Battery Heater not coming on on Cold Mornings?

[WannabeOwner]

I can't seem to get the battery heater to come on in the morning. Temperature is around freezing, car is charged for at least an hour immediately before I depart and cabin heated for 15 - 30 minutes, but still I have almost zero Regen on setting off and don't get full regen for 30 minutes driving (so i figure the battery must have been cold enough for battery heater to be worth turning on). Range Mode is definitely off.

 

[chargeshare]

As I understand it the battery heater turns off when the battery reaches 8C. This is when you have ~30kW of regen.

 

[animorph]

If the battery level is 99% when you start driving you will have no regen. Roughly, there's nowhere for the energy to go with the battery full. I would also assume the battery charging taper would not appreciate 50kW to 70 kW charging the battery at 99% SOC.

 

[WannabeOwner]

As I understand it the battery heater turns off when the battery reaches 8C

Thanks, are there any tools that will let me see the Battery Temperature? AFAIK its not part of the API feed that I can see e.g. from TeslaFi. Seems to me that given the outside was 2C and the cabin 6.5C that battery should have been below 8C, car had been parked outside in the cold, overnight, for 14 hours

If the battery level is 99% when you start driving you will have no regen

Indeed, but full regen does not appear for 30 minutes.

I will test again on a shorter trip where I don't need 100% at start. My normal route gets me to highway speeds after less than 10 minutes local road driving, so (based on data for a different recent longish drive) 30 minutes out I'd gone 35 miles and battery down from 97% to 80% and I specifically remember that full-Regen became available 30 minutes into that particular trip.

What I don't understand is why battery heater doesn't come on (neither during charging nor during initial driving)

 

[WannabeOwner]

OK, made a hopefully more useful test last night. Cold here at the moment ...

Connected and Car's TOU Scheduled Charging came on at 1AM.

TeslaFi logs show that the car charged from 01:08 to 04:09. Battery heater did not come on at all.

External temperature was -4.0C initially falling to -4.5C. Internal temperature was +4.4C falling to +3.0C

Climate came on (scheduled) at 05:40, external temperature -4.0C, internal temperature climbed from 3.5C to 27.1C over 15 minutes, clime was on for 30 minutes. Battery heater did not come on.

Is this "normal and as expected" or do I need to contact Service and ask them to check it out?

I had a similar situation on an almost-as-cold night a week or two back, and had Regen was 50% for 15 minutes and then 75% for a further 5-10 minutes before I got full regen. My expectation is that with Charging and Climate on and cold outside I ought to get Battery Heater on too?

(Snow lying on the ground here this morning, so car has stayed home rather than driving to work)

 

[Veritas1980]

OK, made a hopefully more useful test last night. Cold here at the moment ...

Connected and Car's TOU Scheduled Charging came on at 1AM.

TeslaFi logs show that the car charged from 01:08 to 04:09. Battery heater did not come on at all.

External temperature was -4.0C initially falling to -4.5C. Internal temperature was +4.4C falling to +3.0C

Climate came on (scheduled) at 05:40, external temperature -4.0C, internal temperature climbed from 3.5C to 27.1C over 15 minutes, clime was on for 30 minutes. Battery heater did not come on.

How much regen did you have when you left?

I don't think the battery heater comes on when you are charging, unless the pack is so cold soaked that it can't charge.

But in your case, I assume that the charging will heat up the pack and there is no need for the battery heater to turn on together with the scheduled preheating.

As previously stated by chargeshare, the battery preheating will only give you around 30 kW regen, not full.

 

[WannabeOwner]

As previously stated by chargeshare, the battery preheating will only give you around 30 kW regen, not full

Ah, I missed that, thanks. Although with battery heater not coming on I guess its moot

Sadly I didn't have to drive this morning, but previously when weather cold, battery NOT charged above 90%, I typically get 50% regen for 15 minutes, and then 75% regen for the next 5 - 10 minutes, and then 100%

From various threads I have read (albeit not entirely 100% clear ...) it seemed that, on cold days, a battery charge for, say, 2 hours and climate on for, say, 30 minutes, both immediately before departure, would warm the battery enough for no?? regen limit?

if I am mistaken on that, and what I am seeing is normal, then I'll stop wondering if my car has some CONFIG discrepancy or similar.

I could turn on MAX POWER (i.e. as if for Launch) as an experiment?

 

[Veritas1980]

Ah, I missed that, thanks. Although with battery heater not coming on I guess its moot

Sadly I didn't have to drive this morning, but previously when weather cold, battery NOT charged above 90%, I typically get 50% regen for 15 minutes, and then 75% regen for the next 5 - 10 minutes, and then 100%

From various threads I have read (albeit not entirely 100% clear ...) it seemed that, on cold days, a battery charge for, say, 2 hours and climate on for, say, 30 minutes, both immediately before departure, would warm the battery enough for no?? regen limit?

I think that very much depends on how cold it is and with which rate you are charging with. In my garage we share the juice between 4 chargers, and normally I get to charge at 11 kW and I have no limit on regen after (ambient temp around 8-10°C), but if it is busy and I charge with 4-5 kW i may have a bit of limit for the first 10 min of driving.

