shift to B mode for more regen under ~21mph

I often do the same thing. It makes it easy to control deceleration with just one pedal. My problem is sometimes forgetting to put it back in D for accelerating.

 

Very interesting. I must try it.

 

Good info but i must say it was the title of this thread that grabbed my attention.

 

B mode always involves LESS regen, so the title is inadvertently right. B mode is designed to throw away energy, never go there unless you have energy you want to dissipate.

http://www.techno-fandom.org/~hobbit/cars/b-mode.html

 

Ditto! Got to love those occasional typos.

 

I have been shifting to B for a while now. I use it to keep the car from losing regen when going over pot holes. If you go over a pot hole while riding the brake traction control wants to kick in and you lose the regen. If I use B below 20mph it usually wont lose any regen when going over the pot holes.

 

Not sure how, but I missed the typo first time around.

Not always. At speeds below 20 MPH the ICE doesn't spin and the slowing effect is entirely from regen. So if there is a need to brake anyway, there is no waste of energy. From Hobbit's paper:

Under 20 mph, if the engine is not already running and your foot comes
off the accelerator, B mode simply regenerates reasonably heavily [30A or
so] into the battery. This drops off around 12 mph to a lower current,
and is then similar to being in D until regen capability kicks out entirely
around 7 mph. So between 19 and maybe 10 miles per hour, you can use "B"
to slow down in an energy-productive way, and essentially drive around in
electric-only mode with one pedal ....​

 

I think you mis-interpret Hobbit's data. Your assertion is incorrect. Iff your in EV mode, B-gear below 31 KPH (~20 mph) will indeed cut off the ICE and increase regen when the brakes are not applied. Basically its a harder coasting decel. I have amp meters that will register this quite clearly.

I don't think it does anything special with brake pedal regen though. You can get the same regen in D simply by applying more brake pedal pressure. The B-gear coasting decel is definitely smoother and fun to surprise tailgaters with (warning... no brake lights!).

11011011

 

This is the key paragraph. B mode doesn't allow for any more regeneration, unless perhaps at the very high end, but you can do it with one foot. Whether it's worth shifting for that "benefit" is a matter of personal preference.

Tom

 

Not true. B does allow more regen on a coasting decel while the vehicle is in EV mode and the speed is below 20 mph.

The OP is correct, your assertion that B doesn't allow for greater regen needs to be qualified by "B doesn't allow greater regen while significant brake pedal pressure is applied at speeds above 20 mph"

Absolutes don't work with this axiom in in either case.

11011011

 

You took my post out of context. I clearly stated that the advantage to B mode is that you can do it with one foot, or in other words while coasting. However, that said, absolutes absolutely work in this case. Maximum regen is limited by the ability of the battery to absorb energy, which is the same whether in B or D mode.

Tom

 

This part is true. Pressing the brake pedal causes the brakes to move into a ready position. Because the pads are now touching, there is a small but finite increase in friction, which makes your statement factually correct even if not physically significant.

The increase in regen is only an increase in coasting regen. Applying brake pressure will increase regen to the same level.

Tom

 

Agreed.

I miss-understood your one-foot = coasting. I think of coasting as a no-foot driving technique B). Thanks for the clarifications... You are correct

11011011

 

Thanks. We can get into some real technical nick picking with the Prius, but then that's why it's so much fun for technical people.

Tom

 

This maybe an interesting "Did you know....?" info.
However; how practical (or will you bother) to shift into B under 20mph everytime you're slowing down?

Also, what's the reason to be afraid of using more Brake Padel action anyway?
As stated, the Prius OS already programmed to do heavier regen while you're on slight braking action (to counter the real use of the brake pads)....But even that, Brake Pads are cheap to replace anyway!

So if you're concerned about wear the brake pads, maybe you should be more concerned about 'wearing' out the gear-shift joystick when shifting to B everytime slower than 20mph. (It's an expensive item to replace) Suddenly, wearing out the brake pads will make more financial sense.

 

Nice thread, and I thought I'd interject, thanks to whomever put the "F" back in the title. I guess it wasn't just a Dutch thing..........

 

Below 7mph, there is no regen braking.

Ken@Japan