BATTERY & CHARGING (Quick Reference)

[MSR]

Several previous posters have said that "it's faster not to charge to 100%." That is NOT always true.

While it is true that it's always faster to begin charging at a lower State of Charge (SoC), if starting out from home or a destination charger with a higher SoC (not necessarily 100%) allows you to skip one or more SuperCharger (SC) stops entirely, that will be faster.

After leaving for the day, only charge long enough to to reach the next SC (plus whatever margin of safety you've comfortable with).

 

[gregincal]

It's not necessary to charge to 100% for a road trip (first page of your document). Actually, it could be a detriment to fastest overall time.

The Tesla Model 3 Long Range will charge at full speed from about 10% to 45%, so I certainly want to arrive at the first Supercharger with a remaining charge of 10% to something less than 45%. If that first one is only 100 miles away, then a full charge on departure will have me arriving with 310 - 100 miles, or about 70%. The Supercharger will be REALLY slow then.

Charge enough to start your trip exactly how you should end the trip... charge enough to get to the next Supercharger plus whatever extra you might be comfortable with.

But wouldn't you in that case just skip that supercharger? Certainly my road trip strategy is to always charge to 100% overnight and then drive to the furthest supercharger I can reach. After that I charge to smaller percentages.

Basically don't think about the amount of charge you are gaining from a supercharger, but the battery percentage you need to have when leaving that supercharger in order to get to the next stop. Arriving at a higher state of charge will always allow you to get to the target state of charge faster than arriving with a lower state of charge. If you arrive with a state of charge higher than the target, you don't even need to stop.

So yes, in general you always want to charge to 100% before a road trip.

 

[animorph]

But, that’s the point... it does cost extra time to charge to 100%. You can stop the charge with the app (I think) at your house, or set the required charge state from the app. if you’re at a hotel, you aren’t going to leave your non-charging EV at a public charge station, right? Go move it!

Unless you count the time to pull up an app on your phone as too much effort, it is worth your travel time to not overcharge.... even if you’re stuffing your pie-hole at a restaurant.

I think you’re confusing convenient and easy with best practice.

I'm not following this at all. Are you saying I can travel faster if I use the app to stop charging at say 80%, or maybe just enough to make the next SC, even though I may take another 20 minutes to finish dinner at the current SC? It takes zero extra time to continue charging, since I'm not going to leave until 20 minutes later, additional charge or not.

If I'm stopped at the SC, I'm going to be charging, right up to 100% if I'm doing something else that is delaying me. At best I might be able to skip an SC with the extra charge. At worst, I will be charging for less time at the next SC because I'll arrive with, say, 30% SOC instead of 10% but charging to the same departure SOC that makes it to the next SC. Same thing goes for charging at home at the start of a trip, 100% SOC (just before we take off). Again, it costs no travel time and saves a few minutes at the next SC stop.

At a hotel with a Supercharger I'll charge to 90% at night, move the car to a normal parking spot over night, then charge it to 100% in the morning while we're eating breakfast if it's not too much trouble.

Here's the major thread on this topic:

How to save a lot of time on long trips

 

[animorph]

Setting the charge limit to 100% during a trip might also save you some idle fees if you are delayed...

 

[TonyWilliams]

There is one other factor I do not see mentioned in the discussion of charging times. The assumption seems to be that one can get off the intended route, hook up, charge as desired, then return to the route, all with no loss of travel time. But in fact, that is rarely the case, at least in my experience. Some superchargers are some distance off your route, in which case the time to get to and from the supercharger site is an "overhead" cost that needs to be considered.

Au contraire, I did include time for both issues:

1) 5-10 minutes was included for “dwell time”
2) time was added since 70mph on the freeway is never 70mph average speed

 

[TonyWilliams]

At a hotel with a Supercharger I'll charge to 90% at night, move the car to a normal parking spot over night, then charge it to 100% in the morning while we're eating breakfast if it's not too much trouble.

Here's the major thread on this topic:

How to save a lot of time on long trips

Whether you do that, or not, doesn’t make it the fastest overall travel time.

The reason is self apparent in the charge speed graph.

Again, convenience over maximizing travel time.

 

[TonyWilliams]

x

Adding 150 miles is only 20 minutes of actual charging (0.33 hours), when charging from 50 rated miles to 200 rated miles

Add ten minutes dwell time for each stop, so 0.5 hours “blocked” per 150 miles added.

Driving 70mph might only have an average speed of about 60-65mph. But, consumption must be calculated at 70mph, if that’s what you’re driving on that perfect day with no wind on dry, level roads. I recommend using 60mph for calculating average travel time at 70mph.

Thankfully, rated range equals actual miles in the above scenario.

