Precondition car plugged in vs not plugged in

[Zimo]

I also was concerned about range degradation and scheduled an appointment to have the batteries checked. Here is the response I got from the service center.

On Nov 10, 2020, at 12:38 PM, Katie Mulock <[email protected]> wrote:

Hello,

This is Katie, from Tesla Rocklin. We have ran a battery health check on your vehicle, and found no faults with the cells; they are all charging to the proper voltage.


We have found that in cases where the battery is consistently charged to a lower state of charge, between 60-80% capacities, estimation becomes less accurate and tends to underestimate the true capacity of the battery. The result is an incorrect reduction in the displayed range estimate.


This does not affect the true range of the vehicle, as the end-of-drive conditions are based on real-time battery measurements of reducing battery power, rather than software estimates.


We recognize the inconvenience, and negative user experience associated with this range estimate. We are developing more accurate estimation algorithms which will be pushed over the air to the car when available.


Here is a great article regarding a Model 3 that was able to get more than the EPA rating/ what was displayed by adjusting their speed. Tesla Model 3 travels 606 miles on a single charge in new hypermiling record - Electrek


A good practice is to keep the consumption screen visible for true predicted range and monitoring driving habits and environmental conditions.

 

[mswlogo]

I have had my M3 plugged in and sitting for two months so far, in temps as low as -10 and it does wake up and charge a bit every day. Local mobile service guy said better to leave it plugged in and keeping battery up and allowing updates to load than to unplug the battery and store it inside. Indoor storage at hometown has no outlets available and they will not install any, just to show me how lousy customer service is in America in 2021.

I sure hope I have FSD complete when we get home in April.

I’d do the same. Completely different situation than preheating for your daily commute.

I would hope you don’t have it set to 90%. I’d probably set it to 60% if leaving it for months.

 

[Stv1der]

You're making a very strong claim Tesla has never made when all the evidence points to it being for comfort/feel reasons, especially since this was a frequent feature request (the cars did not originally do this! They added this at the end of winter last year IIRC).

Using Wiki articles or other publicly discoverable information on general Li-ion battery health recommendations doesn't lead you to the same behaviour Tesla does. For example, it normally lets the battery float around 35C passively if it can, choosing not to actively cool it. That's definitely hotter than that 25C number.

Further, they do some things as a trade-off. Charging at hot temperatures isn't normally good for battery health (you'll note most chargers for phones, tools, etc. don't allow charging when hot, even other EVs), yet Tesla actively heats the battery for Supercharging. This isn't "healthier" - the benefit they're getting from this is faster charging. The health would be better by not actively heating it so much and charging slower. Keep in mind the preheat temps range from about 25C to about 60C, increasing with the SoC you start charging at (lower percentage being cooler).

Preconditioning the battery in cold conditions is a trade-off: it takes a lot of energy, but it gives you stronger regenerative braking.

Don't take my word for it though, it's also on Page 78 of the current owner's manual, section "Regenerative Braking" under "Cold Weather Best Practices": https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf. This is the only explanation I could find for the suggestion of preheating the car (other than the obvious cabin/windshield benefits).
You'll also see the mentioned preheating for Supercharging just below, under "Warming the Battery Before Supercharging".

This is partly why they also recommend a ridiculous 30-45 minute precondition time. To make an actual difference, it needs to run for a while. The battery is big and has a lot of thermal mass, requiring a lot of energy to heat.

Lastly, this is a choice Tesla has left to owners. If it was something ultimately important and worth doing to the battery health, the car would just do it. An example of this is it doesn't let the pack get too far below freezing temperature at any time, even when parked.

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There are battery chemistries we have today (some very similar to what we already use) that last much longer, the caveat being that their operating and storage temperatures need to be very tightly controlled. We don't do this because it would be extraordinarily wasteful for EV battery packs, and/or lead to even smaller capacities (cooling/heating/insulation needs).

Just a couple of thoughts, the battery is liquid cooled/ warmed. In extreme cold might this be likely to freeze? Possibly why Tesla recommend to leave it plugged in. Not valid in summer I know.

Lithium-Ion batteries do not perform well below below 4 degrees, requiring significantly more of their capacity to achieve the same current draw at higher temperatures. While this does not harm the battery range is reduced.

Long term storage of Lithium-Ion should be at 50% of their capacity. I see no reason to ever go below this figure except for driving somewhere or if you want to recalibrate the BMS. The myth of discharging to 20% and recharging fully applied to Ni-Cad and Ni-Fe batteries and does not apply to Li-Ion.

The more you charge the battery without using it, the more the degradation but balancing the cells is really important and this only happens at higher stages of charge. Hence Tesla’s recommendation to charge to 80% for daily use.

Above 80% charging rate is reduced in order to balance the cells. Charging to 100% fully balances the cells and is not harmful to the battery but leaving the battery at 100% and allowing it to discharge internally is. If you charge to 100% use the car as soon as possible.

