Should I charge to 100% (night before trip) if my first supercharger stop is only 80 miles away?

[Canuck]

Really? You spend all this discussion time on how to save a few minutes.

It's a Tesla forum and some of us find these discussions interesting. If you do not, then there's no reason to read these threads. I drive to my cabin almost every weekend and the supercharger is 100 miles away. I find it interesting to figure out of the best way to save time, least degradation to the battery, etc.

You ever choose Mickey D's over a nicer restaurant so you can save a few minutes?

No. I'd rather go hungry than eat that garbage.

You never go to town, because you might have to wait at a red light?

Of course, but if I could figure out how to make the light change in my favour to save time (legally), I'd be interested in reading about how to do it.

Waiting a few minutes is not the end of the world.

We're not saving the world here. Reducing an argument to absurdity proves nothing.

 

[animorph]

The OP will be charging to the same SOC at the first SC, regardless of the initial charge at home. That would be the charge required to make it to the next SC, plus a safety margin. No point charging more than that, which would just waste time.

If the car is charged to 100% at home it will arrive at the first SC with 10% more SOC and require less time to reach the desired SOC leaving the first SC. If the car is charged to 90% at home, that missing 10% will have to be added at the first SC, taking that much extra time.

100% home charge - 40% used to reach first SC + 30% charge added at first SC = 90% charge leaving first SC.
90% home charge - 40% used to reach first SC + 40% charge added at first SC = 90% charge leaving first SC.

After the first SC the SOC is the same for either case, so there will not be any other difference between the two cases.

You can trade of the time saved at the first SC versus the "risk" and effort required to charge 100% at home.

 

[bob_p]

While we talk about the range of the car being how far the car can go with a 100% charge, the practical range is much less than that.

You typically want to keep the charge at least 10% (to provide some emergency buffer for unexpected challenges requiring more energy to get to the next charger).

And, you want to keep charging at an SC below 80%, if possible (above 80%, charging speed slows down considerably).

When planning highway trips, we use a crude "30-30" rule. Using the rated range for the battery pack and the distance to the next charging location, we take that distance, add 30%, and then add 30 miles. That will be the minimum charge we want to have in the car before we leave home or leave a supercharger.

Leaving after an overnight charge with 100% can help for the first charger stop, but after that, it won't have any significant impact on the overall driving/charging times. And regularly charging above 90% does risk accelerating battery degradation.

If you can leave a charger with more than the 30-30 amount (either after overnight charging or charging while at a restaurant), then you might be able to skip a supercharger or at shorten (by a few minutes) the time at the next supercharger. Though unless we're in a big hurry, we're more likely to leave with a 90% charge - and not risk accelerating battery energy loss.

 

[Ibrido]

I understand that you actually supercharge faster the lower your SOC when you arrive at the charger. The first leg of my trip will only be 80 miles, so I'm wondering if it really matters if I charge to 100% the night before or if 90% is better or won't really make a difference. I have a MS 70D.

Slow charging is better for battery's long life. Supercharges charge it quickly so IMO it would be good to skip Supercharges wherever possible ! (In your case, the 1st charging instance)

 

[ItsNotAboutTheMoney]

Really? You spend all this discussion time on how to save a few minutes. You ever choose Mickey D's over a nicer restaurant so you can save a few minutes? You never go to town, because you might have to wait at a red light? C'mon. Waiting a few minutes is not the end of the world. Even buying gas at Costco took time, and you had to pay for it! Oh, well.

Imagine Superchargers had a pay-per-use element. Would it change your advice? To me this is actually a non-trivial discussion and the discussion exists only because Superchargers are free at point of use.

If the OP asked Elon Musk or JB Straubel they would ask, with an exasperated expression, "Why would you want to waste unnecessary time at the Supercharger?"