23-25 hours travel (1500 miles @ 60-65mph average)
4.5 hours (9 charge events at 0.5 hours)

 

[gregincal]

Whether you do that, or not, doesn’t make it the fastest overall travel time.

The reason is self apparent in the charge speed graph.

Again, convenience over maximizing travel time.

You really are thinking about this the wrong way. The charge taper is totally irrelevant. Charging from 65 to 70% will never take longer than charging from 30 to 70% regardless of how much slower the average charge rate is. When you stop at a supercharger you never care how many miles you add, only how much range you need to leave.

Don't just leave it theoretical. Use either EVTripPlanner or ABetterRoutePlanner (both of which take into account charge tapering a superchargers). Plan any trip you want. Do a plan starting the trip at 100% charge and another starting at 75% charge. The 100% charge will result in a shorter trip every time. If you look at how it changes where and for how long you charge it will become apparent why.

 

[David29]

Au contraire, I did include time for both issues:

1) 5-10 minutes was included for “dwell time”
2) time was added since 70mph on the freeway is never 70mph average speed

Ah, well then, I stand corrected. Thank you!

 

[TonyWilliams]

You really are thinking about this the wrong way. The charge taper is totally irrelevant. Charging from 65 to 70% will never take longer than charging from 30 to 70% regardless of how much slower the average charge rate is. When you stop at a supercharger you never care how many miles you add, only how much range you need to leave.

Don't just leave it theoretical. Use either EVTripPlanner or ABetterRoutePlanner (both of which take into account charge tapering a superchargers). Plan any trip you want. Do a plan starting the trip at 100% charge and another starting at 75% charge. The 100% charge will result in a shorter trip every time. If you look at how it changes where and for how long you charge it will become apparent why.

My thoughts on this are not “theoretical”... I’ve actually driven the Model 3 on a 1500 mile trip.

I’ve also driven coast-to-coast in the S-70D, and north-to-south in two different Model S (70D and 90DL) cars (in addition to crazy stuff in much lesser EVs). So, again, I do not find your presumption that 100% charge saves time in the Model 3. In addition, I’ve spell it out in detail as to why. So, if you can point out the “flaw” in my explanation, I’m happy to debate that.

I’m not really following what “65 to 70%” or “30 to 70%” have to do with the debate. Again, the Tesla Model 3 LR will add 150 miles of range in about 20 minutes, if you start from about 50 miles or less when you plug into the Supercharger.

To gain the same 150 miles with 150 miles remaining would take a LOT longer than 20 minutes.

 

[TonyWilliams]

But wouldn't you in that case just skip that supercharger? Certainly my road trip strategy is to always charge to 100% overnight and then drive to the furthest supercharger I can reach. After that I charge to smaller percentages.

I don’t want to keep belaboring this point, but if an overnight charge to 100% puts you at a Supercharger SOMEWHERE down range with about 50 miles remaining, sure, charge to 100%. For the Tesla Model 3 Long Range with new condion battery on a warm day, that is about 250 miles away to maintain a 50-ish mile reserve at 70mph.

We can’t presume that every start has perfectly situated Superchargers, which (again) this is why you want to charge to WHATEVER AMOUNT gets you to the next Supercharger with a low battery state (I’ll just stick with the 50 mile reserve for M3-LR).

Arbitrarily charging to 100% might be what you do, but it’s likely not the fastest traveling time (again, unless there is magically a Supercharger perfectly situated at 250 miles away for the 310 mile range Model 3 LR).

It’s not a problem for me in California, since there are oodles of chargers in any direction I might want to go.

 

[TonyWilliams]

Let’s try some real world examples:

“Tony” has a Model 3 LR with 18” wheels and aero hubcaps, and he wants to travel from San Diego to Las Vegas. It’s 332 miles.

Here are the potential travel times:

5.1 hours (average 65mph)
70 mph cruising speed

San Diego is 238 miles to Baker Supercharger. Nearly perfect for a full charge departure. Just charge enough to complete the next 100 miles, so about 15 minutes.

Total time enroute - 5.1 + 0.25 = 5.35 hours total

*************************

What if Baker Supercharger didn’t exist? (Its only been there a few months). What if Barstow Supercharger (171 Miles) didn’t work? (Yes, happened to me)

In that scenario, I only want enough energy to get to Rancho Cucamonga (113 Miles) for the fastest charge speed. I would plan to depart San Diego with 165 miles of range, so that I can add another 167 miles of range to arrive in Las Vegas with about 50 miles range with about 35 minutes at the Supercharger.

This trip is 20 minutes longer than the first one.

Total time enroute - 5.1 + 0.55 = 5.65 hours total

***********

If I departed with 310 miles of range, and arrived at a charger just 113 miles away, arriving with 195 miles rated range, how long would it take to charge enough to complete 167 miles of travel with 50 miles remaining?

