Road Trip Starting Charge %

[hinkbot]

Perhaps this is a fictional use case but wanted to be prepared just in case.

In the next month or so I will have a level 2 charger at home and a new Supercharger site 5 miles EAST. My concern would be an urgent need to drive 300 miles (family health) WEST. I plan on keeping a healthy SOC but things come up.

In the event that happens with a lower SOC (less than 50%), would navigation route me East first? Would it be better to just drive to the local charger first before entering navigation? Or would it be better to see what it’s recommending and make a decision based off that (evaluate how much SOC is left at first fill up).

Not an extremely likely situation but was curious what folks experience has been.

 

[NWMY]

Don't over think things. You will not get 300 miles on one charge. Leave your place with enough to get to a half way supercharger and leave that one with enough to get to a supercharger near your destination. Same coming back.

 

[Sophias_dad]

You would definitely not be better going the the SC first. Jamming that last few percent into the battery will take FOREVER, whether its on the L2 or SC.

You >might< get 300 miles on the Y on the highway, with a tailwind. You definitely shouldn't count on it, nor should you plan(ever) to arrive anywhere, even a SC, with less than a few percent remaining. What if the charging equipment is broken?

There are TONS of SC's on the east coast, use one on your way, usually starting at 10-30% and ending at 80% or something like that when the charge rate drops considerably.

 

[Rocky_H]

We have no idea and can't answer, because you never said how far to the West the first Supercharger is. It's probably closer than 300 miles.

As people are trying to point out, this gas car mindset of: fill 'er up, drive-to-empty, fill 'er up again, etc. is a totally awful way to use an electric car and makes for a really bad experience. Shorter hops and filling only up to about 70-80% is much faster charging and quicker total travel time.

 

[LoudMusic]

In my experience if I needed more charge to reach a destination and the only Supercharger available was the wrong direction, it would very much route the opposite direction to get charged up.

 

[Tronguy]

Been driving a Model 3 LR RWD around the landscape on the East Coast since 2018. When new, range was nominally 320 miles or so. (It's a bit less now, that's expected.) The garage has a L2 Tesla Wall Connector.
Usual trick from central NJ to Boston is to charge to 100%, using the, "100% at the time we're leaving" function built into the car, load the address into NAV, and blow out of here.
During the warm months, NAV will have one stopping in Central CT somewhere or, if it's feeling frisky, Central Massachusetts somewhere. Point: One is (a) trying to minimize charging time and (b) arrive at one's destination with enough charge so one doesn't get stranded.
On (a), the car charges at max rate when the battery is below 50%, preferably around 20%-30% to get that V3 250 kW SC experience of 1000 Miles of Charge per Hour. On (b), the NAV will try to get one at one's destination with 10%-15%.
So, as a result of the two things above, NAV will tell one to stop at some SC for, say, 15 minutes or something, and then urge one to go on. But! One would like, say, 25%-40% charge when one gets to the destination.
Solution: Instead of hanging out at the SC for 10 minutes, take a longer break and hang out for 20. Or 30. By no means go over 80% of charge at the SC: Charge rates drop dramatically if one does that. But, having said that, staying a bit longer at the SC will get one to one's destination with enough charge to run around for a while.
Now, cold months in a 2018 M3 can get interesting: energy use goes from 250 W-hr/mile to 350+ W-hr/mile, so one's 300+ range drops to 215+ miles; so, there might be two stops, rather than one, and the second one is when one hangs out for a bit longer. But Model Y's come with a heat exchanger so their mileage drop is quite a bit less. So you may or may not need that second stop.
And there you go.

 

[MYMY21]

Don't over think things. You will not get 300 miles on one charge. Leave your place with enough to get to a half way supercharger and leave that one with enough to get to a supercharger near your destination. Same coming back.

And even consider leaving with lower state of charge so that you are in the 10-20% range when you hit your supercharger. You might be leaving with 70% charge to start. No way to know for sure without the specifics.

 

[LoudMusic]

And even consider leaving with lower state of charge so that you are in the 10-20% range when you hit your supercharger. You might be leaving with 70% charge to start. No way to know for sure without the specifics.

I think that's only true when departing from a Supercharger. If you're leaving from somewhere that the car can charge "for free" indefinitely you might as well charge it up as much as possible. Even though the only charge time you're avoiding is the fastest charging speed, you're still avoiding that much time at the Supercharger. And, it's definitely going to be cheaper electricity at home than at a Supercharger! Ha!

