almost every time it snows. When the car reached the bottom, EV mode turned off and ICE came on for the next ~4 miles until I slowed down to a stop before it changed back to EV only. The battery was around 80% before the hill and only increased a few percentage at the bottom and it definitely wasn't close to being full.

    In a post on facebook on this topic, I thought it might have to do with safety to prevent a runaway car in the event of a failure. I no longer think that's the case since ICE didn't start until I have stopped at the bottom of the hill. I am wondering if this has to do with temp of battery after rapid charging from regenerative braking. When I had my Gen II the hill always charged the battery to green every time and I could drive the next mile or so completely on battery if I take the local route so it's somewhat a significant charge in a short amount of time. I am sure it heats up the battery quite a bit so it may not be safe to discharge in EV mode, which would most likely heat up the battery even more.
     
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  9. m8547

    m8547 Active Member

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    Yes, it's something to do with charging the battery too fast or for too long. But the battery doesn't get very hot, so it's not usually for temperature.

    The engine was probably on on the way down and you just didn't notice until the bottom of the hill.
     
  10. mister2cool

    mister2cool Junior Member

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    Went down the hill again in B today.. 70% at the top of the hill, 75% at the bottom, in the span of under 60 seconds. Sure enough, EV turned off at the bottom of the hill and ICE started.
    5% increase in charge in under 60 seconds is some seriously impressive charging rate, and I can't believe battery doesn't get hot with that kind of charging. I am convinced that this behavior is to protect battery from overheating.

    On the flip side, that damn hill took 15% battery to climb back up....
     
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  11. Ronald Doles

    Ronald Doles Member

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    I have a Prius V with a ScanGauge installed and monitor battery current. I have observed battery current is limited to around 110 amps in either charge or discharge mode. No matter how hard you brake, the current is limited at around 110 amps and if any additional braking is required, it comes from the mechanical brakes. This current limit would extend the life of the battery. I would think that the Prime with it's larger battery also has a current limit that is designed so that you can't hurt the battery.

    I don't know what would happen if the hill was steep enough for the regenerative braking to exceed the 110 amp limit or long enough for the battery to reach a fully charged state.
     
    #11 Ronald Doles, Nov 23, 2019
    Last edited: Nov 23, 2019
  12. jerrymildred

    jerrymildred Senior Member

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    I'm sure that's what it is. I had something similar happen on vacation in Colorado going down Grand Mesa. It took longer because it wasn't super steep, but it was several thousand feet. ICE came on at about 98% charge, so it didn't hurt much. Aside from that brief engine run, I went something like 50 continuous miles in EV. LOL!
     
  13. mister2cool

    mister2cool Junior Member

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    Not sure I follow what you are trying to say. Yes I am aware that mechanical braking is applied when needed. I am sure there is a current limit, otherwise the battery would be a ticking bomb. 110 amps at 350v is 38kw and I am sure plenty of heat is generated no matter which direction.
     
  14. Martin Spahn

    Martin Spahn New Member

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    Hi Hempy7777, I share your issue, and can relate.
    I bought my used 2017 Prime and started driving in early October. I live at about 4500 ft elevation, and commute to work down to about 3200 ft elevation, and run into the identical issue. No matter what I have tried, I cannot get the car to stay in EV during the steep downhill, and it takes a while down in town to get back into EV, during which time we burn gasoline, which is frustrating and should be avoidable.
    Even when I stay away from defrost, this happens. Anytime I start using defrost or heat, the car switches out of EV.
    I can assure you that I am about 3-4 miles down from full charge (for example, starting at 25full, starting the downhill at about 21indicated or 22indicated electrical range) when this happens, so I doubt that the "not-fully-charging-approach" is going to fix this issue.
    Using the engine break during the downhill does not prevent this.
    Staying well under the 50mph speed limit does not prevent this.
    Lightly staying on the break (which I hate doing because it wears breaks unnecessarily) the entire way down or intermittently does not prevent this.
    A bit frustrating, as my "prime" goal is to commute purely electrical. I would think that this shoud not be disallowed by the design, even during cold weather. And yes, the colder it gets, the more this issue shows up.

    Pulling over, stopping, turning the car off, and restarting the drive: that seems the only way to get back into EV immediately.

    Seems strange to me. My 2005 Prius always topped off its battery charge towards the end of the downhill, resulting in that high revving engine sound (nowhere else to go for the kinetic energy) that "us downhill commuters" are familiar with...

    Everybody, please chime in with possible fixes: has anybody figured out how to better "force" the car to strictly stay in EV?
     
    #14 Martin Spahn, Nov 25, 2019
    Last edited by a moderator: Nov 25, 2019
  15. jerrymildred

    jerrymildred Senior Member

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    Hey Martin. Welcome!
    First off, staying lightly on the brakes (not "breaks") won't wear them out because it's slowing the car using regeneration just like it would in B mode. You have to press fairly hard to engage the friction brakes. That's one of the ways the Prius saves a ton of gas. So don't let that bother you, although, B mode does make those long hills a little easier.

    I'll assume you're in EV and not EV Auto, since EV is the default startup mode. And I'll assume you're staying under 84 mph. :D

    How cold are you talking about? If it's very cold and you're calling for more heat than the heat pump can generate, that's a very likely cause of the ICE starting up. Also, if the hybrid system itself is too cold, the ICE will start.

    The manual lists other conditions that I don't think apply here, but it also says that there can be other things besides what's in the manual. All that info is on page 87 of my '17 Prime manual.

    My theory is that the system is cold and your descent is generating more energy than the hybrid system can handle in those temperatures.

    But a second theory is that you actually have filled the battery. You said what the remaining miles were when you started down the hill, but you can regenerate quite a bit with a 1,300 foot drop. What does the state of charge (percent, not miles) actually read when the ICE starts up? I'm guessing that before you get to the bottom that battery is at least nearly full.

    Hope this helps. (y)
     
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