Prius Coasting

[terkar]

Is it just me or....

When coasting to a stop it I seem to hear a slight grinding (Not a bad grinding) as though two plates are being rubbed together. Seems to really slow the prius down as opposed to a freewheeling coast. Has anyone else noticed this? Could it be the Planatary Gears?

My old 94 Explorer coasts much easier i.e. doesn't seem to slow down like the prius.

[Danny]

It could be the process of turning that energy into energy to charge the battery back up.

John or someone else more technical know?

[htmlspinnr]

1 word: Regeneration

[Danny]

1 word: Regeneration

Rick with his fancy terminology!

[efusco]

It is, indeed, regeneration. You can begin to predict how much braking will be done by the regeneration with time and find that you can slow to a near stop without touching the brake at all.

I have also found that by VERY lightly depressing the accelerator that you can disengage regeneration while still not draining power from the battery to drive the wheels or turning on the ICE. This essentially allows you to free-wheel. I tend to do that on uphill areas where I need to coast to a stop. My options in those cases are to use power to climb or brake hard when I get to the top if I don't free-wheel coast. You don't regen anything, but you don't lose anything either. This takes practice and it really helps to watch the energy screen to help you learn when you've 'hit the sweet spot' b/w regen and powering the wheels.

[Jerry P]

That regenerator sound is one of the sweetest sounds the Prius makes!! I have wondered why there are no regen units on the back axle/brakes. If we're out to capture wasted energy, why not go for all of it?? Maybe someone knows why Toyota did not opt for this.

[efusco]

That regenerator sound is one of the sweetest sounds the Prius makes!! I have wondered why there are no regen units on the back axle/brakes. If we're out to capture wasted energy, why not go for all of it?? Maybe someone knows why Toyota did not opt for this.

Jerry,
If the car is stopped by regeneration be it by 1 wheel, 2, or 4 all of the available kinetic energy IS recaptured. It would increase the complexity without increasing regeneration. You don't need all 4 wheels to do it. The key is that the friction brakes mustn't engage, and, if I understand it correctly, the friction brakes don't kick in until needed.

[SpartanPrius]

The key is that the friction brakes mustn't engage, and, if I understand it correctly, the friction brakes don't kick in until needed.

By friction brake, I assume you mean the applied disc / drum brakes. Correct me if I'm wrong here. Doesn't the Prius regeneration system attempt to capitalize from the slowing of the vehicle. If you were on the flat, or going uphill, it shouldn't seek to regenerate unless you signify you are intending to slow down (i.e., apply the brakes). Even then, it should assist the brakes without taking a leading role. For instance, the harder you brake the more of the sloughed off kinetic energy it will attempt to capture. This in turn should help your braking action by applying an assist.

Now, when you are rolling downhill, I can see the system engaging progressively to check any increase in speed, which is a nice safety bonus, assuming you aren't already going too fast! Other than that, application of regeneration when you are "freewheeling" appears counterintuitive to a hybrid / high mileage design.

And besides, how dare it intrude upon my fun! :guns:

It is logical to recapture the energy using the front drive wheels since, 1.) they are already hooked to the generator / motor; 2.) there is more weight on these wheels coupled with the weight shift that occurs under braking; and, 3.) the rear wheels would be very likely to lock under harder braking or poor surface traction (you'd be into ABS A LOT).[/b]

[efusco]

By friction brake, I assume you mean the applied disc / drum brakes. Correct me if I'm wrong here. Doesn't the Prius regeneration system attempt to capitalize from the slowing of the vehicle. If you were on the flat, or going uphill, it shouldn't seek to regenerate unless you signify you are intending to slow down (i.e., apply the brakes). Even then, it should assist the brakes without taking a leading role. For instance, the harder you brake the more of the sloughed off kinetic energy it will attempt to capture. This in turn should help your braking action by applying an assist.

Ummm, I think you're wrong. The regen braking kicks in any time the accelerator is released completely, and it's not an intelligent regen--that is, it's the same amount if your on the flat, down hill, or up hill. I could be wrong, but that's my take and experience.
--evan

[SpartanPrius]

That is disappointing. I speak from no direct experience, of course, but I do believe that would be a better setup. Freewheeling is the ultimate fuel conservation. Granted, if the battery is in need of charging than regen should kick in. And before someone says, "It always needs recharging!", I think it could be as you say, more "intelligent".