I have unsuccessfully searched high and low for a posting on this, suspecting I'm asking a question answered long ago. I live in the mountains northwest of Denver, and commute 26 miles horizontally and about half a mile vertically down to the plains each day. My half mile drop takes about four miles, and I am under the impression that I can regeneratively brake to my heart's content if I use only very light pedel pressure. My questions are: Does anyone have a black box that can verify that continuous light braking entails NO friction braking? And, how hard do you have to push before friction braking kicks in? I'm thinking it's a pretty good mash before friction braking commences - true? I know all about the engine braking feature, and find it's pretty lame (I still have to brake a lot on my hill). Oh yeah, I'm averaging 47 MPG in my '05 (pkg 6) ) What a magnificent car! I'm running Bridgestone Blizzak Revo 1s as we get a few 'three footers' every winter but I think they'll be fine. I've already had some very positive experiences with them on light ice and a few inches of snow. Regards, Glassguy
How gutsy are you?? I've got a link to show you how to hook up a brake indicator. Coastaletech.com has been advertising one for about 2 years now but is yet to put one into production for sale. But I'll tell you this, I can just about promise you you're not getting close to your friction brakes with the kind of 'riding' you're doing and you are, indeed, regenerating away. My only "but" I'll put on this is that if you hit any significant bumps that can trigger the regen braking to kick off except for the tiny amount of regen you get from 'coasting'. You can get full regen by going into B mode, or you can accelerate just a little bit (by actually pressing the accelerator, not just speeding up thanks to gravity) and it will restore full regen braking ability.
if you get the battery to full green no amount of regen is possible. On a 2500' decent your probably almost always into the full green. Then B is your only practical means of keeping the car at speed. Once full your into friction braking and you have no choice. Here in B.C. we have lots of 3-5000' decents and you can see full lots of time.
As long as you are slightly to moderately applying the brakes you should be using the motors. If you sudden jump on the brakes then you'll be using the disc/drum brakes. Also, at speeds below 8 mph the disc brakes do all the work. Frank and Evan does that sound about right to you? It must be great watching the cumsumption screen on the way into Denver down I-70. I've yet to drive into the mountains in mine. I assume that it's pretty unpleasent watching the comsumption screen on your way home. Are you up near Idaho Springs?
I can't find it, but I remember that they tested and after 100,000 miles there is virtually NO pad wear!.... you have to really bear down to even start friction braking from what I remember!
I'm mixed on what exactly B mode does?... I"ve heard the ICE uses compression to slow the car.. some have said it has NO regen qualities, others have said it does? I myself have wondered that if it does, do both the 10Kw "and" the 50Kw chargers come into play at once?... if so what happens after the battery is fully charged... compression braking?
Windstrings. check out this older thread: http://priuschat.com/index.php?showtopic=1...=30%20amp&st=20 it pretty much lays it all out in gory detail.
one picture is here: http://privatenrg.com/#100kBrakePads of a 2004 Prius. My 2001 Prius has but 81k miles, but the brake pads look about the same. Andrew Grant, Vancouver BC Prius taxi driver, did replace pads a few times (and rear shoes once I recall) on the way to 300k kilometers.
