How good is the regen braking?
#1
06-04-2009, 02:21 PM
How good is the regen braking?
I was just wondering how much the friction brakes are actually used. I can feel them come on in the last few feet of a stop, but do they ever come on earlier? It seems to me that the electric motor wouldn't be able to generate from more power than it can produce in the other direction, which means that since I can't accelerate at all from 35 with only the electric motor, how can even moderate braking be accomplished without the friction brakes at that speed? If that makes sense...
#3
06-04-2009, 05:04 PM
Re: How good is the regen braking?
I was just wondering how much the friction brakes are actually used. I can feel them come on in the last few feet of a stop, but do they ever come on earlier? It seems to me that the electric motor wouldn't be able to generate from more power than it can produce in the other direction, which means that since I can't accelerate at all from 35 with only the electric motor, how can even moderate braking be accomplished without the friction brakes at that speed? If that makes sense...
#4
06-04-2009, 11:37 PM
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Re: How good is the regen braking?
There is a 4 mile stretch of highway where I can watch such things as this. Normally I get 57 mpg or go into the ev mode along though here. If I see the battery is at minimum and the MG kicks in to charge the battery. Then the mpg drops to 47 mph for about a mile till the traction battery charged up.
That's probably lots of charge amps, but only pulls 10 mpg on the engine for a short time.
That's probably lots of charge amps, but only pulls 10 mpg on the engine for a short time.
#5
06-04-2009, 11:43 PM
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Re: How good is the regen braking?
The Regen braking can slow the car rather quickly from 60 mph down to 10mph without it using the friction brakes.
The friction brakes come in around 8 mph, ever time you stop. They also are used some when using the Brake position like on a steep grade. The friction brakes will be engaged in any panic stop.
The friction brakes come in around 8 mph, ever time you stop. They also are used some when using the Brake position like on a steep grade. The friction brakes will be engaged in any panic stop.
Last edited by rburt07; 06-04-2009 at 11:46 PM.
#6
06-05-2009, 10:42 AM
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Re: How good is the regen braking?
I was just wondering how much the friction brakes are actually used. I can feel them come on in the last few feet of a stop, but do they ever come on earlier? It seems to me that the electric motor wouldn't be able to generate from more power than it can produce in the other direction, which means that since I can't accelerate at all from 35 with only the electric motor, how can even moderate braking be accomplished without the friction brakes at that speed? If that makes sense...
Last edited by wwest; 06-05-2009 at 01:27 PM.
#7
06-05-2009, 12:19 PM
Re: How good is the regen braking?
One of the largest misconceptions about the TCH is the regenerative braking system and how it works.
First, the TCH does NOT have separate generators for the braking system. The same electric motor/generators, MG2 and MG1 are used for regenerative braking as are used for propulsion. When the footbrake is lightly applied during the early phase of a stop or deceleration, the ECU exerts command over MG1 to cause two things. First, to reduce ICE RPMs so as to remove torque, and second to cause MG2 to become a generator that is mechanically driven by the cars kenetic energy through the drive train. At the same time, light mechanical braking is applied to the REAR wheels to prevent the car from trying to spin or drift. The exact amount of rear wheel braking depends on driver applied brake pressure, vehicle speed and a few other variables.
As the demand for increased braking is applied by the driver, the regenerative rate on MG2 is stepped up by increasing the generator current ouput, while at the same time the mechanical braking to the rear wheels is increased. The process continues until the generator output reaches its maximum charge rate. At that point all additional applied braking is mechanical to both the front and rear wheels.
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed. At that point, additional mechanical braking is applied and the charge rate is lowered to decrease the generative current demand on MG2. At a very low speed of around 6-8 MPH the regenerative system is shut down by the ECU by removing the charging loop to the battery, and the remaining braking is performed by only the mechanicl brakes.
During this whole time, the cars computers are setting mechanical braking ratios between the front and rear mechanical brakes to ensure that the braking effort does not cause the car to want to switch ends. Since all of the regenerative braking effort is through the front tires, it is importantant that this ratio between regenerative and mechanical braking be retained.
Note that in AWD hybrids, like the Highlander, it is possible to further reduce the need for mechanical braking because the kinetic energy can be recovered through the drive line from all four wheels. I think that future hybrids may incorporate more AWD technologies, either using connected AWD drive lines or in-wheel electric motors to futher reduce the need for mechanical braking and better utilize regenerative concepts.
There is a link that explains some of these ideas here = http://www.hybridsynergydrive.com/en...e_braking.html
RFB
First, the TCH does NOT have separate generators for the braking system. The same electric motor/generators, MG2 and MG1 are used for regenerative braking as are used for propulsion. When the footbrake is lightly applied during the early phase of a stop or deceleration, the ECU exerts command over MG1 to cause two things. First, to reduce ICE RPMs so as to remove torque, and second to cause MG2 to become a generator that is mechanically driven by the cars kenetic energy through the drive train. At the same time, light mechanical braking is applied to the REAR wheels to prevent the car from trying to spin or drift. The exact amount of rear wheel braking depends on driver applied brake pressure, vehicle speed and a few other variables.