There is also a risk of additional time spent at a busy Supercharger by virtue of having to wait, or being the 2nd of a pair. And the more unnecessary minutes of charging at Superchargers, the more likely such situations are to happen. Public charging of BEVs generally has a capacity challenge, and extra unnecessary minutes occupied either require additional infrastructure that add to the overall cost of charging, or add to waiting times.

To me it's simple: anyone driving beyond range should try to leave home with 100% charge.

And on the restaurant front one thing I learned on a long drive: better to get fast food and eat on the go than stop and sit down at a low-grade chain and waste time.

 

[Saghost]

Imagine Superchargers had a pay-per-use element. Would it change your advice? To me this is actually a non-trivial discussion and the discussion exists only because Superchargers are free at point of use.

If the OP asked Elon Musk or JB Straubel they would ask, with an exasperated expression, "Why would you want to waste unnecessary time at the Supercharger?"

There is also a risk of additional time spent at a busy Supercharger by virtue of having to wait, or being the 2nd of a pair. And the more unnecessary minutes of charging at Superchargers, the more likely such situations are to happen. Public charging of BEVs generally has a capacity challenge, and extra unnecessary minutes occupied either require additional infrastructure that add to the overall cost of charging, or add to waiting times.

To me it's simple: anyone driving beyond range should try to leave home with 100% charge.

And on the restaurant front one thing I learned on a long drive: better to get fast food and eat on the go than stop and sit down at a low-grade chain and waste time.

Eating on the go = distracted driving - possibly mitigated somewhat by Autopilot.

Current thinking is that a break of ten or fifteen minutes every couple hours on long tasks is good for both competence and exhaustion.

On a Tesla roadtrip, you probably needed to waste that time somewhere - better in a restaurant than sitting in the car drumming your fingers.

 

[kort677]

Its always faster to range charge at night.

why?

 

[Saghost]

why?

Because that's time you aren't waiting for the car.

The charge itself will take the same amount of time it all always does on that source - but while you're in bed it doesn't matter whether it takes 5 minutes or 6 hours, as long as it is ready to go when you finish breakfast.

This is also why you should charge for the whole lunch and dinner stops rather than just enough to reach the next stop - it means less time waiting for the car at breaks in between.

 

[dgpcolorado]

for 80 miles to SpC I will charge to 90% at home so that regen braking still works for the first few miles. A 100% SoC prevents the regen from working.

I do this too. I've tried 93% to 95% but the drastically reduced regen presents a safety issue because I have to descend a steep — as much as a 14% grade — thousand foot hill with hairpin turns whenever I leave home and I don't like to friction brake my way down.

For flatlanders, 100% will likely work ok for starting out on a road trip so long as they remember that there will be no regen when they back off the go pedal for the first few miles; it can be a bit disconcerting when one is used to the car slowing in that situation.

 

[WannabeOwner]

so long as they remember that there will be no regen when they back off the go pedal for the first few miles

I always forget - 100% charge is not common, always at the start of a trip, I probably have other things on my mind at the moment when we set off. Its definitely disconcerting ... but doesn't last for long.

Whilst I rather like one-pedal-deriving I would much prefer that regen was on Brake pedal, and Brake pedal always worked the same (i.e. Regen if available, but pads if not). It takes a lot of brake pedal pressure, compared to normal, to stop 2.5 tons when there is no regen available ... and I would be able to drive smoother if foot off Fast pedal just gave me neutral; right now coming off Cruise Control and trying to get onto Fast pedal with same amount of forward motion is a dance / guess, and rarely 100% smooth for my passenger.

 

[bxr140]

To me it's simple: anyone driving beyond range should try to leave home with 100% charge.

Agree. Of course, there are plenty of cases where one won't slide into range for a trip (regen preference, don't care about trip time, etc), but at the risk of coming across a little abrasive, I'll take your comment one step further: If long term 'harm' makes one think twice about moving their charge slider into range zone, one has allowed incomplete information and FUD to miseducate.

Tesla is okay with it.
The chemistry is okay with it.
Extreme empirical evidence is okay with it (Tesloop).

