I think we are talking two different cases, I'm thinking of when the vehicle is not in motion.
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Model 3 Battery Heating?
- Thread starter ratsbew
- Start date
I think we are talking two different cases, I'm thinking of when the vehicle is not in motion.
Just to be 100% clear, the motor part of the drive unit, not the inverter.
That was Big Earl's number.
I think the pic I posted is the assembly on the left side of the total unit in the video you posted.
If the dud have a double wall setup with oil in the gap, that would help with heating efficiency, but I don't that that is the setup.
Is there any direct oil cooling of the motor, or is it all conduction to the gear train section?
hacer
Active Member
How would you pre-condition the battery on your way to the supercharger unless the "heater" can run while the motor is operating?
The large Model S/X motor has a an efficiency of aprox 92-93% at peak power. At 20 kW cruising it is 88%. The smaller Model S/X is known to be more efficient. The Model 3 motor is even more efficient than that.
I'm not saying the drive unit doesn't also provide heat while driving. I'm just talking about the case where the car is not moving and is heating the pack. However, if you are doing 70 though frozen roads (or worse, slush) to a Supercharger, it seems like using the motor heat via drive unit case conduction would be even less efficient.
The pack is on one loop to the 4 way valve, the other loop is penthouse electronics, inverter, and then oil heat exchanger. The oil pump is switched, so they could avoid pumping cold oil through the heat exchanger to retain as much heat from the electronics as possible.
Via which methods?
- Oil flow through the rotor shaft
- Oil flow around the shell/ stator of the motor
- Conduction to the gear section that is filled with oil
hacer
Active Member
Best video I've seen of the encoder end of the motor:
So the entire motor is bathed in oil, good cooling for the windings and rotor. Gives a much better heat path than what I was wrongly imagining.
Could it also be they are using induction to heat the rotor and oil, then onto the pack? Normally, the SR motor rotates synchronously with the stator field, so there is no flux change in the rotor and little loss. However, if they also impose a sinusoidal field, then the rotor could act like a shorted winding. Like what happens in an AC induction motors, but without rotating the field so there is no mechanical movement. That could increase the power dissipation without needing as much current in the windings.
Could it also be they are using induction to heat the rotor and oil, then onto the pack? Normally, the SR motor rotates synchronously with the stator field, so there is no flux change in the rotor and little loss. However, if they also impose a sinusoidal field, then the rotor could act like a shorted winding. Like what happens in an AC induction motors, but without rotating the field so there is no mechanical movement. That could increase the power dissipation without needing as much current in the windings.
hacer
Active Member
Great. Could you do a full-throttle launch and post a plot of motor efficiency and motor power as a function of speed (at least up to peak power output) when you have a chance? Thank you.
I have done that a few times. Somewhere buried in hundred of log files
Here is what I wrote down from freeway driving.
efficiency Tesla Model S 85 (RWD)
12 kW = 82%
20 kW = 87%
36 kW = 90%
42 kW = 91.5 %
50 kW = 92 %
Speed is km/h
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I think you may find the "Smart Battery Prep" app I released last week useful (this feature is included in the Stats for Tesla app):
Smart Battery Prep: For Tesla
It adds a top-off charge at the designated time so that the battery is conditioned by the time you intend to use the car.
More details here: https://www.maadotaa.com/batterycond
In Bjorn's recent video he now has a CAN bus adapter and can view all kinds of stats on the Model 3. When he started charging it ramped both the front and rear motor up to 3.5 kW to heat the battery. So the Model 3 can provide 7kW of heat for the battery even without a dedicated battery heater.
Which begs the question: how does the rear wheel drive Model 3 perform? Does it only do 3.5 kW or can it do the full 7 with just the rear motor?
eprosenx
Active Member
I think it may only be able to do 3.5kW of heating. :-( I don’t see a huge spike in shore power usage when I tell the car to pre-heat.
