Is regen based on motors?

ricinro

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conversely, pumping (work-energy) electrons through a conductor can create a magnetic field that pushes or pulls on a magnet.

https://en.wikipedia.org/wiki/Electromagnet

Regenerative braking uses the kinetic energy of the vehicle to generate electrical energy using the motors and this recharges the batteries.

I can't say for sure how much range in an EV is attributed to the scavenged energy of regenerative braking. I have seen estimates from 8% to 32%
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TyPope

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So... I understand that physics dictates how much energy is available to be "regened" when slowing... I also know there are inefficiencies within the motors... Question here is How much of a difference in regen will there be between a single-motor and a tri-motor CT? Is it more efficient to spread the stopping power among several generators or is it better to run a single motor harder? Would a tri-motor limit which motor is in regen to optimize electricity generation? Is there a limit on how much each motor can regen at any given moment?
 

ajdelange

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Regeneration occurs whenever the wheel absorbs torque from the road. Mototring occurs whenever the wheel transmits torque to the road. Thus if you are going along at 70 and back off the pedal the "motor" will absorb torque, the vehicle will slow and your power gauge will show negative power. The same thing happens as you back off the pedal to maintain speed when cresting a hill. As the speed stays the same the kinetic energy of the vehicle remains the same. To keep the speed constant the vehicle must apply, by absorbing torque, thrust in the uphill direction just sufficient to balance the pull of gravity which is trying to accelerate the vehicle down the hill. The power gauge also reads negative in this case and the battery is being charged. I once did a trip of about 22 miles where the battery indicated 2% more charge at the destination than at the departure point.

In this downhill example the "motors" are converting the gravitational potential energy of the vehicle to electrical energy.

How much range is attributable to regen is difficult to calculate because it depends both on how much energy is collected from regen in your recent past driving and how much energy you will use per mile in the future drive. In the example I gave above I went 22 miles without using any energy at all. In fact I gained some. At the stop I had an extra 2 kWh aboard, all from regen. Normally that would take me 6 miles. What we can say is that if you increase the sum of the kinetic or potential energy of the vehicle by 1 kWh you will have used about 1.11 kWh from the battery to do that. If you come back down hill the same amount or slow down those energies are absorbed by the motor(s) which convert them back to electricity also at less than 100% efficiency so 1 kWh absorbed by the wheels may put 0.9 kWh back into the battery. The regen "round trip efficiency" is 0.9*0.9 = 81%. You will recover 81% of your inertial and gravitational loads. As the former is a large load in driving where you must accelerate and decellerate a lot the recovery can be a significant contributor to your range. Similarly, in hilly country potential load can be large and you will do a lot better with regen than without. But the actaul range added depends on the actual conditions,
 

ajdelange

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Ty,

The amount of torque extracted from each motor can be independently controlled. Thus if the synchronous motor is a little more efficient than the induction one we could, when torque must be absorbed, take it from the synchronous motor first and only take it from the induction motor when the synchronous motor can't absorb as much as we need to absorb. This is the reverse of the philosophy for motoring mode where, it is believed - don't take any of this as gospel - that the synchronous motor is used preferentially in cruise (because it is more efficient) with the induction motor used for the high torque needed for acceleration. I am describing the X which has one of each.
 

ldjessee

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There is also the limit of the battery and how much energy it can accept safely, though with the way Tesla battery packs are built, this is quite a lot, but I am not sure how much exactly.
 


TyPope

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There is also the limit of the battery and how much energy it can accept safely, though with the way Tesla battery packs are built, this is quite a lot, but I am not sure how much exactly.
That's kind of what I was getting at. There's only so much energy that one of the motors can capture and feed to the batteries. If the limitation is the rate at which the battery can charge, there would be no efficiency advantage that the tri-motor would have over the single motor (assuming the single motor could charge the battery at the battery's optimal speed). However, if the regen limitation is that the motors can't provide as much of a charge as the battery can take, then having more motors would allow you to get closer to the max charge rate of the battery. IF this is the case, perhaps a four-motor model would be more efficient than a single motor version...
 

ldjessee

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That's kind of what I was getting at. There's only so much energy that one of the motors can capture and feed to the batteries. If the limitation is the rate at which the battery can charge, there would be no efficiency advantage that the tri-motor would have over the single motor (assuming the single motor could charge the battery at the battery's optimal speed). However, if the regen limitation is that the motors can't provide as much of a charge as the battery can take, then having more motors would allow you to get closer to the max charge rate of the battery. IF this is the case, perhaps a four-motor model would be more efficient than a single motor version...
The Tri-Motor will have a bigger battery pack, so even more cells to spread that captured energy over, so probably even more capable of accepting energy than the current Tesla battery packs... Assuming that Tesla keeps the same cell/battery architecture they currently have.

