Can you use the B mode too much?

You can use it to brake, but it's not as efficient as using the brake for that purpose. In other words, you're not going to hurt anything except your gas mileage by using it.

After a long down hill, you have to manually shift it back into D.

 

<div class='quotetop'>QUOTE(Betelgeuse @ Apr 30 2006, 06:46 PM) [snapback]247673[/snapback]</div>

Yep. Not worth it. Use your brakes and avoid the hassle. The Prius will use engine braking if you top off your battery so you really should never use it. Or in other words, once is too much

 

I would guess that one legitimate reason to use B over regen braking is if you're going down a super long hill, and if you regen brake you will max out the SOC before the halfway point. B would be a good way to get some regen and also limit the speed without filling up the HV battery too early.

 

<div class='quotetop'>QUOTE(jimgraffam @ Apr 30 2006, 05:12 PM) [snapback]247692[/snapback]</div>

If less than 20MPH "B" mode will maximise regen and not use engine braking when coming to a stop. Try it.

 

<div class='quotetop'>QUOTE(burritos @ Apr 30 2006, 05:16 PM) [snapback]247693[/snapback]</div>

In a 'normal' car you would use the lower gears (which Toyota calls 'B') to use the engine to break which 1) Prevents Brakes from overheating, and 2) Saves brake pad life.

I would assume the same applies to the Prius, if not true please let us know.....

 

<div class='quotetop'>QUOTE(j24816 @ Apr 30 2006, 05:58 PM) [snapback]247705[/snapback]</div>

Not true.

The prius does not use the friction brakes at over about 9 MPH except for a panic stop situation.

The real reason for B was explained by Presto in his post.

"one legitimate reason to use B over regen braking is if you're going down a super long hill, and if you regen brake you will max out the SOC before the halfway point. B would be a good way to get some regen and also limit the speed without filling up the HV battery too early."

 

<div class='quotetop'>QUOTE(j24816 @ Apr 30 2006, 08:58 PM) [snapback]247705[/snapback]</div>

This is true. For normal breaking, just use the break pedal, and the Prius will do regen breaking unless you panic stop. For a long downhill, the traction battery will charge up and then the hydraulic breaks will have to take the load. 'B' mode is just like downshifting with a manual transmission, with the added touch that the valve timing is shifted to create maximum engine drag.

In short, use 'B' when you want to throw away energy, which is normally on very long downhills.

And yes, you have to shift back into 'D' when you are done with 'B'.

Tom

 

<div class='quotetop'>QUOTE(burritos @ Apr 30 2006, 03:36 PM) [snapback]247669[/snapback]</div>

Where are you? Just some vague idea. What kind of "hills" are we talking about. If you go down one of these "hills" do you fill the battery using just the regenerating breaking, or can you get down these hills with out that? The B is for steep long hills. I have used B only two or three times coming over the Rockies, or the Cascades.

 

once again, with feeling:
http://techno-fandom.org/~hobbit/cars/b-mode.html
.
_H*

 

No offense intended, but is this really fact or lore?

My brakes aren't broken in yet and grind a little (brand new), I'd swear I can feel them engaging at any speed. Clearly the car is doing regen, but I think it must also be putting pad to disk (or drum). No question in my mind: at about 5 mph it feels like there is a subtle change in the drag and the generator cuts out and brakes are 100% of the stopping power.

 

<div class='quotetop'>QUOTE(benighted @ Apr 30 2006, 08:47 PM) [snapback]247701[/snapback]</div>

Why would I want to switch to B from D (and later back to D) when I can brake w/ greater efficiency and safety (I'm postulating here that both not switching gears and allowing my brake signal to illuminate is safer)?

 

If you're driving down a mountain where you would normally down-shift in another car, then use the B mode. Otherwise, don't.

 

<div class='quotetop'>QUOTE(pocketpenguin @ Apr 30 2006, 08:45 PM) [snapback]247767[/snapback]</div>

pocketpenguin, we are in the minority here driving pre-2004 Prius, so perhaps a bit more explanation is in order. The classic Prius will engage friction brakes as soon as the pedal in the middle is depressed, whether the shifter is "D" or "B". The newer model is a bit more clever at regeneration, and there are many braking situations where those friction brakes are not deployed. Hobbit's fine explanation says essentially the same thing, but clearly it is written from the perspective of a new model Prius driver.

I understand that you drive a 2002 Prius and that your brakes are not yet broken in? Have some components been replaced? Perhaps this is a discussion that should be taken elsewhere, so that B mode can be settled here, once and for all (again).

 

Nope, I'm in a 2006 with 1100 miles on it. So, no they aren't broken in yet.
After reading the article in the link above, I can say that I've felt the release of regen at < 10 mph. I still think I can hear the brakes above that though. Maybe it's the regen "motor" whining, not the brakes. Hard to tell. Oh well, the car stops and with all the coasting I do now the brakes will probably last forever anyway.

 

<div class='quotetop'>QUOTE(pocketpenguin @ May 1 2006, 07:38 PM) [snapback]248331[/snapback]</div>

You might change your profile to show a 2006 rather than a 2002.

 

One way to stay away from full SOC, and to continue using regen braking is to squander electricity. I did this coming down Mt. Washington. It was a warm day, knowing that the battery would max out pretty quick (it did) I tried to figure out how to defeat the car. OK, put the A/C to max cool and roll down all the windows. Basically I descended Mt. Washington on the A/C, without using brake pads and with very little "B" mode. The battery showed full the entire time, but engine braking never came on unless I wanted it.

Why? I just like having all my options available, especially on that hill and grade. There was no chance of storing all of the energy anyway.

 

My $0.02 worth...
I also hear a subtle brake "whine" when applying the brake at speeds over 15-20 mph. I assume this is coming from the generator during regen. Thanks to other PC'ers I've learned that friction braking takes over at +/-8 mph. Now that I'm expecting it, I can detect the subtle shift from regen to friction braking. Another easy test is to touch the brake disc (rotor) immediately after a long drive. Is it cool to the touch? Friction = heat. No heat no friction braking.
Thanks to this thread, and others, I've also stopped leaning on the "B" button. Seems pointless in most situations.
Something else I've noticed, while watching the Consumption screen, is that pressing the brake firmly saves energy! When driving cars with inferior technology (ice always running, even when stopped) I often allow engine power to help hold the car still when stopped on an uphill, applying just as much brake (or throttle) to hold the car still. If I do this in the Prius while stopped on an incline, I can see electric power going to the wheels. This battery drain will immediately stop however, when the brake is firmly applied.
Oh, did I say I love this car?