Battery life and cold weather

[Rio]

With the recent spell of cold weather we are getting here in the prairie province of Alberta I am wondering about how the cyber truck battery performance would be affected. Today we reached approx. -40 ‘C which is equivalent to -40’f.
Cold is an understatement. Many people would state your best course forward is to move where human life is possible, but I’m stuck here. I would hate to be stuck out somewhere in this weather with the batteries quickly draining. Does anyone have any insight into temperatures effect on battery life?

Advertisement

 

[Saskateam]

Going with the biggest battery you can get for the prairie provinces is best. If possible park inside to reduce the loss from heating batteries. Preheat while plugged in if possible to reduce battery usage. The battery is still going to get hit in this weather.

 

[ajdelange]

In general the colder a system is the slower all chemical reactions and as a car spends most of its time in storage (unless it's a taxi) I guess we might conclude that the battery in a BEV in a cold climate will last longer than one used in a warm climate. This assumes that when the vehicle is actually being operated the battery is at proper temperature or is at least being operated properly for its actual temperature. Tesla has developed a sophisticated battery management system to see to this. In answering thus I am assuming by "battery life" you mean the number of years the battery will last.

Now if when asking about battery life you want to know how long a charge lasts the answer is quite different. When the weather is very cold several things happen that drain the battery faster than when the weather is warmer. The most dominant of these is that you use the heater. In an ICE vehicle the heater uses heat that is being wasted any way and there is no penalty. In a BEV heating uses energy that could be used to move the car and is, thus, from the perspective of miles driven, wasted. How much you waste on heating depends, obviously, on how cold it is and on how you use the heater. If the cold is moderate many people don't use the heater at all relying instead on the seat heaters for comfort. I am able to do this and thus find my winter and summer range per kWh essentially identical. But -40 °C (or, if you prefer, - 40 °F) is not by anyone's reckoning moderately cold and you may find a substantial loss of battery energy to cabin heat.

Assuming that the cabin of the CT is about the size of the cabin of an X and that the CT's traction consumption will be about 167% of an X's the amount of heat required to keep the cabin warm will be about the same and the range reduction about 2/3 of what you would see in an X. So if you can find out what the range reduction is for an X in your region you might get a stab at what to expect with the truck.

Another factor is that air becomes denser when it is cold thus meaning more drag. Down to freezing the additional drag may represent A 10% increase. Down to -40 it's going to be more than that. Lubricants are stiffer at colder temperatures so there will be some additional losses in the differentials. As they warm with driving that will go down but for short trips could make a noticeable difference.

 

[Rio]

Thanks guys for you informative reply’s. I would love to see Tesla come out with a dual motor with 500 mile range battery. I wonder if when parked outside if a standard plug in would be enough in this cold to keep the batteries topped up.

 

[ajdelange]

There was a Youtube video posted on this subject a while back in which someone did this experiment with a S. The answer was "No." Don't remember any details.

 

[Saskateam]

Once the battery is warm it will radiate heat through the cabin floor and help with heat. I think I will be using my heated jacket when it is this cold to help with the heat issue on short drives. Can’t be as cold as my 95 Jeep YJ with the soft top on and the jacket helps with driving it in this weather. Definitely going to need to charge more in this weather. I am hoping the CT will help heat the garage when it is charging.

 

[ajdelange]

Driving at a constant 60 mph with consumption at .5 kWh/mi implies 30 kWh per hour meaning power is being drawn from the battery at 30 kW. Overall efficiency of 90% would mean 3 kW of waste heat which is equivalent 10.2 BTU/h, i.e. 5/6 a ton of heating. That ought to be enough to keep the relatively small volume of the cabin warm as 4 tons is enough to keep my house warm. But my house is not subject to a 60 mph wind at -40 °F! So yes, capturing the waste heat and using it to heat the cabin is a good idea but we wouldn't want it coming through the cabin floor as that would burden the A/C in the summer. Most of the waste heat will be generated in the inverters and motors and relatively little in the battery so that, in fact, under some conditions you may have to heat the battery as opposed to relying on it as a source of heat. The heating/cooling system needs to capture the waste heat from the motors and inverters and transfer it to the battery and cabin in winter and dump it overboard in the summer along with heat that it collects from the cabin and battery which needs to be cooled in hot weather. The heating/cooling system has gotten more sophisticated as Tesla has gained experience with it. For example, the X and S have a separate electrical heater to warm the battery. It is rumored that the 3 can operates the transistors in the inverters to make them less efficient thus producing more waste heat which, as the inverters and battery are on the same coolant loop, gets transferred to the battery. Tesla has filed patents for systems with a bewildering array of compressors, evaporators, condensers, heat exchangers, pumps. computer operated valves, radiators and sensors and. more recently, for a battery pack in which the cells are bathed in a circulating dielectric coolant. What winds up in the CT remains to be seen. They have a couple of years to refine the system even further.

