If you look at the video I posted....the heat exchanger isn't on the motor. We touched the heat exchanger earlier today and it was warming up to the touch. I never got hot...just about 50 degrees or so.
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Cold. Cold. Cold. Strange / Interesting screen reading.
- Thread starter Garlan Garner
- Start date
If you look at the video I posted....the heat exchanger isn't on the motor. We touched the heat exchanger earlier today and it was warming up to the touch. I never got hot...just about 50 degrees or so.
I was just speaking with a guy who replaced the bearings on a Model S just like this guy is doing. He indicated that at exactly 2.18 in the video we can see the neutral setting where the Motor shaft is disengaged from the drive gears ( neutral ).
The left most gear is the motor. The middle gear is the selector and the right gear turns the axels. The guy is holding on to the lubricant gear. He said...you can see in this video that the motor gear is not attached to the gear selector so in this case the wheel and motor are not attached together. (essentially neutral).
You guys are stretching my knowledge about all of this stuff....so I can still be dead wrong. I'm just relying on people who know more than me.
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AlanSubie4Life
Efficiency Obsessed Member
I think it's possible to generate heat from a motor that is not spinning. It seems like it might be tricky (you don't want it to spin by mistake - I did see your video of the Model S, comments on that below...), but it seems possible to do this if you have individual control of the phases in the poles/motor windings (which they surely do). I would think it would be more effective to use the rear motor to do this (PMSRM) as I thought it was easier to cool than induction motor, since the rotor doesn't heat up much while the stator does (so it follows that it would be easier to extract heat from it too).
Honestly, if the OP numbers are to be believed, I don't have another explanation for the huge amount of draw that he saw. We have quite a bit of circumstantial evidence posted here to indicate that the PTC heater (which does exist), is about 10-12kW max. I have no idea how the heat from that is exchanged with the cabin (does it use a coolant loop to a heat exchanger or does cabin air go through it directly)? Would be obvious if someone looked in a teardown. The way it looks in the part diagram I guess it's just airflow, but no idea. The part diagrams are lacking in assembly detail...
It makes some sense for the motors/battery & the cabin heat to be separate. That way you're not dealing with excess heat to the motor cooling loop, if someone decides to turn on cabin heat to max. Though they do have ways to route heat with the Superbottle, so who knows. Still, probably separate.
In any case the OP saw 25kW of drain (25kW*0.75hr / 0.242kWh/mi = 77 miles), so that seems more than you could ever get from just the cabin heater. So it does seem like there's some other energy drawing source. Motor seems like the only other reasonable candidate.
Interesting. There is coolant flowing through there too so I don't know whether you felt spinning or the flowing of coolant or vibration of a stalled motor or what. Even if they aren't using the front motor for heat you might still experience warming since the loops are connected somehow. Or maybe they're also using the front motor...
Seems possible/likely.
It's definitely got ways to convert electrical energy to heat if it's excited in the correct manner. You've got resistive losses in the windings, you can generate eddy currents, generate equal and opposing forces which each generate heat but provide no net torque, etc. And presumably they have complete control over exactly how they excite each of the motor poles. But no idea whether they actually do this. Based on the OP, I would guess they do.
I looked at 2:18 in the video for a while. It's actually hard to see whether the gears are meshed or not (motor and selector)...if you look at where the shafts for those gears go into the housing later in the video, they are fixed position, so I don't understand how they could go from not engaged to engaged... I'm not saying I don't believe what your guy says - I just can't tell whether the gears in question are meshed, and I can't tell how they would move (to engage/disengage), even if they aren't meshed. And normally this is not how gears are meshed with one another...usually gear lash and engagement has to be super precise so adding a moving engage/disengage seems difficult. Gearboxes have synchros and dog teeth engaging the side of the gears for this reason, I thought...the actual engagement points that do the reduction are always engaged...on all the gears. (Though reverse gear I guess is an exception on cars without reverse synchros - have no idea how reverse synchros are implemented.)
Anyway, I would think you'd hear the motor spinning quite audibly if it were actually spinning and somehow disengaged...
Honestly, if the OP numbers are to be believed, I don't have another explanation for the huge amount of draw that he saw. We have quite a bit of circumstantial evidence posted here to indicate that the PTC heater (which does exist), is about 10-12kW max. I have no idea how the heat from that is exchanged with the cabin (does it use a coolant loop to a heat exchanger or does cabin air go through it directly)? Would be obvious if someone looked in a teardown. The way it looks in the part diagram I guess it's just airflow, but no idea. The part diagrams are lacking in assembly detail...
It makes some sense for the motors/battery & the cabin heat to be separate. That way you're not dealing with excess heat to the motor cooling loop, if someone decides to turn on cabin heat to max. Though they do have ways to route heat with the Superbottle, so who knows. Still, probably separate.
In any case the OP saw 25kW of drain (25kW*0.75hr / 0.242kWh/mi = 77 miles), so that seems more than you could ever get from just the cabin heater. So it does seem like there's some other energy drawing source. Motor seems like the only other reasonable candidate.
Interesting. There is coolant flowing through there too so I don't know whether you felt spinning or the flowing of coolant or vibration of a stalled motor or what. Even if they aren't using the front motor for heat you might still experience warming since the loops are connected somehow. Or maybe they're also using the front motor...
Seems possible/likely.
It's definitely got ways to convert electrical energy to heat if it's excited in the correct manner. You've got resistive losses in the windings, you can generate eddy currents, generate equal and opposing forces which each generate heat but provide no net torque, etc. And presumably they have complete control over exactly how they excite each of the motor poles. But no idea whether they actually do this. Based on the OP, I would guess they do.
