How Often Do You Use the Braking Feature on Trans Shifter

On flat ground, B mode saves nothing that cannot be saved with a well controlled light to moderate touch on the brake pedal, but it does waste some regen energy that could have been put into the traction battery. This waste cuts overall MPG slightly.

On mountain descents of more than roughly 600 vertical feet at slopes greater than about 2%, B mode saves on brake pad wear and heating. The wear alone is not a big deal, as brake pads are cheap. But somewhere past roughly 1000 vertical feet, brake overheating does become a safety issue.

This numbers are very coarse estimates for the Liftback. I haven't seen anyone confirm or refigure them for the 'C'.

 

The c has a smaller HV Battery, so it will take less of a hill to fill it, B mode is only good for long hills, but in a c, they do not need to be as long.

So long as you do not mind what your MPG is, you may use it anytime.
I use it in the Great Smokeys but have not needed it in the Ozarks.

 

I checked out the B position a few times on the local hill-t0-traffic lights, and found that I liked just using the brake.
Not sure what the mpg gain or loss would be, but since got rid of my last standard shift in 2009, I'm spoiled. Never going back to shifting while moving.

 

This is the wrong way to use it. You aren't saving the brakes or increasing regeneration. In this sort of braking situation just press the brake pedal and it will accomplish what you are trying to do, but do it better.

B Mode is for long downhills where the HV battery will max out. B Mode throws away energy, forestalling the point where the HV battery reaches the high limit and ends regenerative braking, thereby saving wear on the friction brakes.

If you don't drive in the mountains, you probably don't need B Mode.

Tom

 

I'm not yet convinced that my repeated use of B-mode for steep 3000 to 5000 foot descents, with the engine spun up to 4600 RPM for extended periods, is low stress. But that is was it is made for, to keep the brakes from overheating and failing.

On flat land, you could use B-mode full time and it should still be low stress compared to my occasional mountain descents. No benefit, but no harm beyond some mpg loss.

Depending on the situation, B-mode should produce a slight mpg loss, or be a wash, compared to using the brake pedal. It should never produce an mpg gain unless the driver has a hard brake foot style that defeats regeneration.

 

the B mode is always misunderstood as people think it's a good thing and gives you more regen.. that idea is out there and so many people to this day still believe it.

indeed it throws away energy.. wastes it.. and the regen you get from just using your own foot would be better.

what B mode is for.. is yes.. very, very long downhill grades where the traction battery would be filled up already.. and it'll help prevent your friction brakes from overheating.. that's really it. no one should shift into B otherwise.

 

I know in my Gen II the battery does not regenerate in B. This is the same for the C? I have not even tried B yet in my C come to think of it.

 

It may depend on which Gen prius you are talking about.

Clearly from all the posts about "B", if you are under 35mph and on flat ground the only difference between "D" and "B" is the computer is more aggressive with regen. Anyone can easily see this by trying it rolling up to a stop light. In "B" mode the 30% regen stops a lot quicker, and may be too quickly and you risk getting rear ended for not having any brake lights on. However, in most cases you will slow down complete without using the brakes at all in either "D" or "B" if you have enough distance and a light touch on the pedal and the "B" mode usually means you have to creep up further and waste battery driving up to the light.

This may mostly apply to the Gen 1, and the more modern prius are much smarter about the regen braking and there is no reason to use "B" unless you need some ICE friction for hills.

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

But yes, in some older prius you can use it to regen more and brake less at the expense of possible heating up MG1 more and also risking getting rear ended. However when you press on the brakes at all, "D" and "B" are exactly the same under 20mph. It can be used for coasting to a stop, or it can be used for hills. And for Gen 2 on up it might only be useful for hills.

 

I have not found B-mode to slow down my Gen3s any faster than a downshift in nonhybrids. This is a common maneuver in manual transmissions, and also possible (but not so common) in traditional automatic transmissions, neither of which turn on the brakes lights.

Getting rear-ended in this situation is a result of extreme tailgating or extreme driver inattention (i.e. texting) of the driver behind, not failure to turn on the brake lights.

 

I agree but the distance away from a light where I might use "B" mode is further away then you would downshift. So in the place where you might expect a manual car to coast in the hybrid the regen braking does slow as fast as someone aggressively downshifting which is more unusual behavior. ie. if you downshifted that far away you would end up having to give it gas to get back up to the light.

I was just saying that a light tap on the brake in "D" mode is safer regarding being rear ended. And it is more akin to downshifting and taking foot all the way off the clutch immediately instead of gradually. (well maybe not 1st gear)

 

I tried the B position yesterday to see what it was all about. I don't see any use for it in my area. It won't get used.

 

I am totally wrong on this. The C does regenerate when in B mode. Learned this yesterday on my way home form work.

 

There must be something wrong with your Gen II, although more likely your test methods are suspect. B Mode in the Gen II does indeed produce regeneration, but in most cases also discards a portion of the charge through engine braking.

Tom

 

Nope, it is just that I am wrong in what I remembered about my Gen II.

 

i use B often when slowing for traffic conditions, it saves on the the brake pads, and like it says above assists in charging the battery, i have read a few threads on this, comments like," i want people behind me to know i am braking" do not make sense as they would'nt know if you was changing down gears in a manual, also using the foot brake at freeway speeds causes excessive heat and therefore premature wear on both brake pads and discs, so this would be another instance to use B mode

 

B mode does not assist in charging the battery... in fact it has the opposite effect - it throws away energy. In traffic you should simply try to brake such that the blue bar on the HSI comes close to but not quite the bottom of the scale. That will maximise regenerative braking without using your brake pads or wasting energy with B mode.

 

You are totally wrong. I have a Scangauge that is set up to read battery charging amps and it shows good current going into the battery when slowing down in B mode. More current than you would have when slowing down in D.
Where did you get your info?
X

 

I won't even mention that the coasting charging bars (the ones UNDER the neutral line on the graph) easily double when using B mode. It appears as if the B mode is simply a switch that makes a more aggressive recoup of energy when coasting, thus acting like a low-gear-deceleration aid.

Couldn't tell you if it's true, but if it were that's what it would look like...