As the demand for increased braking is applied by the driver, the regenerative rate on MG2 is stepped up by increasing the generator current ouput, while at the same time the mechanical braking to the rear wheels is increased. The process continues until the generator output reaches its maximum charge rate. At that point all additional applied braking is mechanical to both the front and rear wheels.
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed. At that point, additional mechanical braking is applied and the charge rate is lowered to decrease the generative current demand on MG2. At a very low speed of around 6-8 MPH the regenerative system is shut down by the ECU by removing the charging loop to the battery, and the remaining braking is performed by only the mechanicl brakes.
During this whole time, the cars computers are setting mechanical braking ratios between the front and rear mechanical brakes to ensure that the braking effort does not cause the car to want to switch ends. Since all of the regenerative braking effort is through the front tires, it is importantant that this ratio between regenerative and mechanical braking be retained.
Note that in AWD hybrids, like the Highlander, it is possible to further reduce the need for mechanical braking because the kinetic energy can be recovered through the drive line from all four wheels. I think that future hybrids may incorporate more AWD technologies, either using connected AWD drive lines or in-wheel electric motors to futher reduce the need for mechanical braking and better utilize regenerative concepts.
There is a link that explains some of these ideas here = http://www.hybridsynergydrive.com/en...e_braking.html
RFB
Last edited by FastMover; 06-05-2009 at 12:23 PM.
#8
06-05-2009, 01:22 PM
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Join Date: Sep 2006
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Re: How good is the regen braking?
One of the largest misconceptions about the TCH is the regenerative braking system and how it works.
First, the TCH does NOT have separate generators for the braking system. The same electric motor/generators, MG2 and MG1 are used for regenerative braking as are used for propulsion. When the footbrake is lightly applied during the early phase of a stop or deceleration, the ECU exerts command over MG1 to cause two things. First, to reduce ICE RPMs so as to remove torque, and second to cause MG2 to become a generator that is mechanically driven by the cars kenetic energy through the drive train. At the same time, light mechanical braking is applied to the REAR wheels to prevent the car from trying to spin or drift. The exact amount of rear wheel braking depends on driver applied brake pressure, vehicle speed and a few other variables.
As the demand for increased braking is applied by the driver, the regenerative rate on MG2 is stepped up by increasing the generator current ouput, while at the same time the mechanical braking to the rear wheels is increased. The process continues until the generator output reaches its maximum charge rate.
"...generator output reaches it maximum charge rate..."
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
And if the hybrid battery is already mostly charged..??
At that point all additional applied braking is mechanical to both the front and rear wheels.
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current.
At that point, additional mechanical braking is applied and the charge rate is lowered to decrease the generative current demand on MG2. At a very low speed of around 6-8 MPH the regenerative system is shut down by the ECU by removing the charging loop to the battery, and the remaining braking is performed by only the mechanicl brakes.
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
.
During this whole time, the cars computers are setting mechanical braking ratios between the front and rear mechanical brakes to ensure that the braking effort does not cause the car to want to switch ends. Since all of the regenerative braking effort is through the front tires, it is importantant that this ratio between regenerative and mechanical braking be retained.
And in the case that ABS detects impending wheel lockup due to braking the regen system will be INSTANTLY disengaged.
Note that in AWD hybrids, like the Highlander, it is possible to further reduce the need for mechanical braking because the kinetic energy can be recovered through the drive line from all four wheels. I think that future hybrids may incorporate more AWD technologies, either using connected AWD drive lines or in-wheel electric motors to futher reduce the need for mechanical braking and better utilize regenerative concepts.
There is a link that explains some of these ideas here = http://www.hybridsynergydrive.com/en...e_braking.html
RFB
First, the TCH does NOT have separate generators for the braking system. The same electric motor/generators, MG2 and MG1 are used for regenerative braking as are used for propulsion. When the footbrake is lightly applied during the early phase of a stop or deceleration, the ECU exerts command over MG1 to cause two things. First, to reduce ICE RPMs so as to remove torque, and second to cause MG2 to become a generator that is mechanically driven by the cars kenetic energy through the drive train. At the same time, light mechanical braking is applied to the REAR wheels to prevent the car from trying to spin or drift. The exact amount of rear wheel braking depends on driver applied brake pressure, vehicle speed and a few other variables.
As the demand for increased braking is applied by the driver, the regenerative rate on MG2 is stepped up by increasing the generator current ouput, while at the same time the mechanical braking to the rear wheels is increased. The process continues until the generator output reaches its maximum charge rate.
