Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Preconditioning - Am I Missing Something?

This site may earn commission on affiliate links.
Here's some data from today at lunch. Captured (with scanmytesla) min battery temps, power consumed on front and rear motors and total power used (which also includes cabin heating). PTC heater, no heat pump.
Cool stuff! I've only read a bit about scanmytesla, obviously I need to read more. I have to admit the special wiring harness is a bit intimidating.

Thanks to all who replied.
 
Here's some data from today at lunch. Captured (with scanmytesla) min battery temps, power consumed on front and rear motors and total power used (which also includes cabin heating). PTC heater, no heat pump. Outside temp was -14C. Temps in degrees C, energy in kW.

View attachment 751882

I did not have the cabin temp notification turned on so I don't have the exact time. When I checked the cabin temp (I think around 12:12-12:14) it was already at 21C. It doesn't take long. The last line is from when I got in the car and put it in drive without moving. Active battery heating stops then.

20 minutes at an average of 11kW means a consumption of 3.7kWh, that's significant energy.

EDIT: Important note: subject to change with software updates... it was different last year.
Useful data. Thanks.
 
Last winter I would precondition for 30 minutes or longer before driving my 2020 LRMY but I would still start out with limited regenerative braking.

With the latest release I precondition for between 5 and 10 minutes (might take a bit longer as we move into the coldest winter months). I receive a notification from the Tesla app on my phone that the passenger cabin of my Model Y has reached the desired temperature (71F). I no longer see the bacon symbol indicating that the battery is being warmed. I have some regenerative braking when I start driving, not full regen but enough to be useful when driving.

The strange thing is sometimes I get the warning message that Regenerative braking has been reduced due to temperature when it is relatively warm, i.e. 50F (10C) and other times there is no message an the temperature is actually a bit lower. My Model Y is always parked inside my attached garage. The garage temperature is generally 10 degrees higher than the outside air temperature.
AFAIK, at 50F and a high SOC you will probably get the message at a lower SOC you might not. I have no idea where the temp/SOC points are for displaying the message versus not. Be nice to have a graph of SOC versus temp showing about when the message is shown. I believe there is a SMT parameter that show how much regen is possible that is probably used to make the call.
 
What I've heard in general is that's it's never useful to fully condition the battery without being plugged, it's always a net negative. The positive side is gaining your regen so it's more of a driveability thing. When plugged in, you're still paying for the energy but at least it doesn't come out of your battery.
Last week I had an interesting case: staying at a ski village which was about 700 vertical metres above the valley floor, with the car unplugged. With cold winter conditions, over a few trips I drove down to the valley floor both with and without running the climate long enough to warm up the battery before leaving. Without a warm battery, there was no regen for most of the descent (+ ~1 % SOC), while with it warmed there was regen for the whole way down (+ ~5% SOC). In this special case, I found that at minimum having the regen recovered the energy used to precondition the battery, and likely gave a net positive over starting with a cold battery.
 
Anybody have any idea why my home charger which is 40 amps (and has always worked near that number) now only charges at 8 amps? It’s been very cold outside, but scheduled the charge which should have preconditioned if that’s the issue. In car charging screen set to 40, app allows no more than 8 amps. Start of the problem coincides with both the latest software update and the colder (14 degrees or so) weather. Help appreciated!
 
Anybody have any idea why my home charger which is 40 amps (and has always worked near that number) now only charges at 8 amps? It’s been very cold outside, but scheduled the charge which should have preconditioned if that’s the issue. In car charging screen set to 40, app allows no more than 8 amps. Start of the problem coincides with both the latest software update and the colder (14 degrees or so) weather. Help appreciated!
The Tesla Model Y's on-board charger is detecting a voltage drop, lowers the charging amperage to prevent an overload condition. Have an electrician check all of the connections for the 40A circuit and EVSE.
 
