"Less energy is available due to cold battery" trying to charge

[rpo]

I've never had a L2 ramp that slow at low states of charge, and trust me I've been in that situation plenty. I've had pesky low states of charge when Supercharging but never while on L2 (this is a known bug, AFAIK). IMHO 29 amps were going to the battery heater, leaving virtually nothing to actually charge the car. Running the cabin heater would exasperate the issue. It reiterates my point that 30A L2 charging in cold climates is insufficient. One way to test this theory would be to cold soak the battery below 10% SoC, next to a 48A charger. I may try this sometime and report back.

I don't think the battery heater was running at all in the OP's case. He/she reported the car's power draw was at 1 amp but increased when the HVAC was turned on. I believe the car's reported power usage includes the battery heater as well.

 

[rypalmer]

I don't think the battery heater was running at all in the OP's case. He/she reported the car's power draw was at 1 amp but increased when the HVAC was turned on. I believe the car's reported power usage includes the battery heater as well.

I'm not so sure about this. You'd have to attach an energy monitor of sorts to the L2 charger, or use a L2 charger that measures current.

 

[MP3Mike]

I think he was reporting the draw the EVSE was reporting.

 

[Big Earl]

Was range mode on or off at the time of this incident?

 

[jsmay311]

So the Model S can use utility power to run the cabin heater but not the battery heater??? That is insane! (Almost as insane as the people trying to excuse this behavior as acceptable. Almost, but not quite.)

Separate from the battery heater issue: I find it curious that Tesla battery charging/regen is so much more negatively affected when the batteries are (even mildly) cold than other EVs. Does this have to do with Tesla using NCA cells when basically everyone else uses NMC?

 

[jsmay311]

For many new owners, they don't know that the the battery heater is the heat that is transferred into the Cabin. I believe they make the assumption that by turning on the heater, it only radiates a heater element near the console.

I've seen variations of this statement in lots of threads, stating (or implying) that the battery and cabin heating loops are tied together.

Does this have any basis in fact? Or is it just a myth based on a non-relevant diagram from a patent?

 

[MP3Mike]

I've seen variations of this statement in lots of threads, stating (or implying) that the battery and cabin heating loops are tied together.

Does this have any basis in fact? Or is it just a myth based on a non-relevant diagram from a patent?

It is a myth based on a patent. There are two separate heaters. A air heater in the cabin, and an immersion heater in the battery coolant loop. Heat does not move between the battery and the cabin.

 

[MP3Mike]

For many new owners, they don't know that the the battery heater is the heat that is transferred into the Cabin. I believe they make the assumption that by turning on the heater, it only radiates a heater element near the console.

And they would be correct.

 

[AWDtsla]

So the Model S can use utility power to run the cabin heater but not the battery heater??? That is insane!

Basically. Because Tesla threw some weird rules together about how this stuff turns on and called it software. They could have at least admitted their ignorance and given the user control over everything. This describes many things about the car, all the various heaters to the air suspension controls.

(Almost as insane as the people trying to excuse this behavior as acceptable. Almost, but not quite.)

These guys would drink the kool-aid on command. Welcome to the post truth world.

 

[Big Earl]

So the Model S can use utility power to run the cabin heater but not the battery heater??? That is insane! (Almost as insane as the people trying to excuse this behavior as acceptable. Almost, but not quite.)

Separate from the battery heater issue: I find it curious that Tesla battery charging/regen is so much more negatively affected when the batteries are (even mildly) cold than other EVs. Does this have to do with Tesla using NCA cells when basically everyone else uses NMC?

It will absolutely run the battery heater from shore power as long as range mode is off.

My Fiat 500e behaves similarly to the Tesla. It has to heat the battery to above freezing before it can be charged or provide any regen. The warmer it gets, the more regen is available.

 

[AWDtsla]

It will absolutely run the battery heater from shore power as long as range mode is off.

My Fiat 500e behaves similarly to the Tesla. It has to heat the battery to above freezing before it can be charged or provide any regen. The warmer it gets, the more regen is available.

There is a combination of SoC, available wall power, and temperature, where it will refuse to turn on.

 

[MP3Mike]

So the Model S can use utility power to run the cabin heater but not the battery heater??? That is insane!

It can, but in this situation it is programmed not to. I suspect this is a result of problems people had last year. They were at a low SoC with a cold soaked battery and they plugged into a "low-power" EVSE. The car turned the battery heater on, which took more power than the EVSE supplied and they actually ended up running the battery dead rather than charging the car. So they had a slightly warmer battery, but not warm enough to charge at full speed, and not enough charge remaining to continue to run the battery heater or drive somewhere else.

You can look at it a few ways:

1. The EVSE he was using was too low power.
2. Tesla put too big of a battery heater in the car.
3. Tesla put a fixed power battery heater in the car.

In the Model 3 Tesla solved #3 by making the motor/inverter the battery heater so they can control how much power they turn into heat.

From what I have seen the battery heater draws 6kW. The charger efficiency is around 90%, and there is ~0.5kW of other draw while charging. (Coolant pumps, screens, computers, etc.) So you need an EVSE that can provide at least 7.2kW to be able to run the battery heater. So if you have a 30A @ 240v EVSE you should be good. But if your EVSE is on commercial power you would need 35A @ 207v.

The OP said he was charging at 30A @ 240v, but his screen capture showed 214v. So there was only 6.4kW of power available. (He was very close to having enough power available.)

Of course only Tesla knows exactly what the parameters they use to determine if the battery heater can be run while charging or not. (They could have just set the limit to 35A, or it could be 40A. Or maybe they set it to 32A since that is what their Gen2 UMC provides.)

