regenerative deceleration

i worry that giving people more than one option to brake, will cause accidents. the human brain isn't always that quick. i'm happy with keeping it brake pedal only, and improving the efficiency with each generation.

 

I don't think it's just emergency braking - even "normal" braking, say on a downhill slope EXIT ramp from 100 to 60km/hr, you will, in most situations brake harder than just using REGEN braking, thus using some mechanical brake.

Another consideration - if you drove for 2 yrs using just REGEN and then had a Panic Stop - the rust build up on your Disks would rip the brake pads to shreds in one stop.

 

That would require a very high power electrical system and battery, such as that of a Tesla.

For the Gen3 Prius, the regeneration limit was set by the battery at about 27kW. For comparison, emergency braking at highway speed can exceed 500kW.

 

I want nice simple brakes. Press the pedal, stop the car.

If the Prius gets any more complicated, I'm going back to my 1995 Camry!

 

For purposes of testing for brake drag, I've been known to make completely-brakeless stops by using B mode down to about 6 MPH, then shifting to reverse until the car just comes to zero (at which point it's ok to stab the brakes, and won't heat the rotors or mess up the test). It works but it's fiddly; I certainly wouldn't do it in normal driving. (I scope out the place my test will end up in advance.)

One of the good things about the Prius brakes working exactly the way they do is that if anything surprising should happen with traction while you are slowing regeneratively, the car can switch directly to 4-wheel hydraulic ABS so quickly you almost don't notice (though that almost has been the genesis of countless PriusChat threads...).

-Chap

 

I have yet to hear, feel, or see any "regenerative" braking. What am I missing?

But I did notice a weird thing involving my brakes when I was driving around in PWR mode for 5 months. Many times, the brakes would feel very mushy, weak, and I had to push the pedal further down to slow the car. Now that I switched back to ECO mode, the brakes feel good and strong.

Just another Prius Oddity...

 

Whenever the Hybrid System Indicator is down below the ZERO level, in the CHG area, it's doing regenerative braking and charging the battery.


Alternatively, if you have the Energy Monitor displayed you'll see power coming from wheels to battery - that's regenerative braking.

 

Thanks. Understood. Why don't they just call it "battery charging." It's not really braking as we know it; it's not something I can feel in the brake pedal... or is it?

I still get grabby brakes often. And I've had mushy brakes. Will they ever feel normal??? This Prius sure is a strange car.

 

Not initially - on level ground, you could be driving at 110km/hr and take your foot off the throttle and it would slow down - you would see the Monitor or Indicator showing charge - it would be slowing down quicker than - say a Petrol Corolla - in neutral. My understanding - if you brake with the pedal enough for the Hybrid System Indicator "CHG" zone to be almost full (blue):
-
it is only using regenerative braking. Should the window be COMPLETELY blue, you could be then using some mechanical brakes.

NORMAL - I don't think there is such a thing. My Fiesta and Focus had similar brake feel, my Dad's Camry needed considerably more force to brake and didn't feel as progressive. But he thought his was NORMAL - I didn't - partly what you get used to. I remember the first Mercedes ('60s) I drove, the accelerator needed to be planted so deep to get acceleration if felt quite odd - I far preferred my Corolla and VW.

STRANGE - yeah maybe - I've often bought cars a little left-field - and PRIUS is a little different.

 

I find it to be strange, weird, odd... but in a fun kind of way. I never know what to expect from day to day.

But the most odd thing is the grabby brakes. Just a light, easy, gentle push on the brake pedal..... and then GRAB!!! I better not have coffee in my hand.

 

probably first year new generation blues. in time, toyota will come out with a recall or tsb. until then, dealers will have no clue.

 

Bisco's up early this morning.,.

 

Afaik it would need a rectifier to convert AC to DC

 

It needs a rectifier to convert AC to DC. The inverter converts DC to AC and I don't think either can function in reverse.

 

No ... no, it doesn't. The conversion from DC to AC (and back) is all done by large transistors in switching mode in a bridge configuration (how do you rectify AC with a bridge of switches? Turn these two on for half the waveform, turn those two on for the other half ... how do you invert DC to AC with a bridge of switches? Pretty much the same way), the voltage adaptation between the 200-ish volt battery and the 650-ish volt motors is done by bucking/boosting using inductance and capacitance at the switched pulse edges. The computer driving the precise timing of the switch transitions has complete control of the process, forward and reverse.

This is one of the most studied, discussed, and understood topics in all Priusland ... in addition to the Toyota manuals and course materials (all on techinfo, though you need $15 to play, best starting place is New Car Features Manual), there are lots of technical discussion threads here on PriusChat going back years, all there for the searching.

-Chap

 

The battery is the weakest link of the regeneration path, so the higher 60kW rating of MG2 doesn't help. The full 60kW rating is used only during acceleration when both the ICE and battery are providing power at the same time.

All the high voltage motor-drive / inverter / rectifier stuff is built to run power both ways, as both directions are needed at various different times during normal propulsion operations. Given this, no additional hardware is needed for regenerative braking, just more software.

Unlike the MG driver hardware, the high-voltage to 12V inverter is one-way only.