 

[Saskateam]

I watched a video of a person camping in their M3 for 24 hours at -10 to -20c. They had just finished supercharging and the battery was still warm. The heat in the battery reduced the amount of heat the M3 needed to generate for around 12 hours. Be interesting to see how the CT handles heating. I wonder if it will use heat pumps in the HVAC system.

 

[ajdelange]

On heating the garage: The latest production cars charge at 11.5 kW and the charging is a little more than 90% efficient so there will be about 1100 W waste heat if the CT has the same charging capacity as the current cars. Only a couple of watts will be generated in the HPWC and cable. The rest will be released in the on board charging unit where, as is the case with the inverters, it will be collected by the cooling system and, in cold weather, transferred to the battery. Of that some will, of course, eventually make it out into the garage but precious little. In warm weather this heat will be dumped into the garage.

Battery charging rate must be limited when the battery is cold and so regenerative braking is limited when the car is parked outside or in a cold garage in the cooler seasons. Note that a software update in September raised the temperature at which this limiting at 60 °F. A strategy used for getting regen going ASAP is to schedule at home charging so that it finishes close to the time you intend to leave for the day. This relies on this rectfier waste heat to warm the battery,

 

[Saskateam]

https://apple.news/AjqAyo_ovTymHbkw-JjNTyQ
It is cold up here. The picture is the current temperature where I live in Saskatchewan.

 

[Saskateam]

WTFORECAST has it right today. Maybe we will drive the kids to school today instead of making them walk.

 

[Saskateam]

In this weather negligible amount of heat can be huge. Small amount of radiated heat can be the difference in feeling comfortable. I will take what I can get for heat.

 

[ajdelange]

Be interesting to see how the CT handles heating.

It certainly will - not that Tesla will reveal much.

I wonder if it will use heat pumps in the HVAC system.

In the broadest sense of the term a heat pump is a device that moves heat from a source at one temperature to a sink at a higher temperature and in this sense an ordinary room air conditioner is a heat pump. The CT will absolutely have that of course. People tend to think of a heat pump as a device that extracts heat from outdoor cold air and moves it into a warmer house. It takes energy to do this (2nd law) and it makes sense to use this technology if one kW of electricity can move enough heat. It's intuitively pleasing that the further uphill you have to push the heat the more power you require to push it and the less efficient the heat pump becomes. As an example, the heat pump in my house can suck about 3 kW of heat out of 50 °F ground water for each kW of electricity used to run the compressor. Thus the system delivers 4 kW of heat (the power that goes to the compressor gets converted to heat too) while drawing 1 kW and is said to have a Coefficient of Performance of 4. COP drops as the temperature difference gets larger. Modern air to air heat pumps will still produce enough heat to make them usable when outside air temperatures are a little below freezing but the COPs aren't very impressive and below that they are effectively electric heaters. In a system where you are trying to scrounge every watt you can and the air is a source of watts which can be grabbed with COP better than 1 a heat pump makes sense if other engineering considerations don't preclude their use so I think it quite probable that the CT will have one. But they will not be of much use once the temperatures go below freezing.

 

[VolklKatana]

With the recent spell of cold weather we are getting here in the prairie province of Alberta I am wondering about how the cyber truck battery performance would be affected. Today we reached approx. -40 ‘C which is equivalent to -40’f.
Cold is an understatement. Many people would state your best course forward is to move where human life is possible, but I’m stuck here. I would hate to be stuck out somewhere in this weather with the batteries quickly draining. Does anyone have any insight into temperatures effect on battery life?

Might take a look at this post from a model 3 user on their experiences, both good and bad:
https://www.reddit.com/r/teslamotors/comments/epfrp7/tesla_model_3_in_extreme_winter/