It’s not using the battery if it’s plugged in. It’s using the power from the wall up to the current limit set by the user and supplementing it with battery power as needed.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Limiting Charging Amps
- Thread starter dansev
- Start date
Are we certain of this? If that's the case, I guess I should not limit to 32A. Probably a dumb idea anyway.
Benito1283
2021 MYLR 19"
Yes we are certain. I think 32 amps should cover most if not all of what the car would use.
davewill
Active Member
I actually think you would be just fine. I'd be surprised if the HVAC drew more than a few amps @ 240v. It is unlikely to have any effect on your battery level, especially if the battery is full or nearly full when it comes on. The only time I've ever heard of wall power being unable to keep up with heating and drawing the battery down is in freezing temps on a standard 120v wall plug.
ucmndd
Well-Known Member
The resistive heater in earlier cars can draw nearly 5kw at full tilt (20+ amps at 240v).
Not sure about the heat pump but I’m sure it’s more than “a few”.
I'll check it later, but I'm pretty much positive that it'll use the 240V circuit if the HVAC is turned on after its plugged in. The experiment I did that said otherwise was having plugged in(started charging), I turned HVAC on, then pressed 'stop charging' on the app. This definitely stopped the 240V supply from powering the HVAC.
I can say for sure that this morning after my car was sitting all night plugged in(and completed charging last night in the middle of the night) after I turned the HVAC on, the scrolling green lights were running on the HPWC. It may have decided to start charging as well, though.
Benito1283
2021 MYLR 19"
From memory, experience and what I have read follows is how power is used from a plugged in HPWC on the original NONE heatpump Model 3's.
The resistive heating elements can draw up to 7KW. (I have measured this using a DC current clamp, I did see a max of around 7KW but that power level draw only lasted a short time).
The rear motor stator can draw up to a max of 4KW.
The front motor stator can draw up to a max of 4KW (my buddy who owns a dual motor 2019 has never seen a power draw of greater than 3.5KW using SMT).
So if your Wall Connector/car was set to deliver/receive 32A and the voltage was say 235V you would have approx 7.5KW on the input side of the cars AC charger. The output side of this AC to DC conv is connected to the same HV buss as the traction battery; therefore, if the power required for HV battery conditioning and/or the HVAC is more than the 7.5KW available from the wall, the remaining power would come from the HV traction battery. If the car was also trying to charge the HV battery, it would only add energy/miles to the battery when the power draw dropped below 7.5KW is this example. So drawing power from the Wall Connector would add less wear and tear to the HV traction battery due to the fact that less or possibly no energy would be required from said battery.
So for my long range rear motor 2018 Model 3 the max power draw would be 4KW for the rear stator and 8KW for HVAC. So with the approx 11.5KW (240V X 48A) of energy available from the Wall Connector, energy from the HV traction battery should almost never be required.
The resistive heating elements can draw up to 7KW. (I have measured this using a DC current clamp, I did see a max of around 7KW but that power level draw only lasted a short time).
The rear motor stator can draw up to a max of 4KW.
The front motor stator can draw up to a max of 4KW (my buddy who owns a dual motor 2019 has never seen a power draw of greater than 3.5KW using SMT).
So if your Wall Connector/car was set to deliver/receive 32A and the voltage was say 235V you would have approx 7.5KW on the input side of the cars AC charger. The output side of this AC to DC conv is connected to the same HV buss as the traction battery; therefore, if the power required for HV battery conditioning and/or the HVAC is more than the 7.5KW available from the wall, the remaining power would come from the HV traction battery. If the car was also trying to charge the HV battery, it would only add energy/miles to the battery when the power draw dropped below 7.5KW is this example. So drawing power from the Wall Connector would add less wear and tear to the HV traction battery due to the fact that less or possibly no energy would be required from said battery.
So for my long range rear motor 2018 Model 3 the max power draw would be 4KW for the rear stator and 8KW for HVAC. So with the approx 11.5KW (240V X 48A) of energy available from the Wall Connector, energy from the HV traction battery should almost never be required.
Last edited:
Prepare to be surprised. It uses a lot more than a few amps @ 240V. Heat pump or no. My 2021 heat pump car drops about 2% charge when preconditioning when plugged in to a 240V 30A circuit.
Ok, so the results are in.. Stacy's Mom(my 2018 AWD 3) will take around 30 amps(7+kw) continuously during cabin heating. Its a wee bit above that initially, but settles down quickly, and ramps down further as the cabin warms up.
As I stated before, turning down the current(in the car) to 5 amps means it will take no more than 5 amps no matter what sequence is used or what is turned on or off.
Interestingly... if the car is charging and the HVAC is turned on, and then you command the car to stop charging, The drawn power goes to 0 and all HVAC keeps running but its power is drawn from the battery. If you then turn HVAC off and back on, it reconnects to the HPWC power and draws whatever it needs(up to the limit set in the car).
As I stated before, turning down the current(in the car) to 5 amps means it will take no more than 5 amps no matter what sequence is used or what is turned on or off.
Interestingly... if the car is charging and the HVAC is turned on, and then you command the car to stop charging, The drawn power goes to 0 and all HVAC keeps running but its power is drawn from the battery. If you then turn HVAC off and back on, it reconnects to the HPWC power and draws whatever it needs(up to the limit set in the car).
Wow--it sounds like you've discovered a very strange hole in the programming logic. I'm pretty sure it's not really intended to do that.
The battery can supply more instantaneous current than any AC charging setup, and so might cause a short term drop in battery SOC, especially if the heating occurs just before the charging session is terminated. AIUI, the battery is only used when the current for HVAC and battery heating exceeds the AC charge current.
This is how it should be. The car should never draw power from an external source when you command it to stop using external power.
The amp limit exists to protect the AC circuit and, again, the car should never, under any circumstances, exceed the set amp limit.
The command was to 'stop charging' not 'stop using external power'.
And yes, the car should never exceed the set amp limit. I only did the test because earlier in this thread there was/were at least one comment saying that the HVAC would ignore the set amp limit.
stopcrazypp
Well-Known Member
Your results make sense because I remember reading that for people on charging on 120V circuits, when charging in very cold climates, the charge actually may go down (as there is not enough power for the overhead losses to heat the battery). If the HVAC ignores the set amp limit, then that wouldn't happen (but would be pretty dangerous for those with flaky circuits).
The car can only use external power when commanded to start charging; it has no programing to do otherwise.
Similar threads
- Question