A. 15 minutes
B. 35 minutes
C. Some value far greater than A or B
D. Some value less than A or B

 

[animorph]

Per EVTripPlanner, generic San Diego to Las Vegas, with a stop at Rancho Cucamonga SC, Model 3 LR:

Start at 100% SOC: Total trip time 5:20, 15 min charging, 43 RM remaining.
Start at 60% SOC: total trip time 5:48, 43 min charging, 43 RM remaining.

If you didn't fill to 100% before you started you sat at Rancho Cucamonga SC for an extra 28 minutes.
Why? Because with the 100% start you only needed to add 41 RM at Rancho Cucamonga to make it to Vegas. Starting with 60% you needed to add 157 RM to make it to Vegas. Either way, you're leaving Rancho Cucamonga with 229 RM.

Same is true if you add extra while still eating dinner at the SC. Less rated miles required to be added at the next stop, less time spent at the next stop.

We've done this plenty of times.

 

[animorph]

If I departed with 310 miles of range, and arrived at a charger just 113 miles away, arriving with 195 miles rated range, how long would it take to charge enough to complete 167 miles of travel with 50 miles remaining?

A. 15 minutes
B. 35 minutes
C. Some value far greater than A or B
D. Some value less than A or B

Arriving with 195 miles rated range, you would need to add (167+50) - 195 = 22 RM if we assume a simple RM = 1 real-world mile.
So the answer is A, and much less than 15 min at that. (OK, maybe D then...)

 

[gregincal]

Either way, you're leaving Rancho Cucamonga with 229 RM.

This is the point I was trying to make earlier. You have an state of charge you need when leaving the supercharger to get where you want to go. To get to that state of charge will always take less time arriving with a higher state of charge than arriving with a lower state of charge. In this example you need to get to about 74% full before leaving Rancho Cucamonga. Arriving with 60% state of charge it's going to be kind of slow charging to 74%. If you arrive with 23% you'll get a nice fast charge speed to begin with. But after charging for some amount of time your battery will be 60% full and you still need to charge to 74%. That 60-74% charge will take exactly the same amount of time as if you had arrived with 60%.

 

[TonyWilliams]

Per EVTripPlanner, generic San Diego to Las Vegas, with a stop at Rancho Cucamonga SC, Model 3 LR:

Start at 100% SOC: Total trip time 5:20, 15 min charging, 43 RM remaining.
Start at 60% SOC: total trip time 5:48, 43 min charging, 43 RM remaining.

We aren’t talking about a “generic” trip. It’s a trip with a specific vehicle along a specific route, as an example.

Also, I have no idea what is programmed in EVTripPlanner.

So, next, we will use a longer trip for an example.

 

[gregincal]

We aren’t talking about a “generic” trip. It’s a trip with a specific vehicle along a specific route, as an example.

Also, I have no idea what is programmed in EVTripPlanner.

So, next, we will use a longer trip for an example.

OK, give it a try. Whatever example you come up with, it will still turn out to be faster to start with a 100% charge. EVTripPlanner is very accurate from my experience (you aren't the only person around who has done supercharger road trips).

 

[animorph]

And here I figured a good night's sleep would clear this up.

EVTripPlanner is what I use to plan our long trips. It includes Supercharging taper, which is most of what we're talking about. It optimizes trip times for you, considering routing through Superchargers, driving speeds, and charging speeds. I've found it decently accurate. I used the Model 3 LR as the specific car. The "generic" reference was only for the routing, San Diego to Las Vegas with no specific address given. It's a great way to play "what if". I figured it might lend a little credibility to our statements and provide some concrete details.

We all agree that our normal Supercharging case is to add just enough charge to reach the next charger, with some margin.

Given that we normally arrive at the current Supercharger with that margin already in the battery, we will normally be adding the rated miles required to travel from the current Supercharger to the next. No problem there.

Where we seem to diverge is a special case where you arrive at the current Supercharger with some amount of extra charge, above the normal margin. Tony, my understanding of what you are saying is that you are going to add the rated miles required to travel from the current Supercharger to the next, regardless of the SOC you arrive with. Yes, if you did that with the SOC already above your margin it would end up higher on the taper curve and could take significantly longer than if you started with an SOC right at your margin. But then you would also have more charge than you need to reach the next SC. Assuming we're just waiting for the charge to complete, I think we all agree we don't want to wait while unnecessarily adding extra charge.

So, we need to charge the battery only until it reaches the RM needed to reach the next SC plus the normal margin. That departure target is a specific number of RM's, or battery charge percent. If we arrive at the current SC with SOC exactly at the normal margin, then we add exactly the RM's required to reach the next SC and we're at the departure target SOC. If we arrive at the current SC with extra SOC above the normal margin we only need to add enough RM's/% to reach the departure target. That's the RM's required to reach the next SC minus the extra RM's we arrived with. That will always be faster, at the current SC, than arriving with an SOC exactly at the normal margin.