"...generator output reaches it maximum charge rate..."
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
And if the hybrid battery is already mostly charged..??
At that point all additional applied braking is mechanical to both the front and rear wheels.
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current.
At that point, additional mechanical braking is applied and the charge rate is lowered to decrease the generative current demand on MG2. At a very low speed of around 6-8 MPH the regenerative system is shut down by the ECU by removing the charging loop to the battery, and the remaining braking is performed by only the mechanicl brakes.
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
.
During this whole time, the cars computers are setting mechanical braking ratios between the front and rear mechanical brakes to ensure that the braking effort does not cause the car to want to switch ends. Since all of the regenerative braking effort is through the front tires, it is importantant that this ratio between regenerative and mechanical braking be retained.
And in the case that ABS detects impending wheel lockup due to braking the regen system will be INSTANTLY disengaged.
Note that in AWD hybrids, like the Highlander, it is possible to further reduce the need for mechanical braking because the kinetic energy can be recovered through the drive line from all four wheels. I think that future hybrids may incorporate more AWD technologies, either using connected AWD drive lines or in-wheel electric motors to futher reduce the need for mechanical braking and better utilize regenerative concepts.
There is a link that explains some of these ideas here = http://www.hybridsynergydrive.com/en...e_braking.html
RFB
Last edited by wwest; 06-05-2009 at 01:32 PM.
#9
06-05-2009, 02:27 PM
Re: How good is the regen braking?
"...generator output reaches it maximum charge rate..."
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
Agreed. I should have said maximum permissible charge rate. It would be limited by the battery's ability to accept the charge current (maximum charging voltage or thermal rate limitation) as well as the reverse torque available to the drive system.
And if the hybrid battery is already mostly charged..??
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current."
Written for laymen not electrical types. Your statement is true so far as it goes, but there must be a high enough torque being supplied from the drive train from the remaining kinetic energy. Otherwise the higher current cannot be maintained. (The maximum DC charge current that can be extracted is a function of the RMS of the generated AC and the system has a finite amplitude. This is frequency independent up to a point, but at very low RPM the frequency period becomes too long to sustain the DC ouput at a constant voltage given the maximum design amplitude. These batteries have a very small DC voltage range over which they can accept a charge current without damage, and that limits the charging rate as well.)
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
I did not imply removal of the AC field. I said removing the "charging loop to the battery" That is the DC side. True, the windings will still generate a potential either as a flux (open armature circuit) or as a voltage (closed armature circuit, but with no connection to the DC path as far as the battery, so there is no charge voltage and thus no charge current. The AC from MG2 is utilized in a different manner once the battery charge is removed. (I'll leave it to you to figure that one out. HINT: What happens to MG2 when you are going down an extended downhill grade, the ICE is in fuel cut-off, and the battery reaches the maximum SOC scheduled by the ECU? Kinetic energy is still being applied and the drive train is feeling large amounts of negative torque. MG2 is still producing a field, so where does it go? ANOTHER HINT: The relationship between MG2 and MG1 is more than just mechanical across the PSD.)
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
Agreed. I should have said maximum permissible charge rate. It would be limited by the battery's ability to accept the charge current (maximum charging voltage or thermal rate limitation) as well as the reverse torque available to the drive system.
And if the hybrid battery is already mostly charged..??
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current."
Written for laymen not electrical types. Your statement is true so far as it goes, but there must be a high enough torque being supplied from the drive train from the remaining kinetic energy. Otherwise the higher current cannot be maintained. (The maximum DC charge current that can be extracted is a function of the RMS of the generated AC and the system has a finite amplitude. This is frequency independent up to a point, but at very low RPM the frequency period becomes too long to sustain the DC ouput at a constant voltage given the maximum design amplitude. These batteries have a very small DC voltage range over which they can accept a charge current without damage, and that limits the charging rate as well.)
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
I did not imply removal of the AC field. I said removing the "charging loop to the battery" That is the DC side. True, the windings will still generate a potential either as a flux (open armature circuit) or as a voltage (closed armature circuit, but with no connection to the DC path as far as the battery, so there is no charge voltage and thus no charge current. The AC from MG2 is utilized in a different manner once the battery charge is removed. (I'll leave it to you to figure that one out. HINT: What happens to MG2 when you are going down an extended downhill grade, the ICE is in fuel cut-off, and the battery reaches the maximum SOC scheduled by the ECU? Kinetic energy is still being applied and the drive train is feeling large amounts of negative torque. MG2 is still producing a field, so where does it go? ANOTHER HINT: The relationship between MG2 and MG1 is more than just mechanical across the PSD.)
Last edited by FastMover; 06-05-2009 at 02:30 PM.