I preheated my car on monday before leaving work. Outside temp around -4°, battery heater was on for around 15 min during preheating and for around 6 min while driving (data from Teslafi). It correlates fine with I had around 30 kW regen after driving for a bit.
I have 18 km drive home on motorway, and in winter, even with 30 min preheating, I always come home with limit on regen.

if I am mistaken on that, and what I am seeing is normal, then I'll stop wondering if my car has some CONFIG discrepancy or similar.

I could turn on MAX POWER (i.e. as if for Launch) as an experiment?

Tesla Björn did a video where he tested the MAX POWER theory, and it seems to work, however I guess you can't turn that on remotely or schedule it.

 

[WannabeOwner]

Outside temp around -4°, battery heater was on for around 15 min during preheating and for around 6 min while driving (data from Teslafi)

Thanks. I have never seen battery Heater shown as ON in TeslaFi. I've been waiting for this "cold for UK" weather to see if that would trigger it ...

Tesla Björn did a video where he tested the MAX POWER theory, and it seems to work, however I guess you can't turn that on remotely or schedule it.

I'll try it. Yes, cannot schedule, but I'd like to know if my Battery heater EVER comes on - because if not presumably something needs fixing

 

[Veritas1980]

I'll try it. Yes, cannot schedule, but I'd like to know if my Battery heater EVER comes on - because if not presumably something needs fixing

You could also schedule a quick preheating for maybe 10 minutes before charging at night to see if it kicks in. Of course not right after you've had a long drive.

 

[AWDtsla]

If the battery level is 99% when you start driving you will have no regen. Roughly, there's nowhere for the energy to go with the battery full. I would also assume the battery charging taper would not appreciate 50kW to 70 kW charging the battery at 99% SOC.

Common myth. If the pack is at 50C, you will have regen. Of course, it's nowhere near 50C.

 

[animorph]

Common myth. If the pack is at 50C, you will have regen. Of course, it's nowhere near 50C.

What part is myth? I always have no regen when I charge to 100%. Even if it's hot out, in Arizona.

Edited to add:

from my X manual:

"The amount of energy fed back to the Battery using regenerative braking can depend on the current state of the Battery and the charge level setting that you are using. For example, regenerative braking may be limited if the Battery is already fully charged or if the ambient temperature is too cold."

 

[AWDtsla]

What part is myth? I always have no regen when I charge to 100%. Even if it's hot out, in Arizona.

Edited to add:

from my X manual:

"The amount of energy fed back to the Battery using regenerative braking can depend on the current state of the Battery and the charge level setting that you are using. For example, regenerative braking may be limited if the Battery is already fully charged or if the ambient temperature is too cold."

The manual is wrong, since it has nothing to do with the ambient temp, but the internal temp of the pack

I've observed 50% regen after leaving a supercharger with a hot pack at 99%.

 

[WannabeOwner]

Well would you Adam and Eve it ... battery heater came on last night.

Car did not charge last night (didn't go out yesterday, 6" of lying snow and being British that means the country has ground to a halt ...)

I have TOU scheduled charge from 1AM but parasitic loss not enough. Scheduled Climate came on at 5:41 (External -5C, internal 0C) and a minute later Battery Heater was on (for 23 minutes). Charging then started after 12 minutes as battery had fallen a few percent below 90%

Decided to delay normal departure time, so put Climate back on at 6:43 (-5C, 9C) and Battery heater was back on within a minute ... (only stayed on for 5 minutes) (Charging had finished a minute or two earlier)

So I guess it just wasn't cold enough before ...

You could also schedule a quick preheating for maybe 10 minutes before charging at night to see if it kicks in.

That was the case in this test. Charging had not been on before Cabin Heating ... but seems that Cabin Heating was enough to trigger Battery Heater

However, one significant difference. Normally the car is not plugged in overnight (I charge at work) so perhaps that is needed for Battery Heater to come on (in my temperature / circumstances) in the morning?

Either that, or because car was parked yesterday it was properly cold-soaked for the first time given normal UK climate.

Battery heater came on yesterday morning too _ I was mistaken in my post yesterday, must have looked at the wrong data. Again that was 1 minute after Climate came on. Car had charged for 3 hours or so, but finished 1h30m before Climate came on, so battery was probably not cold soaked at that time.

 

[Veritas1980]

However, one significant difference. Normally the car is not plugged in overnight (I charge at work) so perhaps that is needed for Battery Heater to come on (in my temperature / circumstances) in the morning?

I did a test yesterday after our talk here, and battery heating for sure comes on with just the HVAC turned on and the car unplugged. I arrived at work around 7 a.m. in -11°C and a lot of snow and wind with a warm battery, no limit at all.

At 3.15 p.m. I turned on the preheating, outside temperature at that point at -7°C and windy, so very cold battery.

The battery heater turned off at 3.44 p.m. giving me around 30kW regen or what looks around 1/3 - 1/2 on the display. Preheating was on at 22°C while removing snow from the car until 4.16 p.m.
Minus the vampire drain during the day, I would estimate that it cost about 4 kWh for what was 1 hr of total preheating of cabin and battery in these conditions.