Noticed battery warming just plugged in not charging.

[Stretch2727]

I noticed a few days ago with the car only plugged in while checking on the app the snowflake disappeared and there were 10 more miles of range. It was about 10F outside and the car was set to time charge in the early morning in about 5 hours. I have a Juicebox charger on wifi where I can see the voltages and amperage and noticed the car was drawing about 10amps @240 volts during this time. Normally it is set to charge at 40 amps. No charging was indicated. After about 30 minutes the current draw from the charger stopped, the snowflake was gone, the blue bar was gone and there were about 10 more miles on the car mainly due to the blue bar now being green. I went to sleep so not sure if it cycled on and off.

I did the same thing the next night on my other model 3 and similar results.

So it appears to me the car was actively warming the battery by being plugged in but not charging. Both cars have 2018.50.6. I have not noticed this behavior prior but this was our first really cold spell. (For NJ!). I know the car does not have a direct battery heater, it was not charging so where was the current going? My suspicions are the current was going to motor using the "zero torque mode" to heat the battery coolant.

Anyone else see this behavior?

If so it is good to know you can heat the battery with just plugging in. I don't charge every night but could plug in to avoid the snowflake and very limited regen in the morning.



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[brianhill33]

I have a LR RWD and MR RWD, charging with a Juicebox 40, and both exhibit exactly that which you describe. IMO it’s operating as intended.

 

[Tozz]

The car has a battery heater, just not the same as with an S or X. You are correct it uses the "zero torque feature" of the motor. But in the end it boils down to the same: To warm up the coolant, that flows through the battery to warm up the pack.

My guess is that you have enabled scheduled heating. With that option on it learns your schedule (time you go to work in the morning, etc) and preheats the car for you so its ready when you depart.

I don't use this feature, but from what I've heard it's ability to learn your schedule isn't very good.

And yes, when you activate the "preheat" it uses shore power if that is available.

 

[Needsdecaf]

Scheduled heating of the pack?

 

[Tozz]

Scheduled heating of the pack?

The interior pre-heating option will automatically start pack heating if temperatures are cold enough (below freezing)

 

[rrolsbe]

Well maybe things have changed, but here is my understanding regarding active battery heating. The only time the battery will be heated, using the drive motor, is when the car is actively charging or the temperature is well below 0F something like -22F. Of course, the traction battery is also heated while driving. If the the battery is heated while pre-heating the cabin, I believe that would be new? The motor does make noise while it is actively heating just listen at the back of car and you will also hear the coolant pump at the front of the car. My 3 actively heats the battery while charging at temps at/below around 47F.

 

[rbaley]

Well maybe things have changed, but here is my understanding regarding active battery heating. The only time the battery will be heated, using the drive motor, is when the car is actively charging or the temperature is well below 0F something like -22F. Of course, the traction battery is also heated while driving. If the the battery is heated while pre-heating the cabin, I believe that would be new? The motor does make noise while it is actively heating just listen at the back of car and you will also hear the coolant pump at the front of the car. My 3 actively heats the battery while charging at temps at/below around 47F.

Ca

 

[rbaley]

The interior pre-heating option will automatically start pack heating if temperatures are cold enough (below freezing)

I agree with Tozz. Preheating the cabin after being at work for 10 hours, unplugged, with temps between -10 and 0F, resulted in both the snowflake and blue line disappearing after about 30 minutes in Chicago

 

[mrkymarc]

I noticed this behavior today as well. Temps were right around zero. Plugged into a 30amp source that usually maxes out at around 200volts. Battery still had the blue bar. Car only pulled 12 amps at 200v for several minutes. Seems to indicate the peak battery heating power is about 2500 watts.

 

[Stretch2727]

I did not have the cabin heating on in both instances. I remember double checking this as I thought I accidentally turned on and hence the current draw. Last night it was about 24F and it did not heat the battery prior to the timed charge but still had a snowflake and some blue bar. Tomorrow we will be close to 0F and I will see if it does this again. Would be good to know the threshold that it activates.

I noticed this behavior today as well. Temps were right around zero. Plugged into a 30amp source that usually maxes out at around 200volts. Battery still had the blue bar. Car only pulled 12 amps at 200v for several minutes. Seems to indicate the peak battery heating power is about 2500 watts.

Yes same level I was seeing. 10.6A @ 240 volts so about 2500 watts.

 

[Big Earl]

If it's quiet, you can hear the car doing battery heating. You can hear the pumps run and a faint whine as the motor consumes power while plugged in and not moving.

