So, when I'm just rolling along, without my foot on the gas or brake, is the car braking when it's coasting? That's weird! My daddy always taught me not to ride the brakes...

 

elsifer — Yes, it applies a small retarding force when you "coast," thereby simulating the same kind of deceleration that you get in a non-hybrid when you take your foot off the accelerator. They didn't have to choose to do this, but I guess they wanted the hybrid to drive like a "normal" car in most respects. This retarding force, which causes the deceleration, is provided by MG2 recovering some kinetic energy into electricity — i.e., by regeneration. Look at the energy flow display, and you'll see an arrow from the wheels to the battery when you coast. You're certainly not "riding the (friction) brakes," so your daddy should be happy!

Stan

 

Stan

If I read your explanation correctly, the physical brakes (is this what you called "friction" brakes--rotors, pads, etc) are only activated when the car is almost at a complete stop or during hard braking, and regenerative braking is done via the MG2 motor generators.

Are the physical brakes activated when I apply the brake pedal at higher speeds?

Does this imply that the brake components will have a longer life since they're not used as much as in a "normal" car?

Thanks

 

IMPO, I think the friction brakes on the front wheels are not used except when nearly stopped, or you want to stop faster than the MG2 can produce a charge (heavy braking), but the rear brakes are used more often that the front. I think the rears come on to balance out the stopping force the MG2 is applying. I am not sure, but I base this opion on the fact that my rear rotors seem to be getting more wear than the fron ones. It is not uncommon for the front rotors to still have rust on them afetr a couple drives, but the rear rotors are nice and shinny like that have been used. I will be keeping a closer eye on the rear pads than the front ones, as expect the front pads to last a long time.

 

klynch — One can stop a car with friction brakes faster than one can accelerate it up to speed under ICE power. MG2 can only handle a certain maximum power flow, and this isn't adequate to brake the car rapidly regeneratively if the brake pedal is pressed hard. If your braking demand exceeds the system's regenerative capability, the friction brakes are brought into play at speed, dumping kinetic energy as heat. If you don't demand such hard braking, the regenerative system can recover much of the kinetic energy electrically. The "whine" from MG2 when braking regeneratively is louder than when accelerating because of the greater power passing through MG2 when braking moderately hard. I don't know the front/rear braking proportioning used. If there is always some braking on the rear wheels, for stability reasons, then this component of the energy is being wasted in friction. This would agree with what ag4ever says. Yes, under moderate braking, I would expect the front brake pads (and perhaps the rears too) to last "forever."

Stan

 

Thanks Stan.

 

It definately does appear that the rear brakes are working more than the front. I have noticed every time I wash the car the rear wheels have quite a bit of brake dust on them as would a normal front brake would have and the front wheels are barely dusty.

One of our members has about 18000 miles logged and would be a good candidate for a brake check. Anybody with over ten thousand miles have their wheels rotated and pads checked yet?

 

I will soon, I have over 6000 miles on it since the middle of October.

On a brighter side, we just moved and my commute to work is now 20 miles less which translates into one gallon of fuel a day in savings. Yee Haw.