 

[dgpcolorado]

I always forget - 100% charge is not common, always at the start of a trip, I probably have other things on my mind at the moment when we set off. Its definitely disconcerting ... but doesn't last for long.

Yes, it is a surprise at first but usually easily recovered from. (Unless you hit the car in front of you!)

Whilst I rather like one-pedal-deriving I would much prefer that regen was on Brake pedal, and Brake pedal always worked the same (i.e. Regen if available, but pads if not). It takes a lot of brake pedal pressure, compared to normal, to stop 2.5 tons when there is no regen available ... and I would be able to drive smoother if foot off Fast pedal just gave me neutral; right now coming off Cruise Control and trying to get onto Fast pedal with same amount of forward motion is a dance / guess, and rarely 100% smooth for my passenger.

I'll disagree. I greatly prefer single pedal driving and have gotten quite good at feathering the Go pedal when switching off cruise (or switching back to D from N, something I can do here safely, given the lack of traffic).

One thing I particularly like about single pedal driving is that when I back off the Go pedal in a rapid stop — because of a deer on the road, say — the car is already slowing before I even get to the brake pedal. This similar to a conventional ICE transmission, which uses engine compression to slow when one backs off the "gas". Having neutral be the off setting on the Go pedal seems less safe to me. The Model S coasts really well and slows hardly at all in neutral unless one is going uphill. And if just I want to coast on the Go pedal it is trivial to pick the zero energy position by feathering the pedal, something I often do. The ability to fine tune speed with strong regen on the Go pedal is one of the things I most like about driving the Model S, especially when driving steep hills and hairpin turns.

 

[WannabeOwner]

I don't knock the S into Neutral - whereas I used to knock the Stick-Shift ICE into Neutral often (for hypermiling)

Is there any reason not to shift into Neutral in an S in order to coast? Any harm going to come to anything, or other things to be aware of?

I would certainly find Neutral easier than trying to feather the throttle to get exactly 0 kW (which requires eyes-off-road to check the instrument cluster)

 

[GasKilla]

Lots of good input here, I think I'm going to charge to 100% the night before the trip. But I am curious how "bad" it really is to charge to 100% and let the battery sit for a few hours before I leave? I am pretty close to the freeway so not having regen at the start of my trip shouldn't be a problem, but I do appreciate the reminder about loss of regen.

 

[HankLloydRight]

I would be concerned with the "few hours" part. If I charge to 100% I really try to start driving within the hour. I'm no battery expert, but I think three or four hours sitting at 100% gets into the danger zone of internal heat building up inside the cells.

 

[bxr140]

I am curious how "bad" it really is to charge to 100% and let the battery sit for a few hours before I leave?

Nobody really knows, but a single event like that is going to have an infinitesimal impact on "bad". There's no argument that theory says it's worse to leave a battery at high SOC, so the more you do it the more likely you are to incrementally increase the sum of "bad". Given the empirical evidence though, it's really not going to matter much either way. It's something that you should manage only to the edge of convenience. Its not something that warrants paranoia.

As previously noted in the thread, the generally accepted compromise in your kind of situation is to charge your car to 90% overnight then use your app to (re)set the charge limit to 100% in the morning, an hour or so before you leave. It will top off as you're brushing your teeth and making sure the kids put on clean chonies.

If your morning routine is efficient and your SOC than 100% before you're ready to head out, it's fine. If it sits at 100% for a bit because the toilet overflowed, it's fine.

Another option is to adjust your charge amperage when you put it on charge the night before to charge slower/longer than usual, and try to time it so it finishes when you plan to leave in the morning. IMHO that's too much fussing compared to the morning top off, but different strokes...

 

[bxr140]

Is there any reason not to shift into Neutral in an S in order to coast? Any harm going to come to anything, or other things to be aware of?

Other than a general concern of distraction with hypermilers being more focused on fuel economy than driving? No.

