Explain battery drain and Snowflake

[Jager]

Is this via service menu or some other tool (I'm curious to look at mine)?

I use Scan My Tesla, in conjunction with an OBD wireless adapter, to read data directly off the CanBus in my Model 3.

The only way I know to currently get pack temps in the CT is via Tessie, using its "Direct Telemetry" option.

I much prefer Scan My Tesla (and hope that it, or something similar comes to the CT) because it is far more granular, has a vastly higher sample rate, and gives you access to a raft of other data other than thermals.

The Tessie app works pretty well, considering how limited the data is. I'll use it until something better comes along.

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[docowen]

Along the same line, I have noticed my truck , at times, with outside temp around 10 F has a really hard time taking charge from 32A mobile connector plugged into a 240 outlet. Sometimes it continually says "warming battery" in the app and never really adds much charge. I have noticed that if I plug into a destination charger (still says only 32A) but does better and will actually get to where it takes a charge. It does worry me though if I ever get to the ski area and all the desination chargers are full. I'm going to email the area as there are lots of EV's coming up to the mountain these days and it is harder and harder to find open chargers.

 

[Kryptek]

Along the same line, I have noticed my truck , at times, with outside temp around 10 F has a really hard time taking charge from 32A mobile connector plugged into a 240 outlet. Sometimes it continually says "warming battery" in the app and never really adds much charge. I have noticed that if I plug into a destination charger (still says only 32A) but does better and will actually get to where it takes a charge. It does worry me though if I ever get to the ski area and all the desination chargers are full. I'm going to email the area as there are lots of EV's coming up to the mountain these days and it is harder and harder to find open chargers.

Portable propane/diesel heater + thermal car cover in emergency road side gear!

 

[Crissa]

Along the same line, I have noticed my truck , at times, with outside temp around 10 F has a really hard time taking charge from 32A mobile connector plugged into a 240 outlet. Sometimes it continually says "warming battery" in the app and never really adds much charge. I have noticed that if I plug into a destination charger (still says only 32A) but does better and will actually get to where it takes a charge. It does worry me though if I ever get to the ski area and all the desination chargers are full. I'm going to email the area as there are lots of EV's coming up to the mountain these days and it is harder and harder to find open chargers.

Yeah, as you go down below freezing, the cells have trouble accepting a charge. It's best to make sure either you have sufficient power, or that you pre-condition the pack and charge it before letting it sit in the cold.

My Zero can't even charge at 10F.

I'd think that 7kW would be sufficient to heat and charge the pack! But it is a pretty big thermal mass.

-Crissa

 

[Jack27]

Ok battery drain means you’re super tired and need a yaga bomb and snowflake means you a little light in the loafers if ya know what I mean

 

[Jack27]

Thats huge..

Exactly was she said !

 

[mongo]

Yeah, as you go down below freezing, the cells have trouble accepting a charge. It's best to make sure either you have sufficient power, or that you pre-condition the pack and charge it before letting it sit in the cold.

My Zero can't even charge at 10F.

I'd think that 7kW would be sufficient to heat and charge the pack! But it is a pretty big thermal mass.

-Crissa

Indeed, the original Tesla patent https://patents.google.com/patent/US20190070924A1/en calls out 85Wh/C (probably the Y pack)
7kW would get you 82C per hour (assuming COP of 1 and no heat loss)

Trying to charge frozen cells can result in lithium plating which results in irreversible capacity loss.

 

[Outdoors]

Yeah, as you go down below freezing, the cells have trouble accepting a charge. It's best to make sure either you have sufficient power, or that you pre-condition the pack and charge it before letting it sit in the cold.
-Crissa

Better to charge post drive then let cars sit/cool and charge at night if it is super cold. Pack cools, and then charging at low amps will eventually go into warming mode. Garaged VRBO and AirBnB work for me even at low charge rates as long as other items aren't on the same circuit. I usually have enough to get me to the top of the ski hill, and get some on the way back down. I only need about 35 miles a day. Yet I am always charging if not driving.

Many are used to hey lets get cheap power at night. In extreme cold, and while traveling kind of have to reverse the thought if not using or have access to full amps.

Also tires. Don't forget those. They can be lead weights if underinflated. Wake up to a 30 degree temp change. Don't just charge. Inflate.

