Using "B" for dynamic braking

<div class='quotetop'>QUOTE(efusco @ Nov 5 2007, 09:26 AM) [snapback]534960[/snapback]</div>

B-mode does allow you to brake (to some degree) without your brake lights turning on. This can be useful for slowing down subtly around speed traps. I'm not advocating that use, simply pointing another possible benefit.

 

<div class='quotetop'>QUOTE(seasalsa @ Nov 5 2007, 10:47 AM) [snapback]534932[/snapback]</div>

that is halarious~! I have 1 question, will it screw up my battery if i keep overflowing my battery? (i never used the "b" gear yet.

 

<div class='quotetop'>QUOTE(bluemoonseller @ Nov 9 2007, 07:07 PM) [snapback]537459[/snapback]</div>

No, you won't "overflow" or overcharge it, or even come close. The car's computer is very protective of the battery and allows it to charge no higher than about 80% (eight green bars on the battery display). I've seen it as high as 82% (read via CAN-View) as I've descended a mountain road.

 

<div class='quotetop'>QUOTE(Spike Jones @ Nov 5 2007, 07:21 AM) [snapback]534915[/snapback]</div>

While there is some regen in B mode, it is LESS than using the brake pedal in D mode.

There are only three conditions when using the brake pedal applies friction braking:

1. Panic stop: You press the brake pedal very hard.
2. Very slow speed: below 9 (?) mph.
3. If the battery is as full as the computer wants to allow it to get.

Otherwise pressing on the brake pedal uses motor-generator 2 (MG2) to slow the car by generating electricity to re-charge the battery. Thus the ONLY time you want to avoid using the brake pedal is for number 3: when the battery is full.

This happens on long steep downhill slopes. And thus that is the only time you should ever use B mode.

It is true that using B mode will cause the car to slow more when you take your foot off the accelerator. But you can accomplish that by stepping on the brake. B mode wastes energy. The brake pedal recaptures energy.

The Energy screen will show regen, but does not show the amount of regen. Those of us who have the CAN-View can see the actual amount of regen, and as Evan documents above, there is MORE regen with the brake pedal than with B mode. And you are NOT using your brake lining when you step on the brake pedal except under the unusual conditions noted above.

 

After reading up on "B-Mode" here on PC, and reading the VERY informative hobbit write up on the subject, I now understand what exactly "B-Mode" does, what it is supposed to be used for, and how.

My question is: Is there a maximum allowable speed limit I should be aware of, when I should not slap the car into B from D?

(for example and clarification: I would never throw a manual trans into a lower gear like 2nd at 60mph and 5th, unless I wanted to red-line...does the same rule apply to the Prius...)

Dave

 

You can switch to B mode at any speed. The computer will not let you cause a problem.

Tom

 

Clarification: the prius does not have a normal transmission. All the gears are always connected, so it is not possible to redline the prius engine.

However, I should point out that is IS possible to redline the electric motors by switching into neutral when the engine is off and then coasting down a hill to a speed above say... 55mph. There is no danger of redlining anything if the engine is on when you shift into neutral.

 

Got it...Thankyou.

 

"B" mode

Sorry for this: this whole post implies (by omission of an explanation" that what "B" mode is should be obvious. I have a new 2008 Prius, my gearshift has P for park, N for Neutral, R for Reverse, and D for Drive. It also has a "Park" button to hold the car in park (supposedly for long times spent parked) and a parking brake. No "B" mode that I'm aware of though I now realize my salesman knew nothing about the Prius. Am I missing something obvious, or could this be something left off the 2008 model. Thanks.

 

As far as I know the 2008 model has it too. I haven't heard that that's changed. Check your dash display where P, N, & D are pictured; it should be to the lower right, below P. Pushing the shift lever straight down should engage it.

See this for a full description of its operation.

 

You've taught me something new (for the 1674th time ). I had never noticed this before, so I just went out to check. You are correct that you need to be in D for B to appear on the display. It doesn't show when you're in P, N, or R.

So to modify my previous response: Pushing the shift lever straight down while in D should engage it.

 

Well I'll be

There it is - just didn't look at it before because all the other gears are off to the left. thanks.