If the motor can output it, it can accept it. The wiring, electronics, and battery would be things that would need to also handle the energy that is produced.

I could see going down hill with just a decent cargo in the bed (say 1/2 the capacity, or 1,750 lbs) plus the weight of the CyberTruck allowing for lots of energy to be generated... some places I have driven with a 6% grade for 12 miles. Lots of warnings for semis...

There is potential for lots of energy to be generated and possible that you could recharge the battery completely and then have to use the disc breaks... :ROFLMAO:
 

ajdelange

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You do not want to overcharge the battery under any conditions and you do not want to charge it too fast when it is cold (or, most likely, hot either). Thus the vehicle reduces or disables the amount of regenerative braking available when the battery is close to fully charged (another reason to charge below 90%) or when it is cold.

The motor is a symmetric device. Thus it can, presumably, absorb as much power as it can produce. Thus there is, ostensibly, no advantage to having more motors from the regen perspective. But I'll note that the power meter on the X goes up to +350 kW but only down to -75.

The battery pack in an X can accept charge at rates up to, I think, 200 kW in low SoC conditions but that is tapered as SoC increases. Thus on a long downhill grade with 14,000 of trailer behind you there might be some additional limitations on regen (though, of course, we would hope the trailer would have some braking of its own).
 

TyPope

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You do not want to overcharge the battery under any conditions and you do not want to charge it too fast when it is cold (or, most likely, hot either). Thus the vehicle reduces or disables the amount of regenerative braking available when the battery is close to fully charged (another reason to charge below 90%) or when it is cold.

The motor is a symmetric device. Thus it can, presumably, absorb as much power as it can produce. Thus there is, ostensibly, no advantage to having more motors from the regen perspective. But I'll note that the power meter on the X goes up to +350 kW but only down to -75.
Hmm... You use the equivalent of about 260 Wh/mile, right? It would be nice to be able to regen faster than you use it on average as many times, the deceleration can be more sudden than the acceleration. I'm still new enough that I'm almost certain I accelerate (use energy) at a much larger rate than I decelerate (produce energy)... But, I DO grin the whole time.
 

ldjessee

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Hmm... You use the equivalent of about 260 Wh/mile, right? It would be nice to be able to regen faster than you use it on average as many times, the deceleration can be more sudden than the acceleration. I'm still new enough that I'm almost certain I accelerate (use energy) at a much larger rate than I decelerate (produce energy)... But, I DO grin the whole time.
I would like to ride my motorcycle in the rain and not get wet...
 


ajdelange

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Hmm... You use the equivalent of about 260 Wh/mile, right? It would be nice to be able to regen faster than you use it on average as many times, the deceleration can be more sudden than the acceleration. I'm still new enough that I'm almost certain I accelerate (use energy) at a much larger rate than I decelerate (produce energy)... But, I DO grin the whole time.
Yes, 260 is close to the rated for my car but I tend to average about 270. Using that much while driving 65 mph at exactly uniform speed would show 17.5 kW on my power meter. If I accelerate or decelerate the magniutde of the number is much bigger than that - nearly always higher during acceleration than conversely. But Tesla limits the number of negative g's you pull based on vehicle speed and that has a big effect on things. Some manufacturers have levels of regen. With Tesla it's on or off.
 

TyPope

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I would like to ride my motorcycle in the rain and not get wet...
Well, the ability to put electricity into the battery FROM the motors when braking hard at a rate that is higher than when driving is PROBABLY already being done. I haven't seen the figures on limitations so I was making a guess. I don't think you'll have much luck riding in the rain and not getting wet. I get wet even when wearing rain gear. But, the sarcasm is sort of appreciated.
 

ajdelange

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Yes it is, definitely. Look at your power meter as you drive at constant speed and then take your foot off the accelerator.
 

Dids

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Does it matter if you are driving east vs west?
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