  • Like
Reactions: GtiMart
Anybody have any idea why my home charger which is 40 amps (and has always worked near that number) now only charges at 8 amps? It’s been very cold outside, but scheduled the charge which should have preconditioned if that’s the issue. In car charging screen set to 40, app allows no more than 8 amps. Start of the problem coincides with both the latest software update and the colder (14 degrees or so) weather. Help appreciated!
If your battery cells are down near 14F and you own a dual motor, approx 32A of the power could be going towards heating the battery via the dual motor stator windings. Leaving the remaining 8A to go towards charging the HV battery (this assumes the cells are warm enough to accept 8A). As the cells warm, during the charging session, more of the power will go towards charging and less towards heating. Now if the Wall connector is only delivering 8A that is a different story. If your car is a heat pump Model, not sure exactly how HV battery heating/charging is handled. BTW, not sure how your pre-conditioning plays into this.

3.5KW to front motor + 4KW to rear motor + 250W car awake overhead = 7.75KW

7.75KW / 240V = 32.3A

SMT would be great tool to determine what is actually going on. If the motor(s) are being used to heat the HV battery, you should be able to hear a whine for one or both.

Also, could be what jcanoe suggested.
 
  • Like
Reactions: Rocky_H and GtiMart
The Tesla Model Y's on-board charger is detecting a voltage drop, lowers the charging amperage to prevent an overload condition. Have an electrician check all of the connections for the 40A circuit and EVSE.
For the voltage drop thing, it will drop to three fourths of the original charging current and try again. If that still has too much drop, it will shut off. 8 out of 40 isn't that.
I'm pretty sure it's what @rrolsbe is mentioning. At a cold snap of 14 degrees, the car's screen display will show a very small number of amps of actual charging (sometimes 0), while it is diverting a lot of amps toward the car's heating systems trying to warm the battery. After some time (half hour? an hour?) it should be warming up more that it can shift more of the amps into charging, and it should keep climbing upward from 8A.
 
For the voltage drop thing, it will drop to three fourths of the original charging current and try again. If that still has too much drop, it will shut off. 8 out of 40 isn't that.
I'm pretty sure it's what @rrolsbe is mentioning. At a cold snap of 14 degrees, the car's screen display will show a very small number of amps of actual charging (sometimes 0), while it is diverting a lot of amps toward the car's heating systems trying to warm the battery. After some time (half hour? an hour?) it should be warming up more that it can shift more of the amps into charging, and it should keep climbing upward from 8A.
The only time I observe my 2020 LRMY using less power than can be supported by the charging station is after charging has been completed and my Model Y is being preconditioned. On a 6kW maximum charging session the Tesla screen will sometimes display 2kW or 3kW being used while preconditioning. The climate control system is warming the passenger cabin after battery charging has been completed. I have never observed a reduced charging rate, i.e. 8A out of a possible 32A in the case of my home charging setup. The amperage never varies by more than 1A. I usually monitor charging via the Tesla app as my Model Y is parked in a public garage some distance away or in my garage when charging at home.
 
  • Like
Reactions: Rocky_H
The only time I observe my 2020 LRMY using less power than can be supported by the charging station is after charging has been completed and my Model Y is being preconditioned. On a 6kW maximum charging session the Tesla screen will sometimes display 2kW or 3kW being used while preconditioning.
Yes, that's still part of the same thing I was mentioning. Diverting power to heating is still diverting power to heating, whether that's for the cabin or for the battery. Either way, they won't show up in the amps of charging.
 
Yes, that's still part of the same thing I was mentioning. Diverting power to heating is still diverting power to heating, whether that's for the cabin or for the battery. Either way, they won't show up in the amps of charging.
I did a 1.25 hour charging session, added 7kWh (30A @ 200V). I intentionally stopped charging via the app, then started preconditioning. The Tesla app showed 5A with an occasional 30A reading, i.e. 1kW being consumed at a minimum during the preconditioning period. The battery was warm so the heat pump was able to use coolant from the battery to warm the passenger cabin. Still, 1kW seems like low power demand for warming up the cabin.

The Chargepoint charging station displayed 0W being consumed, with a status of charging completed from the time charging ended and during the preconditioning period. The battery SOC lost 1% during the preconditioning period of ~10 minutes. This made me think that the Tesla Model Y will draw some power (perhaps a few kWh) from the battery while preconditioning before replenishing the battery if the Tesla vehicle is plugged in.