Someone should test it out with a Tesla WC. (But the only options it has to configure are for 28A, 32A, 36A, and 40A which I guess would be good enough.)

@yobigd20 What were the specs on the charger at the Holiday Inn? (Or was the screen capture from that one and not the one near the train station?)

 

[scaesare]

I thought that the battery heater was 5kW. He was plugged in to a 30A outlet, which even at 207 volts should be 6.2kW. So that shouldn't have been the problem. But I wonder if you are on the right track, maybe Tesla has the cut-off at a 40A connection before it will allow the battery heater to turn on when the pack is cold-soaked at a low SoC. It sure would be great if Tesla shared these kind of details.

I think this and the post from @rpo maybe part of this.

The battery heater part is labeled a 5.5KW part. In the operational description in the service manual, the cabin heater[1] is described as being able to be PWM controlled to operate at a lower power. The pack heater is not described this way. Power usage graphs seem to indicate it may be pulsed at a relatively slow rate (every few seconds) if the demand is for less than full-on.

Along with other system power draw (pumps, computers, etc...) I wonder if this is too close to the shore power source limit?

It would be interesting to see if this same behavior persists with a 40A shore connection.

[1] Which, as stated previously, indeed only heats cabin air... no coolant loop connection.

 

[AWDtsla]

It can, but in this situation it is programmed not to. I suspect this is a result of problems people had last year. They were at a low SoC with a cold soaked battery and they plugged into a "low-power" EVSE. The car turned the battery heater on, which took more power than the EVSE supplied and they actually ended up running the battery dead rather than charging the car. So they had a slightly warmer battery, but not warm enough to charge at full speed, and not enough charge remaining to continue to run the battery heater or drive somewhere else.

You can look at it a few ways:

1. The EVSE he was using was too low power.
2. Tesla put too big of a battery heater in the car.
3. Tesla put a fixed power battery heater in the car.

In the Model 3 Tesla solved #3 by making the motor/inverter the battery heater so they can control how much power they turn into heat.

From what I have seen the battery heater draws 6kW. The charger efficiency is around 90%, and there is ~0.5kW of other draw while charging. (Coolant pumps, screens, computers, etc.) So you need an EVSE that can provide at least 7.2kW to be able to run the battery heater. So if you have a 30A @ 240v EVSE you should be good. But if your EVSE is on commercial power you would need 35A @ 207v.

The OP said he was charging at 30A @ 240v, but his screen capture showed 214v. So there was only 6.4kW of power available. (He was very close to having enough power available.)

Of course only Tesla knows exactly what the parameters they use to determine if the battery heater can be run while charging or not. (They could have just set the limit to 35A, or it could be 40A. Or maybe they set it to 32A since that is what their Gen2 UMC provides.)

Someone should test it out with a Tesla WC. (But the only options it has to configure are for 28A, 32A, 36A, and 40A which I guess would be good enough.)

@yobigd20 What were the specs on the charger at the Holiday Inn? (Or was the screen capture from that one and not the one near the train station?)

Lots of corrections here.

5.5kw @ 450V. At near 0% SoC, your pack voltage is somewhere in the low 300's probably. So more like more like <4kW in this state. 30A @ 200V is plenty to power it.

Also it doesn't matter if the heater power exceeds the charger power. What matters is if there's enough energy left in the pack to affect the charging rate meaningfully. They don't calculate anything like this. In fact, in an exercise of pure frustration - they disable the ability of a P owner to turn on the batter heater under 20%. So it doesn't matter that I know I'm going to arrive at the supercharger with 8-10% battery left, I can no longer heat the pack so I can charge quickly.

 

[jsmay311]

You can look at it a few ways:

1. The EVSE he was using was too low power.
2. Tesla put too big of a battery heater in the car.
3. Tesla put a fixed power battery heater in the car.

Is #3 a definitively-known thing? (Edit: I see in scaesare's post that this is based on a description in the manual and observations of power draw. Seems pretty legit.)

I find it kinda surprising that it wouldn't have a controller to modulate the heater. But then again, lots about how Tesla does things surprises me.

It's also very surprising/discouraging that Tesla would have such a glaring system design flaw in such a mature product. Can't blame this on early product lifecycle growing pains like you can with all the Model 3 issues and unfinished software.

 

[Graffi]

Lots of technical discussion here, which is wonderful, but back to the OP issue.

He parked the car for long enough time for the battery to cold soak at a very low battery level. The solution for lessons learned is to NEVER park the car with very low battery in very cold weather. If he had Supercharged the car prior to parking the battery would have been warm, and would have accepted a high level of charge at a fast speed. Then when he left with a cold a cold battery the drive would cause the battery to warm up so by the time he got to the Supercharger it would have accepted full rate charge. jmho

 

[cmaster]

When did they changed it?

And they would be correct.

 

[MP3Mike]

When did they changed it?

View attachment 280125

They haven't. That graphic doesn't show the cabin and powertrain loops being connected. (However, they do share some portions of the AC system.)

(You will notice that the battery heater is in the coolant loop and the "air PTC" is in the cabin in the HVAC section.)

 

[rypalmer]

View attachment 280125

Damn, I wish I had access to this screen while driving. So much good info.

 

[Big Earl]

They haven't. That graphic doesn't show the cabin and powertrain loops being connected. (However, they do share some portions of the AC system.)

(You will notice that the battery heater is in the coolant loop and the "air PTC" is in the cabin in the HVAC section.)

The box that displays "parallel" can switch to "series," connecting the two loops together for heating. The valve that's shown below "chiller" is for cooling the battery.