 

[Crissa]

Better to charge post drive then let cars sit/cool and charge at night if it is super cold. Pack cools, and then charging at low amps will eventually go into warming mode.

And this only applies to freezing weather! Even if you do put it in a warm garage, it can take hours for that warmth to get into a cold pack.

And a trickle is better than none, as it can be used to keep the pack ready for use in the morning.

But it's not dangerous for your pack to get cold - you just can't use it efficiently if it's cold. Unlike older batteries, a lithium battery will be fine once it warms back up, it won't even have lost much charge!

-Crissa

 

[AlmostHuman]

I think this icon is a carryover from the power display on some of the first models. For example our X the way it displays regen or power being delivered is with an energy graph that is round. When regen is limited it is represented with dashes in the bottom of the regen graph. It is a little difficult to see but the power meter on the Cybertruck (other models that have the meter as well) will also so dashed lines when regen is limited (would be at the red arrow in the below pic) I assume they added the green icon to make it more apparent so people are more careful. Once you get use to the distance needed to stop with only regen as soon as that is reduced it can surprise you that physical brakes are needed for the same stop you have made hundreds of times with only regen.

Model X energy graph:

Cybertruck power meter:

Like this

 

[AlmostHuman]

Was thinking that for those of you that want the snowflake to go away just set a Supercharger as your destination even if you are not going there. It will warm the battery fast and likely remove that snowflake in less than 10 minutes, my guess.

 

[mongo]

Was thinking that for those of you that want the snowflake to go away just set a Supercharger as your destination even if you are not going there. It will warm the battery fast and likely remove that snowflake in less than 10 minutes, my guess.

Yep, it does (and drains a few % from the pack).

 

[eswimm]

I expect Tesla is just being very cautious.

One thing I noticed from the teardown, is that there's a lot of air space (above the retardant foam) on the cells. It makes me wonder if the CT battery gets less warming from the cabin. Add to that the snowflake threshold of <65F and it's no surprise that people are seeing the snowflake stick around for hours of driving. I wonder if Tesla is letting too much heat out via the heat exchanger or into the cabin via the heat pump.

I'm pretty shocked by the efficiency of the CT (mine's about 385 Wh/mi over 4000mi) vs my 2016 Model X P100D (379 Wh/mi over 55k miles). The difference in weight, rotational mass of the tires (I had 20s on my X) and the lower efficiency of AT tires, has me amazed at the efficiency of the CT. I'm really not sure if the CT simple doesn't produce enough waste heat to keep both the cabin and battery above temp or if Tesla simple hasn't tuned the cooling system to keep as much heat as possible in cold weather.

 

[mongo]

One thing I noticed from the teardown, is that there's a lot of air space (above the retardant foam) on the cells. It makes me wonder if the CT battery gets less warming from the cabin. Add to that the snowflake threshold of <65F and it's no surprise that people are seeing the snowflake stick around for hours of driving. I wonder if Tesla is letting too much heat out via the heat exchanger or into the cabin via the heat pump.

I'm pretty shocked by the efficiency of the CT (mine's about 385 Wh/mi over 4000mi) vs my 2016 Model X P100D (379 Wh/mi over 55k miles). The difference in weight, rotational mass of the tires (I had 20s on my X) and the lower efficiency of AT tires, has me amazed at the efficiency of the CT. I'm really not sure if the CT simple doesn't produce enough waste heat to keep both the cabin and battery above temp or if Tesla simple hasn't tuned the cooling system to keep as much heat as possible in cold weather.

The tear downs I've seen have the pack upside down. That air space is on the bottom which is an improvement in ambient isolation.
The cabin floor of the Cybertruck and Y is a layer of high density foam, so fairly insulative on its own. X/S/3 are metal floor then metal pack.

Munro & Co. have begun their teardown of the Cybertruck battery.

Interestingly, there is a lot of space above the cells. It doesn't appear to be enough for another layer, but it is a curious amount of emptiness. Is it needed for cooling? Could the originally-planned double-stacked pack be achieved with an only slightly taller pack?

 

[eswimm]

The tear downs I've seen have the pack upside down. That air space is on the bottom which is an improvement in ambient isolation.
The cabin floor of the Cybertruck and Y is a layer of high density foam, so fairly insulative on its own. X/S/3 are metal floor then metal pack.

Interesting, I didn't realize the pack was upside down.

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