I looked at 2:18 in the video for a while. It's actually hard to see whether the gears are meshed or not (motor and selector)...if you look at where the shafts for those gears go into the housing later in the video, they are fixed position, so I don't understand how they could go from not engaged to engaged... I'm not saying I don't believe what your guy says - I just can't tell whether the gears in question are meshed, and I can't tell how they would move (to engage/disengage), even if they aren't meshed. And normally this is not how gears are meshed with one another...usually gear lash and engagement has to be super precise so adding a moving engage/disengage seems difficult. Gearboxes have synchros and dog teeth engaging the side of the gears for this reason, I thought...the actual engagement points that do the reduction are always engaged...on all the gears. (Though reverse gear I guess is an exception on cars without reverse synchros - have no idea how reverse synchros are implemented.)
Anyway, I would think you'd hear the motor spinning quite audibly if it were actually spinning and somehow disengaged...
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You guys have far exceeded my ability to know exactly what's going on concerning the heat.
I just know from a lamens point of view that the heat exchanger warmed up this morning and the water started flowing in the white plastic bottle and the battery was supposedly warming up a bit.
Thanks for your knowledge.
AlanSubie4Life
Efficiency Obsessed Member
He obviously wanted to optimize his efficiency stats. Makes things look awesome when it's not counted.
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As a meteorologist, let me second Eriamjh1138's reply. Wind chill only applies to humans. It's actually only an estimate of how fast exposed skin will lose heat with "no wind" if the observed temperature were equal to the wind chill temperature. As wind speed increases, the rate of cooling on exposed skin increases as if the temperature were at the wind chill temperature and the actual wind speed were less than 4 mph ("no wind").
An ICE car (and it's coolant/anti-freeze) will cool of faster the lower the wind chill. Otherwise, the car could care less what the wind chill is. Maybe helpful to remember as CHI heads to -21F later in the week.
I've rebuilt many dozens of FWD transmissions. I can tell you from those pics that it is a fixed one speed gearbox. That is the intermediate reduction idler, and there is no provision for a selector as there are no shafts or yokes to move anything. It really seems like a solid box and the size of the ring gear is impressive. The input gear is rather undersized though.
You should tell Tesla that the input gear is undersized.
If its the same one that's in my P3D+ then it does an excellent job getting me from 0-60 in 3.1 seconds.
Would a bigger one help me get a faster time?
I'm not saying it's a weak point. I'm just making an observation. It is interesting to see.
Why take everything so negatively?
The engineers who designed it know more than I ever will about the strength of the components. The input needs to be compact so you have some speed up top. The box would be far larger if you made that input gear 1 inch larger in diameter.
But it is a fixed one speed box with no neutral position.
I have been using a 110v outlet at work mainly to keep the battery warm and to minimize vampire drain throughout the day.
Basically if it is below freezing it will not gain any charge. Depending on how cold it is, it will loose charge while plugged in as well.
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No it can't. The motors are always geared directly to the wheels. There is no clutch.
AlanSubie4Life
Efficiency Obsessed Member
Technically I guess this might be the case, but it's definitely part of the drive unit. And the location of the heat exchanger is not an indicator of where heat is generated, exactly...presumably the oil picks up the heat from the drive electronics & the stator (and to a lesser extent the transmission components), and there's an oil/coolant heat exchanger (as Munro says). More of a description of the rear motor, I guess. For the front motor I don't know how they cool the rotor (I don't know how that heat is conducted to the outside world).
But again, though you were feeling the heat at the front, it's possible that most of that heat was generated by the rear motor. It's not clear that there would be an entirely separate loop for the front motor (and Munro's diagrams are for RWD so don't cover that). I guess there probably is a separate loop, but I don't know. But separate or shared, the coolant in the system will warm up as the system pumps coolant around.
Well, since you volunteered. These experiments are not very exciting though. Personally it would be nice to answer the question raised in this thread - take some data and measure how much power preheating takes at -15F when it hits that on Wednesday. I'm actually curious about a few things, partially behaviors and partially quantitative info:
1) Preheat energy use when you're not in the car. (Seems to be at least 25kW according to one poster here.)
2) If you're in the car with the car on, in drive, STATIONARY, but you turn off HVAC, does it continue to warm the battery if it is extremely cold? You could measure this too by tracking rated miles (and also the Wh/mi in your trip meter).
3) Describe how the cold battery mileage is accounted for. I know it reduces available miles but I don't know how this is displayed.
Since its going to be -24.
Do you drive to work and let it sit all day unplugged? I'm curious about heat when there is no possibility of pre warming.
Such as getting a call at work to pick up a sick child asap. Walk out to the car and go.
This topic really went off the rails. I’ve rebuilt transmissions before and can tell you there is no provision to mesh/unmesh gears in the video above. Tesla has stated that they send energy to the M3 motor in a manner that results in the motor not spinning, but instead the energy is converted to heat by the motor’s resistance. So, yes, the motor can be stalled and just generate heat.
As to the question of differentials, Tesla uses normal open differentials. Limited slip diffs would be nice, but they get a similar effect by having the traction control system selectively apply braking to a slipping wheel.
As to the question of differentials, Tesla uses normal open differentials. Limited slip diffs would be nice, but they get a similar effect by having the traction control system selectively apply braking to a slipping wheel.
I'm anticipating that my P3D+ will probably be one of the few cars guaranteed to "start" and instantly move.
On the other hand...I wonder if my 12V battery will be kept charged by the battery pack enough to not be an issue as I'm sure all of the other ICE cars may have.
I have about 16 tests to run so far.
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