This would be a question for anyone with a NAV.

While driving into work this morning I took the back roads which has about 5 stop lights. While at one I became curious about current flow when stopped and in EV. Here are my observations:

1. There seems to be no noticeable difference when shifting between N and D. With only have the needle guage that may not be true.
2. Let up on the brake a bit (still have the brake lights on) and there is forward movement. Brake light switch is not monitored to cut off current.

Is there current flow to the drive motor when stopped and your foot on the brake?

-R

 

The NAV certainly doesn't show any current flow, I can tell you that. There still could be some, however I don't believe so... its so easy to just have the controller cut the current with the pedal depressed, especially since the brakes are electrically controlled.

There is at least some difference between N and D. First if you are at an intersection in N the car is NOT going to creep forward. There also appears to be less drag when going down an incline.

 

If the ICE is running when you stop the only way you can remain stationary is for the CVT motor to turn in a direction opposite THE ice and three times faster.

 

Hmmm....It looked like he was only asking about when he was in EV mode, so I wasn't considering the ICE being on.

 

Its important to note that since the brake controls are entirely electronic, there must be an electronic encoded signal for brake pedal position, so the brake light switch isn't the only indicator that can be used for determining if you've lifted your foot....

In fact there might not even be a brake light switch to turn on the lamps...you could just use the position of the pedal to turn the lights on, however I suspect they went with the simple tried and true brake light switch for that function.

 

TeeSter:

You are correct that I was asking while in EV mode.

I respectfully disagree that the brake controls are entirely electronic. While some braking force is via the electronics and is controlled that way the "backup" is mechanical/hydraulics. There would be way to much liability to rely 100% on electronics. The technology isn't to that level yet.

I'm just curious if the ecvt motor is powered while stopped (in EV mode) and the brakes are 100% engaged. Seems like a waste of energy or is it so small that the effort to keep it from being wasted is huge?

-R

 

They engineered into the hybrid to make it seem "normal". Part of that, is idle creep.

With a regular vehicles, with a gas-only engine and an automatic transmission, the vehicle will creep forward as you release the brake pedal, and not yet touched the gas pedal. The hybrid attempts to simulate that. When you partially release the brake, it will sense that, and turn 'on' the electric motor to allow the hybrid to creep forward.

 

Yep. The computer measures how much you are pressing down on the brake pedal. That is how it does it's "requested deceleration" vs. "actual deceleration" calculation, from which it then uses to decide to use regeneration or friction braking (or some combination).

 

If you think about that it makes it very difficult to determine when to cut off the regenerative braking and when to start the actual physical braking. SOMEWHERE there has to be a sensor... ie you could have a physical linkage to the brake pads (but posts seem to say there is not), but somewhere the controller has to know how far that pedal is down in order to give you different levels of regen.

Also.... unfortuantely the NAV doesn't seems to be accurate enough to answer your orginal question. I have the NAV and even when I'm crawling forward as you describe no current arrow appears to the motor. Clearly some current is flowing because the designers wanted to emulate the "idle creep" of a normal automatic, but its not enough for the NAV to register.

 

I haven't found anywhere to confirm this (yet), but I believe there is a direct connection to the rear brakes. Only the fronts are controlled by the computer for regenerative vs. friction braking. So, if the very worse happens, one should still have the rear brakes to (eventually) stop you.

This might also be why the hybrids are the reverse of gas-only vehicles, in that hybrids wear out rear brakes faster than their fronts.