Power consumption while plugged in and not charging

[joosh]

I am just two weeks into owning my M3 and have been charging to 80% at night on a schedule. I typically charge from 57% for a total of 23% charge which for a 75kw battery equates to ~18kw. I’ve noticed my daily kw avg consumption at home jump by at least 25kw per day since I started charging my M3 at home. We’re not doing anything different at home energy wise and I understand that’s a big variable, but I’m wondering if my M3 is using power from the plug while waiting to charge on its schedule? My garage right now is averaging 50 degrees F at night. Just trying to figure out where the 25kw is coming from when it should be around 18kw. Any thoughts?

 

[joosh]

Also, I’m using a Nema 14-50 outlet on a 60amp circuit

 

[al503]

There is a certain amount of resistance during charging that turns the energy into heat instead of actually charging the battery.
As I understand it, some of the charge may also be used to maintain certain battery temps that will prolong/increase battery longevity.

 

[animorph]

If the car is plugged in but not charging it will draw from the charger to power the car when you turn it on. Like if you're sitting in the car playing with the display or the car is updating. If the battery heater has to run in really cold weather that's power that is used without going into the battery first.

Maybe 10%-20% losses just getting the energy into the battery, especially when it's making the run all the way from your house power meter, through the Tesla connector, into the car, through the internal charger circuitry, and into the battery. And some losses in the battery itself. Is the 14-50 plug 100' away from the electrical panel using 6 AWG wiring?

Any more is probably just normal variability in your home usage.

 

[18_Mdl_P3D]

I believe the battery efficiency for the Mdl 3 extd range pack is 88%. This would account for some of the difference, the remainder is probably due to ~500-1000W constant draw. Leave the car unplug for a few days (phantom drain); there will be ~2-3% drop in the pack's charge over those 3 days. All cars draw power off their battery, even ICE cars. An ICE car's battery will be dead in about a month if never used. All the computer systems are the reason for the constant draw. So think of having your home computer on all the time...that's where the increase is probably coming from.

 

[joosh]

If the car is plugged in but not charging it will draw from the charger to power the car when you turn it on. Like if you're sitting in the car playing with the display or the car is updating. If the battery heater has to run in really cold weather that's power that is used without going into the battery first.

Maybe 10%-20% losses just getting the energy into the battery, especially when it's making the run all the way from your house power meter, through the Tesla connector, into the car, through the internal charger circuitry, and into the battery. And some losses in the battery itself. Is the 14-50 plug 100' away from the electrical panel using 6 AWG wiring?

Any more is probably just normal variability in your home usage.

Heating the battery makes sense if that's where the extra consumption is coming from.
My 14-50 plug is actually < 25' from my panel. I'll be installing the wall charger in it's place as soon as it comes in.

 

[derotam]

I am just two weeks into owning my M3 and have been charging to 80% at night on a schedule. I typically charge from 57% for a total of 23% charge which for a 75kw battery equates to ~18kw. I’ve noticed my daily kw avg consumption at home jump by at least 25kw per day since I started charging my M3 at home. We’re not doing anything different at home energy wise and I understand that’s a big variable, but I’m wondering if my M3 is using power from the plug while waiting to charge on its schedule? My garage right now is averaging 50 degrees F at night. Just trying to figure out where the 25kw is coming from when it should be around 18kw. Any thoughts?

I see a lot of people looking at their average home usage numbers and while that MAY give you some information, it should not be used as a reliable source. It is best to actually look at the usage on the car charging circuit to see what it actually is doing.

Pre-heating the car is going to use power. Also, since you are charging on a schedule, if the battery cools too much on cold nights before it starts charging then some power is going to be used for heating the battery.

 

[Silicon Desert]

Heating the battery makes sense if that's where the extra consumption is coming from.
My 14-50 plug is actually < 25' from my panel. I'll be installing the wall charger in it's place as soon as it comes in.

yes, but at an ambient temperature off 50 F, the battery heater should not be coming on at all. In my car up here in the cold winter, it doesn't seem to come on until under 40F in the garage. Even then, it doesn't stay on for long.