Finally I figure that Tesla worked out that drawing large amounts of current or charging at high current can only be done when the battery is warm, otherwise degradation may be increased. This is why I think they have reduced the regen in the latest software release. In a 30 mile journey I could not warm the battery enough for the regen to be restored.

My advice, always leave it plugged in and don’t worry about it. In cold weather below 4°C precondition before driving, 30 mins at least. This will guarantee your range and restore the regen. Happy driving

 

[Swordtail]

I've had my 2021 model 3 a couple of weeks now. So, purely from a range point of view, is it best to precondition the battery while plugged in for 30 minutes or so before going on a long trip? I'm guessing this means the car will use less energy heating the battery when driving as it's already heated up. Am I getting this right?

Cheers!

 

[Gasaraki]

I read your posts and I was also under the impression that Tesla figured it all out for me. Why then does preconditioning turn on battery heating (in winter)?

while I don’t use it on short trips I generally precondition for 10-15 min. I definitely like the feel of stronger regen. My car is garaged but going to work in the morning if I don’t preheat I find I end up using the friction brakes more even on a 50 min commute.

By preconditioning for 15 min using the mobile connector I’m consuming just shy of 2kW (this includes losses and cabin heat). And I like knowing the initial load of the cabin heater doesn’t come from the main pack. But I’m interested to read your thoughts.

Yes, people are complaining about that BECAUSE it doesn't make sense when I just want to reheat the cabin why do I have to waste energy to preheat the battery? The only time you need to preheat the battery in the winter are:

Heading somewhere to charge your battery. Cold battery charges very slowly.
You want high regen braking. The warmer the battery, the most regen braking you get.
You're driving so far that you need the extra blue section in the battery. (only in very cold batteries)

In all cases you will be spending more energy to try to heat that battery than you will get back from 1. better regen braking, 2. more efficiency from a warm battery. The only time it's worth it is if you are heading to a supercharger to charge, cause you might make up the extra time it would take to charge the extra energy you used.

 

[Gasaraki]

I've had my 2021 model 3 a couple of weeks now. So, purely from a range point of view, is it best to precondition the battery while plugged in for 30 minutes or so before going on a long trip? I'm guessing this means the car will use less energy heating the battery when driving as it's already heated up. Am I getting this right?

Cheers!

If you have it plugged in and you don't mind spending the extra energy, yes.
Preheating when unplugged is not worth it because you'll spend more battery power than you get back from increased regen and efficiency.

 

[MikeHolliday]

I live in Ohio, my car is in a garage with the Wall Connector plugged into the car. When the Outside temperature between 17 degrees and 42 degrees Fahrenheit, the garage averages about 10 degrees warmer than the outdoors.

I set the climate control on 71 degrees Fahrenheit and the Seat to medium 15 minutes prior to leaving and I get excellent regenerative braking. Unless the Temperature is super cold here like 5 degrees to 0 degrees Fahrenheit I think that preheating any longer is a waste.

 

[Swordtail]

The only time you need to preheat the battery in the winter are:

Heading somewhere to charge your battery. Cold battery charges very slowly.
You want high regen braking. The warmer the battery, the most regen braking you get.
You're driving so far that you need the extra blue section in the battery. (only in very cold batteries)

I'm interested in maximising range. There's a rare round trip I will need to make which will be border line do-able without a charging stop. The quoted range for the 2021 UK model 3 is 360 miles. On a recent shorter trip in 40 degree F temps I calculated it out to be not much more than 200 miles which I found disappointing. I know the range will be better in the summer (it rarely gets into the 80s in the UK) but I'm wondering how much higher that 200 range would have been had I preconditioned via the wall before the trip.

I agree no point preconditioning for any other reason than maximising range.

 

[SigNC]

preheating, plugged in, in the new models with the heatpump also has the added benefit of adding heat to the battery that can be extracted to heat the cabin. You are literally adding more energy to the pack in the form of heat.

 

[Darthbenji]

Where I live it’s likely to get below 0c for at least 5 months of the year. November to March. Maybe I’m being foolish but I’d like the Regen and the added cost of the energy over an untimely brake job. I’m happy to be corrected on that though.

 

[Gasman23]

One thing I have noticed in the cold, if I don’t preheat at all the battery can still have limited regen after an hour of driving. So the battery is stuck in a less efficient state.

Personally, I just preheat for 5mins as this is enough to bring the cabin temp up to a comfortable level and starts the process of recovering regen and battery efficiency.

Ultimately there’s a bit of hair splitting going on in this thread so do what you’re happy with and enjoy the car

 

[MikeHolliday]

I'm interested in maximising range. There's a rare round trip I will need to make which will be border line do-able without a charging stop. The quoted range for the 2021 UK model 3 is 360 miles. On a recent shorter trip in 40 degree F temps I calculated it out to be not much more than 200 miles which I found disappointing. I know the range will be better in the summer (it rarely gets into the 80s in the UK) but I'm wondering how much higher that 200 range would have been had I preconditioned via the wall before the trip.

I agree no point preconditioning for any other reason than maximizing range.

