Bmode and better regen

Discussion in 'Prime Main Forum (2017-Current)' started by isakprius, Dec 28, 2019.

  1. fuzzy1

    fuzzy1 Senior Member

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    This shouldn't happen, unless there is some change that I missed. MG1 has a fixed ratio to the wheels, and simply can't overspeed without exceeding the electronic speed limiter set (for flat roads) at something over 100 mph.

    MG2 will overspeed only when the ICE is off, not spinning, and the safe threshold speed for the Prime has been boosted quite high (to 80 mph???), well above Gens 1-3. With ICE spinning, MG2 is safe in all Prii generations, at least while under the electronic speed limiter.
     
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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    If you step on the brake pedal while in any drive mode with a full battery, you'll be getting friction brakes because there's no way to store the energy that would be recovered by regen braking.

    If you use B during a long hill descent, you get the gentle charge rate that you've documented. The car has no idea how long the descent will continue, so they've programmed it to make that drag effect last as long as possible. The reduced charge rate also causes less heating in the battery, which is better for long-term health. Lower temps also leave the battery more ready for a heavy draw to climb the next hill.

    By leaving it in B mode during the descent, the car is less likely to require brake pedal input in the first place. Also the computer is primed to divert torque into the gas engine for compression braking, which provides drag but does not depend on battery status. If the battery fills up, overheats or fails while you are halfway down the hill in B mode, the gas engine will still provide enough drag to prevent a runaway. If that happens in D mode, it's on you to figure out the situation and react to the problem, hopefully without burning your pads & rotors into ash.

    If you find that your use of B mode is not recovering as much energy as D + some pedal action per descent, then you are probably using it on flatter or lower hills than the situation it was designed for.
     
    #22 Leadfoot J. McCoalroller, Dec 29, 2019
    Last edited: Dec 29, 2019
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  3. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Maybe that should be printed out and tucked into the Owner's Manual, to supplant the cryptic explanation Toyota came up with.
     
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