Curious about current flow while stopped
#11
Re: Curious about current flow while stopped
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:
-R
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:
- There seems to be no noticeable difference when shifting between N and D. With only have the needle guage that may not be true.
- 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.
-R
The reason you roll back when you release the brake pedal while stopped on an incline for a bit is because it takes a second for the creep mode to sense the reverse movement and adds more power to the traction motor.
If you folks need more info, I'll see if I could find the "Creep Mode" patent again.
GaryG
Last edited by GaryG; 04-09-2007 at 04:58 PM.
#12
Re: Curious about current flow while stopped
I been meaning to post about the "Creep Mode" for a while now and warn you creeper to stop it. If you hold the brake and don't allow any creeping, you save energy. The program works with the ABS system and when you let it creep, you begin sending current to the drive motor. If you hold the brake pedal for no vehicle movement, no current is used or activated to the drive motor or Traction motor as it's called.
The reason you roll back when you release the brake pedal while stopped on an incline for a bit is because it takes a second for the creep mode to sense the reverse movement and adds more power to the traction motor.
If you folks need more info, I'll see if I could find the "Creep Mode" patent again.
GaryG
The reason you roll back when you release the brake pedal while stopped on an incline for a bit is because it takes a second for the creep mode to sense the reverse movement and adds more power to the traction motor.
If you folks need more info, I'll see if I could find the "Creep Mode" patent again.
GaryG
Cheers,
rcomeau
#13
Re: Curious about current flow while stopped
The creep also is a safety feature. It it were not there, soon, especially if this were your only car, you would get used to the zero creep, and fall into a habit of NOT applying the brake at stoplights, etc. This would lead to many accidents as the car would roll down a slight hill not perceived by the driver, or even the wind could push you while you were looking down and you'd not notice till you hit something.
I remember Ford engineers saying that they wanted to both simulate a traditional automatic, as well as force people to apply the brake at stops.
I notice on some radio stations I get an electrical "whine" over the speakers... only when I'm standing still, only in EV, and only with my foot on the brake. Anyone else notice this? Even at 1mph the noise immediatly goes away. ???
-John
I remember Ford engineers saying that they wanted to both simulate a traditional automatic, as well as force people to apply the brake at stops.
I notice on some radio stations I get an electrical "whine" over the speakers... only when I'm standing still, only in EV, and only with my foot on the brake. Anyone else notice this? Even at 1mph the noise immediatly goes away. ???
-John
#14
Re: Curious about current flow while stopped
I've never heard that myself... is it only on AM?
#15
Re: Curious about current flow while stopped
~John
#16
Re: Curious about current flow while stopped
when shifting between N and D. With only have the needle guage that may not be true.
-R
- 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.
-R
Current is still flowing. The creep with the BOO switch on is designed to simulate the torque converter creep on a conventional automatic trans.
#17
Re: Curious about current flow while stopped
It wouldn't make sense to waste battery energy by torquing MG2 when the car is stationary with its brakes applied sufficiently firmly that it won't move. Certainly, in the TCH, there's no energy flow to MG2 in this condition. The interesting question is how the designers know when they don't need to send power to MG2. The answer, in the Toyota hybrids, is to use an additional "stroke simulator" hydraulic cylinder. It provides the normal brake pedal "resistance" that lets the driver feel how much force he/she is applying. The car then decides, based on this force amount, how best to apportion the total force between the regenerative braking (via MG2) and the friction braking. Regenerative braking stops when the car is almost stationary, and then only friction braking is used to stop and hold the car. If the driver then eases up on the brake pedal somewhat, this is sensed and power is sent to MG2 (and so indicated on the power-flow display) to cause the car to start to creep. I'd guess that the FEH probably does something similar.
Stan
Stan
#18
Re: Curious about current flow while stopped
The creep also is a safety feature. It it were not there, soon, especially if this were your only car, you would get used to the zero creep, and fall into a habit of NOT applying the brake at stoplights, etc. This would lead to many accidents as the car would roll down a slight hill not perceived by the driver, or even the wind could push you while you were looking down and you'd not notice till you hit something.
I remember Ford engineers saying that they wanted to both simulate a traditional automatic, as well as force people to apply the brake at stops.
I remember Ford engineers saying that they wanted to both simulate a traditional automatic, as well as force people to apply the brake at stops.
I always thought the creep was a side-effect of the automatic transmission that was not intended by the inventors, but tolerated and now has become expected. Kind of like how some blind groups are asking that hybrids and electrics be fitted with noise makers so they can hear us coming.
Anyways, my 2¢ worth.
Cheers,
rcomeau
#19
Re: Curious about current flow while stopped
It wouldn't make sense to waste battery energy by torquing MG2 when the car is stationary with its brakes applied sufficiently firmly that it won't move. Certainly, in the TCH, there's no energy flow to MG2 in this condition. The interesting question is how the designers know when they don't need to send power to MG2. The answer, in the Toyota hybrids, is to use an additional "stroke simulator" hydraulic cylinder. It provides the normal brake pedal "resistance" that lets the driver feel how much force he/she is applying. The car then decides, based on this force amount, how best to apportion the total force between the regenerative braking (via MG2) and the friction braking. Regenerative braking stops when the car is almost stationary, and then only friction braking is used to stop and hold the car. If the driver then eases up on the brake pedal somewhat, this is sensed and power is sent to MG2 (and so indicated on the power-flow display) to cause the car to start to creep. I'd guess that the FEH probably does something similar.
Stan
Stan
The people lurking this site need to join and ask me questions about my MTE and how to save gas. Choose and pick my methods, but you can save at the pump.
GaryG
#20
Re: Curious about current flow while stopped
I'm sure you're right about this. I think what John was saying was that people who are accustomed to driving automatics need for these vehicles to behave like automatics or there could be trouble.