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Discussion Starter #1
Over in this thread, I posted a graph I made that I rather liked, and so I figured I'd share it in its own thread with a few more.

If you want to know roughly what the charging speed will be at different state-of-charge percentages, this bar chart will tell you how long it will take to gain 5% more battery. If you add up adjacent bars, it'll tell you how long it'll take to get a multiple of 5%. For example, if you arrive at a 125A charger at 35% and want to gain 20%, that'll take about 4.2+4.2+4.1+4.3 = 16.8 minutes.



Alternatively, you can use these graphs:

— At a 150A or more DCFC station (e.g., Electrify America's “150 kW” stations):



— At a 125A DCFC station (e.g., good EVgo “50 kW” stations):



— At a 100A DCFC station (e.g., not-as-good EVgo “50 kW” stations):




These graphs are based on @Zoomit's taper-point graphs, GM's battery-voltage table, and empirical measurements of by own. Various caveats apply (battery temp, battery condition, charger manufacturer, etc.) mean that these graphs can never be 100% accurate (although they do closely match @Zoomit's). But they can be useful to get a rough sense of how long to expect different charges to take. It's also fun to build models.
 

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I love your graphs, but I was wondering why you didn't include the 95% to 100% 30 min bar? Don't want to give viewers heart failure? :D Also, I notice that your line graphs show around 20 min to go from 95% to 100%... trust me, it is right at 30 min.

If you would like a charging time calculator I have two versions available in excel format, one that goes by GOM reading, current miles per kWh reading, and desired range, and a simpler one that just uses current SOC and desired SOC. Anyone wants them PM me.

Keith

PS: As you said, you can't show everything, one of the big F U's from Chevy is the limit on charge rate at low battery temperature, and not being able to manually use the battery heater to prep the battery for charging. I will be posting my charts pertaining to charging at an EA 150 amp charger showing the effects of low battery temperature... and this is higher than 50F battery temperature, I don't even want to think about what it is like in Canada in winter!
 

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It would be good to add a legend for the color lines (of there is an easy way to), 0% to 95% in 5% increments if I get it correctly.

Correction, oh, I think I get it now, 10% to 100%, and each color is "read" at the x axis?

The graphs are an interesting view of the changes in slope at onset of taper (>50%?) to worst at 100%. Seems like there might be some table presentation that would be easy to read too, esp. because it's so linear below 50%.

Is this the same relationship that Chevy uses to project time to 80% on the BOLT display?
 

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Discussion Starter #4
Correction, oh, I think I get it now, 10% to 100%, and each color is "read" at the x axis?
Right. If you start at 80% and want to get to 80%, it's going to take you zero minutes to get there, so you can find every target percentage line at its intersection with the x-axis, and then follow it backwards to your actual starting charge and then read off the time.
 

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Discussion Starter #5
Here's three alternative graphs that show charge gained for a chosen number of minutes charging:







Thus if you want to know how much charge you'll get for a 30 minute charge, look at the brown line 6th up from the bottom.
 

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I guess if you live in a ZEV or CARB state this stuff is interesting. The rest of us only imagine a day when DC fast chargers are available on most highways, and are within 100-120 miles of each other, so they can actually be used for a trip.
 

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While I like the charts, one thing to consider is that these are baselines. They do not include times when battery or cabin conditioning are active (a common occurrence), and those systems can easily draw an additional 15 A. Essentially, in real world conditions, 125 A is significantly faster than 100 A up to 70% battery (the chart doesn't illustrate that difference).

I don't have enough sessions with 150+ A chargers to verify all the differences between it and 125 A, but I can say that ~7 minutes faster from 0% to 55% than 125 A is very noticeable on trips. It doesn't quite feel like a brand new car, but it is noticeable.

Considering I typically spend a total of about 2 hours of total charging time over three stops on my regular 500-mile trips, having 150+ A charging would save over 20 minutes of charging time, representing a greater than 20% reduction in time spent charging. Given the way I travel, that would reduce the difference between my trip times in the Bolt EV versus Volt from about 1 hour to maybe 40 minutes. *Disclaimer: this is because I still make my regular dinner stop in my Volt in addition to a fuel stop and bathroom breaks.
 

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I guess if you live in a ZEV or CARB state this stuff is interesting. The rest of us only imagine a day when DC fast chargers are available on most highways, and are within 100-120 miles of each other, so they can actually be used for a trip.
Apparently, that day will come by June of 2019. View restricted to Electrify America sites that are already live or under construction:
 

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Discussion Starter #9
I love your graphs, but I was wondering why you didn't include the 95% to 100% 30 min bar? Don't want to give viewers heart failure? :D Also, I notice that your line graphs show around 20 min to go from 95% to 100%... trust me, it is right at 30 min.
I did include it, in the bar chart; it's the last bar (the one that says 18 minutes). FWIW, my timings in my model match up pretty well with @Zoomit's, by design. I realize it probably doesn't reflect when charging would stop (which would probably indeed by 30 minutes) but I was hopeful that it would be pretty close to when the display would show the car as being at 100%. Perhaps not though. I don't care that much about accuracy at that end of the model because (a) it's a pain to do the final taper/balancing in the model, and (b) no one should ever be charging to 100% at a DCFC anyway (at least not in a situation where they care about time).

If you would like a charging time calculator I have two versions available in excel format, one that goes by GOM reading, current miles per kWh reading, and desired range, and a simpler one that just uses current SOC and desired SOC. Anyone wants them PM me.
I already have two, my own and @Zoomit's. It'd be great for you to share yours too.