#10
06-05-2009, 03:23 PM
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Join Date: Sep 2006
Location: Beautiful Pacific NW
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Re: How good is the regen braking?
"...generator output reaches it maximum charge rate..."
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
Agreed. I should have said maximum permissible charge rate. It would be limited by the battery's ability to accept the charge current (maximum charging voltage or thermal rate limitation) as well as the reverse torque available to the drive system.
And if the hybrid battery is already mostly charged..??
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current."
Written for laymen not electrical types. Your statement is true so far as it goes, but there must be a high enough torque being supplied from the drive train from the remaining kinetic energy. Otherwise the higher current cannot be maintained. (The maximum DC charge current that can be extracted is a function of the RMS of the generated AC and the system has a finite amplitude. This is frequency independent up to a point, but at very low RPM the frequency period becomes too long to sustain the DC ouput at a constant voltage given the maximum design amplitude. These batteries have a very small DC voltage range over which they can accept a charge current without damage, and that limits the charging rate as well.)
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
I did not imply removal of the AC field. I said removing the "charging loop to the battery" That is the DC side. True, the windings will still generate a potential either as a flux (open armature circuit) or as a voltage (closed armature circuit, but with no connection to the DC path as far as the battery,
so there is no charge voltage and thus no charge current.
Sorry, but if you open the stator output of "these" motors while they're still rotating the voltage output will rise as high as need be to find, or open, a current flow path.
The AC from MG2 is utilized in a different manner once the battery charge is removed. (I'll leave it to you to figure that one out. HINT: What happens to MG2 when you are going down an extended downhill grade, the ICE is in fuel cut-off, and the battery reaches the maximum SOC scheduled by the ECU? Kinetic energy is still being applied and the drive train is feeling large amounts of negative torque. MG2 is still producing a field, so where does it go? ANOTHER HINT: The relationship between MG2 and MG1 is more than just mechanical across the PSD.)
I would suspect that the system NEVER uses the generator's maximum charge rate even if the SOC is extremely low....absent a stack of resistors. That would be a serious level of charge to be virtually instantaneously pumping back in the the battery pack, or even the capacitor bank undoubtedly in the hybrid battery regen charging "loop"/path.
Agreed. I should have said maximum permissible charge rate. It would be limited by the battery's ability to accept the charge current (maximum charging voltage or thermal rate limitation) as well as the reverse torque available to the drive system.
And if the hybrid battery is already mostly charged..??
As the car slows the higest charge current used cannot be maintained by MG2 due to insufficient axle speed.
That's just WRONG...!!
Just as the AC motors can supply their HIGHEST level of torque at their lower speeds that same is true in reverse for supplying charge current."
Written for laymen not electrical types. Your statement is true so far as it goes, but there must be a high enough torque being supplied from the drive train from the remaining kinetic energy. Otherwise the higher current cannot be maintained. (The maximum DC charge current that can be extracted is a function of the RMS of the generated AC and the system has a finite amplitude. This is frequency independent up to a point, but at very low RPM the frequency period becomes too long to sustain the DC ouput at a constant voltage given the maximum design amplitude. These batteries have a very small DC voltage range over which they can accept a charge current without damage, and that limits the charging rate as well.)
"...removing the charging loop to the battery.."
Not a possibility, these are PERMANENT magnet rotor synchronous AC motors. As long as they are TURNING via external force they WILL geneate voltage on the windings. Unless "something" is to alleviate the possibility the generated voltage will rise high enough to damage the solid state electronics.
That "something' is generally finding a way to "drive" the motor slightly faster than it would otherwise be driven.
I did not imply removal of the AC field. I said removing the "charging loop to the battery" That is the DC side. True, the windings will still generate a potential either as a flux (open armature circuit) or as a voltage (closed armature circuit, but with no connection to the DC path as far as the battery,
so there is no charge voltage and thus no charge current.
Sorry, but if you open the stator output of "these" motors while they're still rotating the voltage output will rise as high as need be to find, or open, a current flow path.
The AC from MG2 is utilized in a different manner once the battery charge is removed. (I'll leave it to you to figure that one out. HINT: What happens to MG2 when you are going down an extended downhill grade, the ICE is in fuel cut-off, and the battery reaches the maximum SOC scheduled by the ECU? Kinetic energy is still being applied and the drive train is feeling large amounts of negative torque. MG2 is still producing a field, so where does it go? ANOTHER HINT: The relationship between MG2 and MG1 is more than just mechanical across the PSD.)
In the same way the vehicle is kept stationary with the ICE idling. The e/CVT is simply a more complex "summing" engine/device than an open differential. You simply negate the ICE drive by counter driving the MG/MG's.
In your case the battery would be called upon to supply enough AC drive to both MGs to "drive" the motors just fast enough to negate any "reverse" (regen) drive.
Time for "B", engine compression, mode.