I would certainly find Neutral easier than trying to feather the throttle to get exactly 0 kW (which requires eyes-off-road to check the instrument cluster)

Its not hard at all to keep it within +/-5kw, which will net you the same apparent efficiency as neutral coasting, plus it will allow the driver to more closely follow the flow of traffic.

 

[WannabeOwner]

Thanks. its not generally the flow of the traffic that I would hypermile for. My best example is the school run; a rural route across country, where invariably I don't see another vehicle. When I first started hypermiling that route (more than a decade ago) the ICE I had probably didn't have "lift off and adjust injectors to use zero fuel" (I'm sure there is a name for that) which more modern engines now have. I started learning landmarks representing a particular speed and from which I could coast (in Neutral [stick-shift ICE]) so that I would arrive at the next bend at safe speed to take the corner, or lose speed for a junction, having bled enough speed without resorting to using the brakes. That alone improved reduced my fuel usage by 30%, which was a huge surprise to me at the time (given that over a lifetime of driving that would represent more than 10 years of free driving), so that's the sort of scenario where I would prefer to select Neutral instead of trying to feather the accelerator as close to 0 kW as possible. I will give it a try; my expectation is that I will be able to select Neutral eyes-on-road, which I can't do when feathering to 0 kW.

That said, unlike Gas where using the brakes wastes [some of] the fuel that was used to accelerate, Regen is going to get me back 70%-ish? of the energy, so unlike Gas & Brakes the Regen in the MS is far more efficient than regular gas driving.

Perhaps I should try the school run:

A) Driving like a bat-out-of-hell !! heavy on the brakes
B) Trying to completely avoid use of brakes and just use Regen
C) Same again, but attempt to maximise hypermiling using neutral to coast whenever possible.

If I find that B & C are within a whisker of wH/M I can abandon the whole idea of hypermiling and just try to Regen instead of Brake

I could do with Waze giving me Yellow / Red lights / warnings indicating [Yellow] the latest point at which 100% Regen will bleed off all excess speed for, say, a junction causing me to arrive at, say, 20 MPH and [Red] same thing but arriving at, say, 40 MPH. If no one behind me and/or some traffic at the junction ahead I can go to full regen when the Yellow appears; if someone behind me I can wait until the Red to start the full Regen (and waste some energy for the final braking but without annoying the guy following).

I'd like that sort of logic to be available when fully autonomous vehicles become commonplace, nothing to stop Robots from diligently saving fuel ...

 

[TexasEV]

Slow charging is better for battery's long life. Supercharges charge it quickly so IMO it would be good to skip Supercharges wherever possible ! (In your case, the 1st charging instance)

No, supercharging a Tesla does not have material impact on the battery life. We do not have to skip superchargers whenever possible! Stop scaring people who (unlike you) are actually driving Teslas now.

 

[thecloud]

Adding to what @Three60guy said, I would take the navigation system's suggestion as a bare minimum and charge more than it recommends, to give yourself a margin of safety. Some recommend having enough charge for 150% of the miles you plan to need.

Last weekend, starting out on a 200-mile trip down Hwy 101 at just over 90% charge, the car's navigation system initially estimated that I would arrive at my destination with 20% charge remaining. No problem, right? As the trip progressed, driving on TACC between 65 and 70 mph, I watched that estimate gradually go down from 20% to 6%. Then the car started popping up warnings that I should go less than 65 miles an hour if I wanted to make it (I was doing 65 at this point and was already the slowest car on the road.) Then that number went down to 60 miles an hour. It seemed as if the car's estimate was not taking elevation changes and wind into account, or the added weight of passengers and luggage, and probably was based on a 55 mph rated range.

Fortunately, there was a charger in range that I had planned to skip, and so I just re-routed to stop there. Lesson learned: I would have made it all the way to my destination without stopping had I given myself the extra margin by charging to 100% before leaving the house. I also would have made it if I slowed down to 55 mph, but that isn't always desirable or safe on a highway.