Can you use the B mode too much?

actually that "stalled" current is really minimal... only a couple
of amps. If it was any more than that the car wouldn't creep
forward, it would LEAP forward...
.
_H*

 

<div class='quotetop'>QUOTE(burritos @ Apr 30 2006, 10:36 PM) [snapback]247815[/snapback]</div>

I would be interested in answer to this question as well....



Somewhat related to this thread, I have a daily 1 mile/(300 foot elevation loss) downhill. I am starting to convince myself that gentle braking (to keep speed at about 25 MPH, the speed limit) from the start of the hill results in better battery charging vs. waiting until the bottom of the hill to brake.

This is counter to the way I was taught to drive (don't ride the brakes)...1) is there a problem with prolonged gentle braking on Prius?

One more question....how do you know if you are panic braking? Is this brake petal fully depressed?

 

<div class='quotetop'>QUOTE(jimgraffam @ Apr 30 2006, 08:46 PM) [snapback]247768[/snapback]</div>

I don't know. Preferance? Some people shift from first then to second , third and forth just to switch back to first again after a stop. Someone had noted before that using "B" under 20MPH increases regen efficiency, I was just stating that here.

 

<div class='quotetop'>QUOTE(j24816 @ May 2 2006, 08:26 AM) [snapback]248473[/snapback]</div>

Answers to questions:

1) Why do you not want to refill the battery too soon? Once the traction battery is charged, the Prius has no option for braking other than to use the normal friction brakes, just like a normal car. The B position adds engine drag for extra braking. You are still wasting energy, but it is easier on the friction brakes. Use B on long, steep downhills; the same sort of situation where you see the "Trucks use lower gear" signs.

2) Gentle braking from the start of a hill does result in better regen. Non-panic braking on the Prius is done by the electric motors/generators turning energy into electricity. Hard braking at the end of the hill may exceed their capacity and will also result in more energy lost to heating of the battery. Riding the brakes does not hurt a Prius as the mechanical brakes are not engaged, just the generators.

Not braking at all is even more efficient, as only about 40% of the energy is recaptured and used by regen braking. Just lifting your foot off of the accelerator causes some regen braking. The Prius does this to simulate the engine drag found on a normal car. If you want to coast down a hill, keep the accelerator pedal slightly depressed. You can see this work by watching the info screen on the MFD (just don't drive off the road while watching!)

3) Panic braking is detected by an electrical sensor on the brake pedal. Pedal pressure is sensed by a hydraulic sensor, but a pot attached to the pedal determines the speed of pedal application. If you smash it down, it figures you are panic stopping.

Tom

 

<div class='quotetop'>QUOTE(Presto @ Apr 30 2006, 05:39 PM) [snapback]247699[/snapback]</div>

:blink: I lost my brakes going downhill once, in one of my Honda Civics. Fortunately I was able to stop (emergency brake) before anything bad happened. Now, I haven't recently had the need to use it (B mode - only used it once...to see what it would do), but I greatly appreciate it that it is there! (I did have to have the disc brakes turned on the Civic, though...they warped. Were never the same.)

 

<div class='quotetop'>QUOTE(seasalsa @ Apr 30 2006, 09:29 PM) [snapback]247720[/snapback]</div>

Unless the SOC is too high, then the Prius cannot use regen braking, since there is no place for the charge.

Tom

 

I tried it today going down some really steep hills. not much help.
find it better if I am coming up to a light on level grade where I know I have to stop. Then shift back to D when stopped.

 

Seriously... I've still yet to see a reasonable use for engaging B.
1) If under 9mph... why bother -- you're braking anyways. That pedal in the middle does just fine.
2) If over 10mph and under full SOC, regen braking recovers more energy and requires no action besides pressing that little pedal in the middle.
3) If over 10mph and at full SOC, the Prius is smart enough to use engine braking anyways. No additional action required.

What am I missing?

 

If you exceed 100A into the battery during regen, the physical
brakes *will* come in to help. This is very easy to do at high
speeds, like when you come to the back of one of those "traffic
waves" on the highway and you haven't anticipated it well enough.
The battery can suck it up just so fast, and no faster.
.
_H*

 

<div class='quotetop'>QUOTE(jmccord @ May 1 2006, 10:24 PM) [snapback]248388[/snapback]</div>

The "whine" you hear is the inverter/converter recharging the battery.

 

On our trip down to Disney World we went down some 6% grades. I figured this would be a ligit use for the B Gear. Well after a bit the engine started to really sound like it was revving up past light speed. It did not "sound" right to me so I disengaged it. Any thoughts? Does it normally sound different in B mode? I had almost thought the engine was going into over drive or exceeding the maximum revs. Would like to get some feed back before going back home.

Thanks

 

bump


anyone have any thoughts on my previous question?

 

It shouldn't rev any faster than 5000 rpm, but that does sound like
it's about to explode. Gotta pump a lot of air against the throttle
flap to dissipate all that energy, though...
.
_H*

 

My apologies for doing the "thread from the dead" thing; I'm just trying to learn as much as I can about my newly adopted car.

Having reviewed all the posts in this thread, is it fair to conclude that for those of us who live in relatively flat territory, the "B" position is essentially superflous? The highest elevation in the entire state of FL is something slightly over 300 feet. I work in New Orleans, and drive to and from Pensacola on a weekly basis. The highest elevation on that drive is one rise at 200 ft MSL, most of the rest is well under 50 ft MSL. In New Orleans, the land is flat (except where it's below sea level, as we all now know ). The CCC bridge (main connection from the Westbank to the Eastbank) peaks at less than 200 ft, and on the three glides I've done down the back side, my SOC goes to the top blue bar or first green -- no full SOC for me yet. Again, would I ever need to bother with "B"? Thanks for any feedback.

 

<div class='quotetop'>QUOTE(efusco @ Aug 2 2006, 06:19 AM) [snapback]296240[/snapback]</div>

We live in CA, and just came back from a trip to the "Gold" country about 1500 feet above our home, and the trip also required crossing the Altamont pass. I used the B position on these long downgrades, and I believe that it worked quite well. It kept me from speeding down the grade, and I used very little of the "pedal" brake. By the way, the CONSUMPTION meter on these downgrades showed 100 mpg or more for its full 30 minute time - so I really appreciate its performance. I went to this forum to see if I was using it correctly (Toyota is so helpful ). Thanks to posters - I am much better informed.

PS - We absolutely love our now almost 1 year old Prius - Not only is it "green", it's quality, comfort, space, and ease of driving exceed any car we have ever had (well, OK, the fun factor doesn't quite equal the Porsche or Mustang we once had).

 

<div class='quotetop'>QUOTE(hobbit @ Apr 30 2006, 10:24 PM) [snapback]247742[/snapback]</div>

:lol: :lol: Dang Hobbit!, I was just in the middle of a Sunday morning sip of coffee in front of the fire when I read your post and started laughing so hard I almost had coffee coming out of my nose.......

Moral of this post: its better to be fully awake when you read PriusChat!!! B)