Is there a way to tell, when I am moving and stepping on the brake pedal, whether the car is charging the battery or using the brake pads. I assume that with mild brake pedal pressure, power regeneration is on. I also assume that if I press real hard, the brake pads will act in concert with power regeneration. When is the crossover between the two points? Is there a way to tell. Thanks
Even with mild braking there is a transition from regenerative to friction braking at 7 mph (regen stops at the lowest speeds.) When I first picked up the car and was driving home I had to brake moderately to a stop in some low speed stop and go on a freeway. The braking transition plus the infant transition brakes (not yet bedded in) resulted in a brief feeling of having zero brakes and I ended up far closer to the car in front than I wanted to be. I don't know how to detect the transition at higher speeds on the road now. I imagine the vast majority of my braking uses regen only. You could however test the feel of regen vs. friction brakes by braking in neutral. When you brake in neutral all of it will be coming from the friction pads.
Hi Rhino, this has been asked and I don't believe there is a method to definitively tell when it transitions from regen to friction braking. I can feel it at 7 mph when it changes but I cannot feel it if I progressively press harder at higher speeds. I believe it switches to friction without a lot of brake pressure. I brake lighter and earlier in my Prius than I used to to attempt to stay in regen braking.
You would probably need to use Scangauge and watch the regeneration current levels. Without instrumentation, there is no indication other than the seat of your pants. Tom
Depends on the model - my 2010 shows arrows going to the battery when the regenarative braking is on. The arrows stop flowing when the friction brakes kick in (somewhere between 7 -10 mph).
This shows when regeneration stops, but not necessarily when friction braking starts. At higher braking levels, regenerative braking and friction braking can occur simultaneously. Tom
Tom, Thank you. I have the Scanguage II on order from the company associated with PriusChat today. Which guage shows the regeneration current levels? Thank you everybody. I am looking forward to the fun.
ScanGuage listens in on the CAN bus, which is where all of the control messages route back and forth. You can program your ScanGauge to display various items from those that are available. I can't give you the exact setup, but the instructions should show you how. If not, post a specific question and one of the ScanGauge gurus can help. Tom
On the Scanguage II BTA which is battery current will show the current into and out of the battery. You can see the current jump when you are regenerating. On my 2008 I see anywhere from 15 to 90 Amps depending how hard I'm pushing the brakes and how fast I'm going. BTA is an x guage as mentioned in the Scanguage manual. There are many measurements available to manually program as x guages. I'm not sure how you tell when the friction brakes are being applied in conjunction with the regeneration during a quick stop during which friction and regeneration are both at work. As was mentioned before at <8MPH the braking is all friction as there's very little energy left to generate any appreciable power. You will see the current BTA drop instantly when you cross this threshold.
Everyone, Thank you. I'll set up the scanguage to read RPM, coolant temp, High Voltage Battery current. Haven't figured out how to use the 4th guage yet. I'll worry about it when the time comes. Thank you.
On the 3rd Gen, it's much harder to tell. Toyota has done a wonderful job making that transition smooth. However, for those of us who want to know, it's easier on the Gen 2.
I looked at this as we now have the SGII XGauge for AMPs and am surprised at what I am seeing. Regen braking appears to be occurring even after braking significantly harder after the CHG bar is filled. This is taking into account the fact that the SGII display is not real time as I believe I braked long enough to allow the SGII to update. It never returned to anything positive or near zero. It stayed around 80-90 even after braking harder beyond filling the CHG bar. Is it possible that regen brakes continue to be engaged along with friction brakes when braking hard? Unscientific observations of the SGII AMPs appears to indicate this. What have others observed regarding this? On a related note, I've seen as high as around 95 AMPs from regen and as high as 135 AMPs during heavy acceleration, as in pedal to the floor. (I was curious and did it just to see how many AMPs it would pull). Do these numbers seem accurate and reasonable?
Below 8 mph is all friction, or I've taken that from what I've read. Above that, I don't see why they couldn't work together, even though it is discussed as if it suddenly, magically becomes an emergency friction brake stop. Do you see regen AMPs below 8 mph? Not surprised that greater regen vs HSI display is available, since PWR band end way before full throttle. How about displaying MG1 rpm, MG2 rpm, ICE rpm, and amps. If regen vanishes in a quick stop, you would expect some wild fluctuations: amps to ~0, MG2 dropping with speed obviously, MG1 and ICE making up the difference within the PSD such that regen is 0. IOW, can we correlate MG rpms to regen?
Yes. Regenerative braking is limited by the MGs and the HV battery. With heavy non-panic braking the Prius will use both regenerative and friction braking. It makes sense to recover as much energy as possible. Tom