PS: As you said, you can't show everything, one of the big F U's from Chevy is the limit on charge rate at low battery temperature, and not being able to manually use the battery heater to prep the battery for charging. I will be posting my charts pertaining to charging at an EA 150 amp charger showing the effects of low battery temperature... and this is higher than 50F battery temperature, I don't even want to think about what it is like in Canada in winter!
Yes, this is captured in the data from the GM app, in the DC_Charging_Profile data. It would indeed be better if they had a preheat option. I think it is a bit complicated though, because the battery also has less capacity when it is cold and it actually takes quite a lot of energy to heat the pack.

Let's assume that the entire pack has a specific heat capacity of 2.7 J/g (a total guess; water is 4.179, iron 0.450, plus there are going to be inefficiencies). 2.7 J/g = 2.7 J/g. That's 2.7 / 3600 = 0.00075 Wh/g and also 0.00075 kWh/kg. The battery pack weighs 440 kG, so that is 0.33 kWh to raise the battery 1 °C. So raising the battery from 15 °C to 25 °C requires 3.3 kWh or 5.5% of your battery. It is still worth it if you have lots of charge left, but it will add about 5 extra minutes to your charge. If it were the case that the car could heat up the battery quickly (e.g., it had a 20 kW battery heater that could get it up to temp in ten minutes) there wouldn't be as much need to preheat. I doubt the battery heater is that powerful, though.
 

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Discussion Starter #10
While I like the charts, one thing to consider is that these are baselines. They do not include times when battery or cabin conditioning are active (a common occurrence), and those systems can easily draw an additional 15 A. Essentially, in real world conditions, 125 A is significantly faster than 100 A up to 70% battery (the chart doesn't illustrate that difference).
Yes, this is totally true. In real-world conditions there are all sorts of caveats. If you're lucky, battery conditioning won't start up until you are past the 67% taper point where all the chargers have power to spare — that's what happened for me when I was charging at a 100A station. For another caveat, my very limited experience, charging at a 100A station actually only gave me 95A (so the charge took longer than indicated in these graphs), whereas the 125A station I used gave me 126A (!!) and got done quicker than expected.

I don't have enough sessions with 150+ A chargers to verify all the differences between it and 125 A, but I can say that ~7 minutes faster from 0% to 55% than 125 A is very noticeable on trips. It doesn't quite feel like a brand new car, but it is noticeable.
The downside of that is that if you get habituated to 150A charging, using a 125A charger will feel as slow to you as 100A chargers do now (even though it's actually not quite as bad).
 

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As the map you display shows, that time does not come in New Mexico next June. Perhaps some year.
That map shows sites where permits are issued and construction has begun. If you want to see all the stations that are planned to be done by next June, including those where the permits aren't issued and only a “rough” (with ten miles) location is given, you want this map:



... which you can easily find on their website. Or instead, you can the attached Google-map version which is perhaps a bit easer to read and see state boundaries.
 

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The downside of that is that if you get habituated to 150A charging, using a 125A charger will feel as slow to you as 100A chargers do now (even though it's actually not quite as bad).
It has already happened.... :crying:

As the map you display shows, that time does not come in New Mexico next June. Perhaps some year.
Those are only the sites that are currently live or under construction (about 40 live and 150 or so being built). As Vertiformed stated, the plans for June of 2019 are far more expansive. I was only including that map to illustrate how much Electrify America has done in just six months. Also, Electrify America seems to be accelerating, but even if they just keep the pace they are currently holding, we should see close to 400 sites operational by June of 2019 with hundreds more sites under construction.

In California alone, we should have seven more of the sites go live by the end of this month, which means we should see even more than that go live across the country in that period. I wouldn't be surprised to see between 80 and 100 Electrify America sites up and running by the end of the year.
 

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I 40 improved, I25 not so much

Looks like in the near future I40 will be pretty well covered. South from ABQ on I25 would still be a problem.😩
 

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Apparently, that day will come by June of 2019. View restricted to Electrify America sites that are already live or under construction:
Yup. I've already laid out the trip for next summer. It still requires a small detour to Elmyra, but not a huge deal. This assumes all chargers work, and are available. Even one problem ends up requiring a night in a motel.
 

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I guess if you live in a ZEV or CARB state this stuff is interesting. The rest of us only imagine a day when DC fast chargers are available on most highways, and are within 100-120 miles of each other, so they can actually be used for a trip.
This is exactly why, at a minimum, every Chevrolet dealership in the country should be required to have at least one green EV spot (outdoors, with 24/7 access) as sacred as a blue handicapped spot), with at least a "faster than L2" Bosch silver box DCFC.

I bet we would even be willing to pay something reasonable to use them. They all come with card readers for possible future use. Heck, they could even require a GM credit card, if that makes a difference. At least it would be a start in the right direction.

Or, somewhat less desirable, Chevy could team up with someone like EVgo an put a real fast charger at most or all dealerships.
 

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Yup. I've already laid out the trip for next summer. It still requires a small detour to Elmyra, but not a huge deal. This assumes all chargers work, and are available. Even one problem ends up requiring a night in a motel.
If EA reliability to date is any indication, prepare for a night in a motel :)

Keith
 

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Yup. I've already laid out the trip for next summer. It still requires a small detour to Elmyra, but not a huge deal. This assumes all chargers work, and are available. Even one problem ends up requiring a night in a motel.

...with either a destination EVSE, or a ground-floor room with a window that opens and an outlet/circuit that can handle another 12A. That 12A is still only going to get you ~70 miles of range overnight (12Hrs).

That "one problem" could devastate vacation plans. It's similar to a coast-to-coast flight, with a layover at DFW. Always allow at least two hours between flights. The variable weather in Dallas has spoiled many connections, and the extra margin can yield dividends.

If I were driving the Bolt across country, with a hard arrival date at the other end, I'd build a couple extra days into the schedule for charging layovers. FWIW, I wouldn't even attempt this until 2020, but I'm a belt and suspenders kind of guy.
 
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