So, extra SOC arriving at a Supercharger will reduce your wait time at that SC.

The question then is how did that extra SOC get there in the first place?
1) You charged 100% before starting your trip. No time wasted for the extra charge since you hadn't started yet. And you need a little less charge at the first SC, shortening your trip.
2) You spent more time eating dinner, shopping, walking around at a Supercharger than was required for a minimum charge. You let the car keep charging until you were ready to leave, gaining some extra charge (even up to 100%) without delaying your trip beyond you were going to do anyway. You need a little less charge at the next SC, shortening your trip.

Perhaps another point of confusion, just to be clear, the starting SOC at a Supercharger does not determine your charging speed for the whole charge session. The charging taper describes the allowed charging rate at a given instantaneous SOC, regardless of how you got to that SOC. So charging from 19% SOC to 70% SOC always takes longer than charging from 20% SOC to 70% SOC. Starting from 19% has to charge from 19% to 20% first and then perform the same 20% to 70% charge. I suppose charging from 19% might actually charge a little slower from 20% to 70% than actually starting at 20% and charging to 70% if the battery heats up earlier and reduces the charge rate. But that's hopefully not a large effect.

 

[TonyWilliams]

Where we seem to diverge is a special case where you arrive at the current Supercharger with some amount of extra charge, above the normal margin. Tony, my understanding of what you are saying is that you are going to add the rated miles required to travel from the current Supercharger to the next, regardless of the SOC you arrive with. .

No, that’s not what I’m saying.

Obviously, this entire exercise is made far, far easier with really fast recharging at up to 116kW and 310 miles of range!

I’ll continue to treat range and miles driven on a 1:1 ratio, and use 50 miles reserve, with 60 mph average travel speed (one mile per minute). Let’s add 10 minutes dwell time per stop. Let’s stipulate that the Model 3 LR adds:

150 miles in 22 minutes from a low charge state (50 rated miles remaining at start up to 200 rated miles)
150 miles in 49 minutes from 150 rated miles to 300 rated miles

All Superchargers are magically 150 miles apart

*****************

A. 260 mile trip = 260 minutes travel, non-stop, starting from full 100% charge - definitely the fastest to arrive with 50 rated miles remaining at the destination

B. 1010 mile trip = 1010 minutes travel, requiring 1010 - (310 - 50) = 750 miles to be recharged to arrive with 50 rated miles remaining at the destination

Starting the first leg from full 100% charge, then:

If we charge from 50 rated miles at each Supercharger, for a total of 5 times, that’s 5 * 22 = 110 minutes charging
If we charge from 150 rated miles at each Supercharger, for a total of 5 times, that’s 5 * 49 = 245 minutes charging

I presume we are good so far?

(I’m going to dinner)

 

[gregincal]

No, that’s not what I’m saying.

Obviously, this entire exercise is made far, far easier with really fast recharging at up to 116kW and 310 miles of range!

I’ll continue to treat range and miles driven on a 1:1 ratio, and use 50 miles reserve, with 60 mph average travel speed (one mile per minute). Let’s add 10 minutes dwell time per stop. Let’s stipulate that the Model 3 LR adds:

150 miles in 22 minutes from a low charge state (50 rated miles remaining at start up to 200 rated miles)
150 miles in 49 minutes from 150 rated miles to 300 rated miles

All Superchargers are magically 150 miles apart

*****************

A. 260 mile trip = 260 minutes travel, non-stop, starting from full 100% charge - definitely the fastest to arrive with 50 rated miles remaining at the destination

B. 1010 mile trip = 1010 minutes travel, requiring 1010 - (310 - 50) = 750 miles to be recharged to arrive with 50 rated miles remaining at the destination

Starting the first leg from full 100% charge, then:

If we charge from 50 rated miles at each Supercharger, for a total of 5 times, that’s 5 * 22 = 110 minutes charging
If we charge from 150 rated miles at each Supercharger, for a total of 5 times, that’s 5 * 49 = 245 minutes charging

I presume we are good so far?

(I’m going to dinner)

No we are definitely not good so far. Why in the world would you charge from 150 to 300 miles at the first supercharger if it's 150 miles to the second supercharger? At the first supercharger you charge until you have 200 rated miles regardless of whether you arrive with 50 rated miles or 150 rated miles. The amount of time at the first supercharger to go from 150 to 200 is less than to go from 50 to 200 and everything beyond the first supercharger is identical because you are arriving at the second supercharger with 50 rated miles in either case.

Now are we good?