Best Highway Speeds

[HighZ]

I am a new owner (almost! order placed) of an M3 AWD LR - 18" wheels with dark silver ext and black seats.

I live in northern Illinois and commute 120 miles daily almost all via freeway. I currently spend almost $7000 in gas & oil per year driving 30,000 miles, so I was excited to move to electric to reduce that cost.

However, I am wondering how efficient my drive will be and what people have found are efficient speeds on the highway. The speed limit for my route is 70 mph and I typically drive 80-85 mph the whole way.

I plan to charge to 80% at home and have a charger also installed at work (also to help with warming up the car in the dead of winter), so I don't think I would ever have an issue with charge. But given that I have heard the battery should be charged to 80% and not go lower than 20%, that leaves only 60% of use. Is that correct? So a 310-mile range becomes 180 miles usable. Enough for a round-trip, but then what penalty can I expect doing only highway speeds, and then when it is below zero at the same time?

I tried searching for this info, but didn't find much other than stop and go driving is better than full-out speed.

What speeds would you aim for most range and given that there is enough charge and is there more than average wear and tear doing 80+ day after day?

 

[lolder]

Driving 80+ in cold weather against headwinds can reduce your rated range 50%. You'll need the work charger. Running the battery 10-90% is not too bad but you want more reserve in winter than 10%. The slower you go, the more range down to about 20 mph but high cabin heating or AC demand eat into it. M3 heating is all electric resistive heating and sometimes the AC has to be on also even in cold weather to keep the windshield defogged.

 

[Uncle Paul]

HighZ.

You are in a perfect circumstance. Leave your house with an 80% charge. Drive as fast as you like, going to work, then charge there back to 80% for your trip home (also driving as fast as you wish)

Tesla will charge quickly at both ends, and give you absolute freedom for driving speeds...both ways.

Enjoy your new Tesla.

 

[SleeperService]

What @Uncle Paul says above. I've got an 80 mile (round trip) freeway commute every day. I drive ~82 mph (well, that's where the AP is set, traffic is sometimes slower...). I'm in northern Indiana, so similar climate to you. It would be NICE to have a charger at work, if for no other reason than to keep the battery warm so that I have regen braking on my way home when it is cold out, but even when it is COLD out I generally only used ~45% of my SOC (from 80% when leaving home in the morning down to 35% when I arrive back in the evening), so I wouldn't anticipate you having any trouble even if you DIDN'T have the charger available at work. Also, charging to 85-90% every day isn't really going to be an issue if you needed to do so.

 

[ewoodrick]

Normal cold weather reduces range by about 30%
Driving 85 is going to drop your range by about 30%

Slow down to 65-70 and you'll hit the published range in warm weather and only take a few minutes longer.

 

[HighZ]

Wow! Thank you for all the concise responses.

I will look forward to getting the car to do these range comparisons, but it helps to have this information in my head. I have seen there are some apps that will do a good job tracking that.

It would be great to have a graph of range vs. speed at various temps. I am anticipating on those days the polar vortex hits (-20F), I will be working from home.

 

[brianman]

But given that I have heard the battery should be charged to 80% and not go lower than 20%, that leaves only 60% of use. Is that correct?

No, it's incorrect.

I'm going to guess you have used a cell phone or a laptop. If someone told you that you can never charge it to 100% and never let it drain to 0% or "bad stuff happens" you probably would think they are nuts. And you'd be right.

Now, if the same person said "If you want the battery on your phone/laptop to last for 50 years, then you might want to optimize as follows...." that person might be technically right but I would say he/she is nuts to expect or want to use the same phone/laptop for 50 years.

Now, getting back to the car. If you're buying a Model 3 to use as your daily driver, I recommend the following:
1. For trips you're fine charging to 100%, but it's a bad idea to leave it at 100% SOC (state of charge) for hours or days. It tends to stress the battery. That doesn't mean it'll explode in 15 hours if you charge to 100% and don't drive it until the next day. It means you might if you measure it obsessively discover that the battery range might be slightly less than someone who does obsess about it.
2. For daily use, Tesla implicitly recommends charging to the 90% (last tick before 100%) regularly. The cars are delivered with that default because Tesla is comfortable doing so.
3. It's ok to run down to low % (I've been to "0%" and near 0% on multiple Tesla vehicles, multiple times with no subsequent drama related to battery degradation) but -- like 1. -- don't let that state persist because, again, it stresses the battery.
4. After a month of having the car, if you want to obsess about the optimal charging value to use daily you'll have plenty of time to find like-minded folks here (TMC) or elsewhere to discuss it with in depth. Speaking for myself, I've got better things to do.

 

[Leafdriver333]

I would charge to 90%.
You will make it to your work no matter how fast you drive in your LR.
I would charge again at work to 90% and drive home at normal speed, 82mph or whatever.
Then you will get the feel of the range and consumption rate.

 

[P-Lo801]

I found this to be quite informative:

Best practices for Model 3 battery charging

 

[HighZ]

Thanks for that analogy. I fly drones and it is a very similar concept. Never store the batteries at full charge because they can heat up and expand. But when I am using the batteries, I fully charge.

[QUOTE="brianman, post: 3617030, member: 8762"

I'm going to guess you have used a cell phone or a laptop. If someone told you that you can never charge it to 100% and never let it drain to 0% or "bad stuff happens" you probably would think they are nuts. And you'd be right.[/QUOTE]