 

[Big Earl]

I managed to get screen shots from my Juicebox Pro 40 and the car last night while it was plugged in, heating the battery and not charging. I plugged in around 9pm and set the charge timer for 9:30pm. The car pulled 2.5 kW continuous while it was waiting for the charge timer and it heated the battery up enough to make the snowflake disappear and add 2% state of charge.

Pictures: https://photos.app.goo.gl/Rry5h4ERiVdgtDzc8

 

[derotam]

I managed to get screen shots from my Juicebox Pro 40 and the car last night while it was plugged in, heating the battery and not charging. I plugged in around 9pm and set the charge timer for 9:30pm. The car pulled 2.5 kW continuous while it was waiting for the charge timer and it heated the battery up enough to make the snowflake disappear and add 2% state of charge.

Pictures: https://photos.app.goo.gl/Rry5h4ERiVdgtDzc8

Nice info....as I narrow in on where you live based on info in pics...haha

 

[Big Earl]

Nice info....as I narrow in on where you live based on info in pics...haha

It isn't too hard to find me on PlugShare.

 

[AlanSubie4Life]

I’m surprised it is only 2.5kW. If track mode works, the cooling system must be capable of removing more heat from the motors than 2.5kW continuous...especially when it is really cold...

Maybe Tesla is conservatively working their way up to adequate battery heating. I would think they could get 10kW of heat out of these motors if they really put their heart into it.

 

[Big Earl]

It's possible that the level of heating increases as ambient temperatures get lower. I recall reading somewhere that the system is capable of producing up to 4 kW of battery heat. Unfortunately, I can't find that reference right now.

 

[StealthP3D]

Car only pulled 12 amps at 200v for several minutes. Seems to indicate the peak battery heating power is about 2500 watts.

One measurement under one environmental condition cannot possibly tell you what the system's maximum capacity (to produce heat) is. I'm sure it's a lot higher than 2500 watts! These cars are smart. It's almost like they are alive!

When we get "pet mode" and your car can follow you around like a puppy, the transformation will be complete!

 

[Kant.Ing]

I believe the working condition of electronics and silicon chips has to be above -40C, and these smart cars know that. As temperature approaches the dead zone, these cars will do whatever they can do to survive and maintain the heartbeats.

 

[3TRAY]

I had an idea that seems like it worked to pre-warm my battery.

Many people plug their car in to charge over night and the car finishes charging sometime in the middle of the night, then the battery cools down for hours. Many people have asked for a mobile app feature to be able to schedule the END time of charging so the battery is warm when you get in the car, but that's not available yet.

So my idea is this: Plug you car in at night and have your charge limit set to your normal 70%-80%. When you wake up in the morning, it's charged to that level but the battery has cooled down. At about 35-45 minutes before you're ready to leave the house on a cold morning, use the mobile app to increase the charge level by another 10%. The car begins charging again and by charging for another 30 minutes or so, it warms the battery quite nicely. Also, by doing this on cold mornings, your battery won't remain at a high SoC level for long, so no need to be concerned about keeping the battery overly charged.

I tried it this morning and it seemed to work well. There was still some dotted line visible on the left side of the regen/discharge bar, but not nearly as much as the other recent cold mornings we've had. When I got in the car, I put the charge level back to my normal setting.

Yeah, it takes a little manual work to make the adjustment 35 mins before leaving the house, then setting the charge level back to normal when you get in the car. But I think it worked out pretty well and I will try to remember to do this on these cold mornings.

 

[StealthP3D]

So my idea is this: Plug you car in at night and have your charge limit set to your normal 70%-80%. When you wake up in the morning, it's charged to that level but the battery has cooled down. At about 35-45 minutes before you're ready to leave the house on a cold morning, use the mobile app to increase the charge level by another 10%. The car begins charging again and by charging for another 30 minutes or so, it warms the battery quite nicely. Also, by doing this on cold mornings, your battery won't remain at a high SoC level for long, so no need to be concerned about keeping the battery overly charged.

A lot of people have suggested that but it's not optimal for battery life. The battery can supply current just fine when it's quite cold, it's the charging that degrades a cold battery. That's why regen is limited with a cold battery.

So, the best time to charge is when the battery is already warm from driving, like when you get home or early evening. By doing a second charge after the battery has cooled is inefficient and causes it to charge near the acceptable threshold of charging temperatures. It's not ideal.