I have a Model Y with a Range of 316 miles. On November 29th, I left Atlanta, Ga. with 2 people in the car, about 50lbs. of luggage. I sat out on my 600 mile trip with the Heat set to 71 degrees Fahrenheit and the Seats set on Medium Heat. The Outside temperature was between 30 & 40 degrees Fahrenheit. I drove 65 - 75 miles per hour all day and hit 80 a few times. I probably averaged in the low 70's. I would describe this as a hilly drive. I preconditioned prior to leaving Atlanta. My last leg was Lexington, Kentucky to Worthington, Ohio is 199 miles. I left Lexington at a 90% SOC and arrived in Worthington, Ohio with a 19% SOC. Which means I used 71% to travel 199 miles.

 

[JCtx]

is it best to precondition the battery while plugged in for 30 minutes or so before going on a long trip?

As Gasman said, 5 minutes is enough. At least for me too, with the garage about 40F. My wife does it when she needs to leave early (not often), car hooked or not, and it's already toasty inside (72F), and battery has lots of regen, so that's enough.

I decided to hook the car up (NEMA 41-50) every 2 to 3 days, top it off to 80% only, and not let it below 60%. Read that the ideal battery range is 60 to 80, so that's what I'm doing when not traveling. And by not connecting it every single day, the battery is going to read lower values the other day or two, hopefully not decreasing the screen range too much. We have an upcoming long trip next week, where the first leg is 135, so will only charge it to 90%, since I don't need 100%. Will travel that stretch fast (80 speed limit), and we'll need the heat, so curious how much range it eats there. The second stop is 250 miles away, so too risky trying to make it there in one shot; I'd have to slow down dramatically, so rather do it the sure way. Will have to make 4 stops total, it seems, plus a 5th in Austin, to top off the car, to use it there. Looking forward to the adventure. Ha ha.

 

[SigNC]

I have a Model Y with a Range of 316 miles. On November 29th, I left Atlanta, Ga. with 2 people in the car, about 50lbs. of luggage. I sat out on my 600 mile trip with the Heat set to 71 degrees Fahrenheit and the Seats set on Medium Heat. The Outside temperature was between 30 & 40 degrees Fahrenheit. I drove 65 - 75 miles per hour all day and hit 80 a few times. I probably averaged in the low 70's. I would describe this as a hilly drive. I preconditioned prior to leaving Atlanta. My last leg was Lexington, Kentucky to Worthington, Ohio is 199 miles. I left Lexington at a 90% SOC and arrived in Worthington, Ohio with a 19% SOC. Which means I used 71% to travel 199 miles.

I'd call that excellent. That's 280 miles range at interstate speeds in cool weather. Thank your heat pump and it's ability to scavenge heat out of the battery/motors.

 

[hgmichna]

Read that the ideal battery range is 60 to 80, so that's what I'm doing when not traveling.

Ideal for what? Where did you read that?

For absolutely minimal degradation 40% to 60% is ideal, but up to 80% the difference is small. Even so, you could say 20% to 80% is ideal.

 

[Justin L]

Where I live it’s likely to get below 0c for at least 5 months of the year. November to March. Maybe I’m being foolish but I’d like the Regen and the added cost of the energy over an untimely brake job. I’m happy to be corrected on that though.

I wouldn't worry about a brake job; even with reduced regen in the winter for part of the drive, you're still going to have years and years before you need a new set of pads. The thing that will kill your pads faster than reduced regen is if you are relying on the traction control and e-diff to modulate which side is getting power.

 

[MikeHolliday]

I don't worry about Brake work either, but I do like one peddle driving, a warm car and increased range...

 

[JCtx]

Ideal for what? Where did you read that?

For least battery degradation over the years. And I don't know what to believe anymore. Ha ha. Have read tons of conflicting info, so decided to take the middle ground between what Tesla recommends (leaving car hooked up all the time at 90%), and to what supposedly is the best approach, which apparently is to let it drop to about 20/30, and charge back to 80%. So I figured I can't go wrong by doing 60 to 80%. Ha ha.

 

[hgmichna]

Tesla has never recommended to leave the car hooked up at 90%. They only indicate that 90% is the maximum for charging, unless you occasionally go on a long trip and need more. That does not mean that 90% is best for the battery.

Tesla has absolutely never recommended to let the state of charge drop to 20% or 30% before recharging, and it does not make sense anyway.

People say weird things. If you want to get to the truth, a good source is Battery University, better than forum chit-chat. Anyway, with 20% to 80% most of the time you don't go very wrong.

A caveat is that the new LFP batteries in the Model 3 SR+ Made in China are different. They can be charged higher and should be charged to 100% about once a week.

 

[Ron7136]

No, Tesla knows how whiny customers are and that's the math they use.

In my experience it never "pays" to Preheat cabin or battery. Especially on a very short commute. But even on long ones it doesn't "pay" (it's a net loss on energy for more comfort).[/QUO
This is NOT a YES/NO question. For short drives it is not worth preheating but if you need MAX range then absolutely preheat the cabin. For shorter drives it would depend on the value you place on getting into a warm car.