Prime Auto Activating Charge Mode

Discussion in 'Prime Technical Discussion' started by drash, May 24, 2020.

  1. drash

    drash Senior Member

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    Has this happened to anyone? I was driving through the city with a depleted battery last night when the engine came on, of course. While I was driving I noticed my EV range going up from 0 rather dramatically. I forced my Prime into EV mode by hitting the EV Auto button after it registered 1.6 miles EV. By the time I pulled into my house I had 1.3 mile EV range left. The CHG light was not on nor did I select it. The only thing I can think of, I never adjusted the accelerator because I was in a single low speed area with no stop lights. No it’s never happened before.


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  2. schja01

    schja01 One of very few in Chicagoland

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    I haven’t driven my prime lately. I took it for a drive in HV mode in the early morning. I had 16.7 mpg on the guess-o-meter. When I returned after 15 miles I had 18 EV miles. No wind no traffic to speak of here in flatland.
     
  3. Bob Comer

    Bob Comer Active Member

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    I drive in HV more than half of my commute, and yes, the EV mile display goes up a bit if it was depleted, but I've never had it go up 2 miles, it always stays in the 1.something range. No clue why it does that, but it doesn't feel like it's charge mode.
     
  4. EdPalmer42

    EdPalmer42 New Member

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    If the engine starts, it has to go through a warmup cycle before it will shutdown. This takes at least a few minutes and uses more gas than just running for a few minutes. Cruising at a low, constant speed uses the least possible amount of gas. Maybe if the car decides that it's using more gas than it needs to move the car, it will charge the battery rather than waste the energy.
     
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  5. Salamander_King

    Salamander_King Senior Member

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    Charging a traction battery without using CHARGE mode is possible. I have demonstrated this charging capability on a different thread. In summary, I intentionally drove to maximize regen braking. With more HV acceleration out of EV range followed by coasting to charge the battery, I was able to replenish 9% SOC (91% to 100%) and 3.1miles gain on GOM on a single ~18 miles commuting drive by force-feeding the traction battery using regenerative braking on HV mode.
    MPG in Hybrid Mode | Page 6 | PriusChat

    However, my experience has been that this only works if there is some EV range left in the traction battery. Once EV range is depleted, force charging the traction battery using regenerative braking only (no CHARGE mode) was not possible (or at least very difficult). So, what you have observed is something new to me.
     
    #5 Salamander_King, May 25, 2020
    Last edited: May 25, 2020
  6. jerrymildred

    jerrymildred Senior Member

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    This seems to me like the most likely explanation. The steady low speed being the main factor. If moving the car won't put enough load on the engine to warm it up in an appropriate amount of time, then increase the load by charging the battery. If such a place existed in my world, I'd give it a try to see if I could duplicate the experience.
     
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  7. drash

    drash Senior Member

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    Well the engine had already been running and had been shut off so it had been in hybrid mode for a good 3 minutes before this started. I was using battery only in hybrid mode for what seemed a good 3 minutes through a lot of traffic lights before the engine fired up to charge my battery.

    Just as likely I haven’t been driving it and let it sit on an empty battery for days (odd seeing 0.0 miles/kWh for every day) while WFH. Charged it up earlier that AM and went grocery shopping. Registered a 5.1 miles/kWh and had 3.2 miles EV left before running the second set of chores on just that (yes I did that on purpose). Might be a computer glitch, because just as it hit 0.1 miles EV, it jumped to 0.3 miles and then went into hybrid mode after that was depleted. Now that I think about it, maybe I should put my 12V battery charger on it.


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