And, the pictures at http://privatenrg.com/#100kBrakePads really do tell it all! You guys are great! Thanks for all the input. efusco: Indeed I do feel the brakes 'grab' upon hitting bumps or taking sharp turns at low (<25) speeds. I had no idea how extensive the range of Regen braking was though! Hudon on the Sunshine Coast (one of our fav vacation spots!): My battery's pretty low when I get home, so I'm not running in the green until about the bottom of the hill the next day, and by then I don't have to brake much. tripp: I'm half-way between Loveland and Estes Pk, and I avg ~16 MPG going up the hill (which IMHO is pretty darned good!). BTW I have lately developed the habit of frequently resetting the MPG calculator, like when I get back to my garage, or whenever the heck I feel like it. If I was cruising some place like the rolling sand hills of western Nebraska I'd probably reset it there to more accurately measure performance with those specific conditions. Richard: The B feature is OK for hills, but not mountains. I find that I have to brake in all the same places (but just not so hard) with and without engine compressive braking. It's really too subtle to be of any use to me. tochatihu: I'm not suprised that a Vancouver cabbie had to replace brakes! Especially if it's all friction braking <8mph. When we were last in BC we stayed at a B&B perched on a VERY steep hillside in N Vancouver with a postcard view of the Lions Gate Bridge. The view is great, but the DRIVE down to the shoreline is a nightmare - lots of cross-traffic and constant braking for about 2 miles. Vancouver must eat brakes! Again, thanks to all for answering my question! Glassguy
I wonder . . . I took my Prius up and down Old Priest Grade on Highway 120. Old Priest Grade is a 1500 foot elevation change in 2 miles - for an average grade of 14+%. There are a couple of steep sections bordering on 20%. Going up was no problem for the Prius with three adults, a nearly full tank, and provisions for a day trip to Yosemite. Coming down was another story! The Prius made it just fine, and felt very safe and in control . . . but when I got to the bottom, there was the distinct odor of hot brakes and the wheels were warm to the touch (it was a cool day . . . snowed in Yosemite). I was in “B†mode and stayed above 8mph 99% of the time . . . but yes, I was using the mechanical brakes. http://www.pashnit.com/roads/cal/OldPriestGrade.htm V.R. of Old Priest Grade. The road you see above on the other mountain is the “easy†highway 120 way to the top. http://virtualguidebooks.com/CentralCalif/...stGrade_FS.html
Quite interesting I was down that grade just once and my brakes were hot, even using engine braking on a conventional car. I am not surprised. I would expect you were all green at the end of the grade.
OK, I did some empirical testing and here are my results: My downhill trip drops from 6800' to 5500' in 3 miles. With an outside temp of about 15 F and traveling in D while VERY LIGHTLY riding the brakes much of the way, upon reaching the bottom of the hill I touched a front disc and nearly burned myself. I work with high temps and estimate the temp to have been 200 C or higher. The next day, with similar conditions but descending in B and with as little braking as possible (just a couple of light taps) the disc was barely warm to the touch when I got to the bottom. My conclusion is that light braking does in fact engage friction braking. I now routinely use B during my descent, even though I have to occassionally accelerate using the ICE in the few places where the road begins to level-out. I know, I know... This is completely contrary to what has been written on this thread, but I encourage anyone who lives adjacent to a big hill to do their own testing to see for themself. One final observation - when descending in B I find that I'm about 2/3 down the hill when there's two green bars left to fill (my battery is pretty drained after climbing home in the evening) and suddenly there's a dramatic change in the ICE sound. It changes from a quiet purr to a rather pronounced engine braking "BRRRRrrrrrrrr..." This typically happens on a pretty steep spot and the increased braking effect is noticable. So, I'm under the impression that there is considerable regenerative braking in B until the battery is nearly full, at which time compressive braking kicks in. Regards, Glassguy
I think that if you're in D once the battery is green you're gonna switch over to disc brakes because otherwise you'd overcharge the battery. B doesn't chage the battery as efficiently as D but in your case, coming down I-70, that's really a non-issue. I'll remember that when I head up into and back down from the Rockies. Save the brakes quite a bit I bet. Thanks for the heads up.
The good Doctor appears to have held back on telling you about - http://techno-fandom.org/~hobbit/cars/imeter/ - http://techno-fandom.org/~hobbit/cars/bp/ the combination of which instrumentation tells me about everything I need to know about regeneration limits and when I'm heating up the brake rotors or not. Regenerative current is limited to 100 amps, which at highway speeds is rather easy to hit with relatively light brake pedal pressure. On big descents, which I got to play with a lot a week ago in the backwoods of Virginia and Kentucky, I try to limit the current to 50A and juggle D and B to soak up the remaining stopping energy in a sensible way -- there's no way I could capture it all into a measly 600 WH battery pack, so I sort of go back to the thinking I would have had with a manual transmission car and match what gear I'd be in to the slope at the time and what terrain is coming up next. . Brake rotor temperature isn't necessarily a good indicator of how much energy was lost in the preceding minutes -- rotors can heat up *astoundingly* fast, so all that heat you burned yourself on may have happened within the last hundred yards or so. . _H*
- Wholly Molely.... I hope your science teacher gave you a nice fat A for that one! I've don't know near as much as you guys about this, but just a question? Is it possible that when we apply the brake regen takes place.... "yes we all know that" BUT is it also possible that once regen is already activated while in B mode that when the brakes are "then"applied, the merely are used for friction? Maybe it doesn't switch over and just lets B mode take priority for regen? anybody know?