 

[MYMY21]

I think that's only true when departing from a Supercharger. If you're leaving from somewhere that the car can charge "for free" indefinitely you might as well charge it up as much as possible. Even though the only charge time you're avoiding is the fastest charging speed, you're still avoiding that much time at the Supercharger. And, it's definitely going to be cheaper electricity at home than at a Supercharger! Ha!

Depends upon your priority. If fast charging is most important, only charge enough to get to the next stop. Even 10-20% on the battery makes a difference. I know it is counter intuitive, but a higher state of charge when arriving at the supercharger can mean a slower charge and more time there to get to the next stop.

 

[LoudMusic]

Depends upon your priority. If fast charging is most important, only charge enough to get to the next stop. Even 10-20% on the battery makes a difference. I know it is counter intuitive, but a higher state of charge when arriving at the supercharger can mean a slower charge and more time there to get to the next stop.

Is the rate of charge at a given state of charge different based on what the state of charge was at the beginning of the charge session?

For example, if I leave home at 95% and arrive at the first Supercharger at 50%, will the rate of charge at that 50% be lower than if I leave the house at 55% and arrive at the Supercharger at 10% when it reaches 50%?

If it's the same, then I'm behind because I had to wait for it to get from 10% to 50%. It's quick there but still does take time.

The logic for leaving Superchargers with only enough to arrive at the next one with 10% holds true because there's no reason to wait for that higher SoC slow charge rate versus the arrival lower SoC charge rate. But departing from home or hotel or where ever the car has sat for several hours on an L2 charger - might as well just set it to charge to 100% before you depart so the first charging session is quicker and cheaper.

 

[MYMY21]

Is the rate of charge at a given state of charge different based on what the state of charge was at the beginning of the charge session?

For example, if I leave home at 95% and arrive at the first Supercharger at 50%, will the rate of charge at that 50% be lower than if I leave the house at 55% and arrive at the Supercharger at 10% when it reaches 50%?

If it's the same, then I'm behind because I had to wait for it to get from 10% to 50%. It's quick there but still does take time.

The logic for leaving Superchargers with only enough to arrive at the next one with 10% holds true because there's no reason to wait for that higher SoC slow charge rate versus the arrival lower SoC charge rate. But departing from home or hotel or where ever the car has sat for several hours on an L2 charger - might as well just set it to charge to 100% before you depart so the first charging session is quicker and cheaper.

Yes to the first question. I’m not certain about the second question. It might be the same. But the point is that unless your next supercharger is very far away, you’re not going to charge back up to 95% again. The principle behind fast supercharging is to arrive as low as possible and charge just enough to get to the next stop.

 

[Johnny Vector]

Yes to the first question. I’m not certain about the second question. It might be the same. But the point is that unless your next supercharger is very far away, you’re not going to charge back up to 95% again. The principle behind fast supercharging is to arrive as low as possible and charge just enough to get to the next stop.

Er, I don't think so. I see only one question there, and the short answer is no. The charge rate (assuming it's limited by the car) is a function of state of charge and battery temperature. I think that's what you're saying here, and one of us is misunderstanding LoudMusic's question. Anyway, the SOC you start charging at is (almost) irrelevant to the charge rate at any give SOC later in the charge session.

Well, except if you get into real details, if you started from a lower SOC, the battery will be warmer by the time you get to (say) 50%, so you'll charge (slightly) faster. But if the car routed you to the Supercharger, it will have preheated the battery as you got close, so that effect doesn't apply in real life.

The key is to get to the SC with as low a SOC as you're comfortable with. I generally aim for 10-20%, as determined by the navigation system while I'm charging at the previous SC. I always do better than it thinks I will, so I arrive with maybe 5 more percentage points of charge than it thought I would.

When starting out from home, I no longer bother to charge to more than 90%. It makes so little difference to the total trip time, and I prefer having full regen, which you lose at higher charge levels. At 90% I don't have to touch the evil, evil friction brakes. We hates them!

 

[LoudMusic]

That's what I was getting at. Charge speed at a given SoC is the same regardless of the starting SoC.

I prefer to leave the house with as high of charge as possible. Mentally it feels good. And allows me to drive ... quickly.

However, I do leave Superchargers with enough SoC to arrive at the next Supercharger with between 10 and 15 % SoC. No sense sitting around at 45kw when we can arrive at the next one and get 145 up to 250 kw. Though I have found lately that the car does not update arrival percentage in real time while charging. And while charging it's not particularly accurate either. When I unplug from the charger my arrival value often changes from 10ish to like 20+. Then during the drive it will fluctuate a little, and I push it a little and end up arriving at 12 to 15. I'm not brave enough to unplug and leave before it shows 10% arrival though .