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Discussion Starter #1
I've been refining my Bolt EV charging models and, with recent 100kW DCFC data from Norway, I now have a better set. These graphs may help people understand the Bolt EVs DC fast charging performance. It's important to note that these models assume optimal conditions; which are rare for us to normally experience due to factors like battery starting temperature, ambient temperature, and some charging cycles limited to 30 min; so our charging times will be a little bit longer.

For reference:
125A is a typical "50kW" charger and most pervasive
100A is sometimes called a 50kW charger but EVs stop charging around 400V so our cars would never see 50kW from them.
60A is a 24kW charger

Also, the 125A charging model shows that 90 EPA miles are gained in 32 minutes and 160 EPA miles are gained in 59 minutes. Compare this to the GM-stated DCFC performance on Chevy EV Life:

"Up to 90 miles of range in about 30 minutes of charge"
"DC Fast Charging will restore up to 160 miles in about an hour"

It seems that under optimal conditions, those specs can be met with a 125A charger.







 

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Well this certainly explains why I only got 13KW added to my battery when I hooked up for 30 minutes at a 50KWH Fast DC charger at 68% charge.
Start of Charge had 68%, 30 minutes later at the end of charge had 80% Charge.
 

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Thanks for posting these graphs. I conclude that there is little advantage of using the more powerful EVSE Fast "Chargers" if you just want to "top off" from say 70% to 95%. Is this correct?

Jeff
 

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Discussion Starter #4
Well this certainly explains why I only got 13KW added to my battery when I hooked up for 30 minutes at a 50KWH Fast DC charger at 68% charge.
Start of Charge had 68%, 30 minutes later at the end of charge had 80% Charge.
Your numbers seem off. 13kWh is a 22% gain. Did it start at 58% or end at 90%.

Either way, yes, you will certainly see less energy gain at higher battery levels.
 

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Discussion Starter #5
Thanks for posting these graphs. I conclude that there is little advantage of using the more powerful EVSE Fast "Chargers" if you just want to "top off" from say 70% to 95%. Is this correct?

Jeff
That's correct. The 24 kW (60A) DC fast chargers are just as effective as the higher power ones when the battery is ~70% or higher. 70% is 14 of 20 green bars.
 

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It may have been 85% when it was done and the amount of 13KW was what I remember the Charging company said it was, I may not have correctly remembered that value.
 

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Do you have a reference for the 100kw DCFC Norway data? I haven't been able to find any yet myself. MANY thanks for putting the work in on these graphs, they are so useful for long trip planning!
 

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Discussion Starter #8
Do you have a reference for the 100kw DCFC Norway data? I haven't been able to find any yet myself. MANY thanks for putting the work in on these graphs, they are so useful for long trip planning!
From a Norwegian forum: https://translate.googleusercontent.com/translate_c?act=url&depth=2&hl=en&ie=UTF8&nv=1&prev=_t&rurl=translate.google.com&sl=auto&sp=nmt4&tl=en&u=https://elbilforum.no/forum/index.php/topic,31392.msg600660.html?PHPSESSID=afh05imvbl3olvts0tn3bo47c2&usg=ALkJrhiU0x9fRhJ5x47iP9MIohsDFMJ7qg#msg600660
 

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I don't know how you found that, but two thumbs up from me! Now if we can just get some American investment in similar infrastructure...
 

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From a Norwegian forum:
Interesting - he's seeing it peak out at around 55kW of power. That's a little better than we've seen with the local 50kW chargers (which top out in the high 40's due to the current limitation), but not earth-shatteringly so.
 

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Discussion Starter #11
Correct, charging at 55kW is not much different than at 45kW. See graphs above. For a 30-min charge session, when starting below ~15% battery level, the car only gains about 15 more miles. So when >125A chargers start becoming available, it won?t likely be worth going out of your way to use them as opposed to the common 50kW/125A units.
 

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Correct, charging at 55kW is not much different than at 45kW. See graphs above. For a 30-min charge session, when starting below ~15% battery level, the car only gains about 15 more miles. So when >125A chargers start becoming available, it won?t likely be worth going out of your way to use them as opposed to the common 50kW/125A units.
However, when you have an impatient spouse and/or kids in the back, every minute counts! ;)
 

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Just out of curiosity, I may have missed the answer, but are these 'actual' charging sessions that these numbers are coming from?
Or is this the company's rendition on what one should get with the Bolt?

Great graph BTW,

We need Stickies on this forum.
 

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These were extrapolated from the available charging current for the given DCFC, and multiplied by the charge voltage vs state of charge slope expected for the vehicle, people are capturing voltages from the OBD2 port. The step downs are gleaned from first hand accounts I think, and not published engineering data. It's all "ideal condition" EPA-range results, in particular pack temperature will play a role in people's actual results.
 

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I've been refining my Bolt EV charging models and, with recent 100kW DCFC data from Norway, I now have a better set. These graphs may help people understand the Bolt EVs DC fast charging performance. It's important to note that these models assume optimal conditions; which are rare for us to normally experience due to factors like battery starting temperature, ambient temperature, and some charging cycles limited to 30 min; so our charging times will be a little bit longer.

For reference:
125A is a typical "50kW" charger and most pervasive
100A is sometimes called a 50kW charger but EVs stop charging around 400V so our cars would never see 50kW from them.
60A is a 24kW charger

Also, the 125A charging model shows that 90 EPA miles are gained in 32 minutes and 160 EPA miles are gained in 59 minutes. Compare this to the GM-stated DCFC performance on Chevy EV Life:

"Up to 90 miles of range in about 30 minutes of charge"
"DC Fast Charging will restore up to 160 miles in about an hour"

It seems that under optimal conditions, those specs can be met with a 125A charger.

OK. I just did a DCFC from a '125A charger', the EVGo one in Brooklyn. I had the car parked in an underground garage, so the pack was 'warm' (the car was like 70°F when I got into it, without preconditioning).

With the above graph in mind, I watched the power versus SOC carefully. I saw all the same 'steps'...from 42-44kW to 37-38 kW to 24-25 kW. BUT, the step from 42 to 38 occurred at 60% SOC and the step from 38 to 25 was at 75% SOC, and then it started ramping down hard right around 80%. All in all, quite a bit more reasonable than the graph above.

I was watching the dash display (each bar = 5% SOC) and comparing to the display on the DCFC, which had a percentage to 1 %. I **think** the dash display ROUNDS. That is 80% reading (16 bars) is 77.5 to 82.5%.

The above steps in SOC were taking this into account.

I went from 20 to 79% SOC (36 kWh nominal) in 55 minutes.
 

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I was watching the dash display (each bar = 5% SOC) and comparing to the display on the DCFC, which had a percentage to 1 %. I **think** the dash display ROUNDS. That is 80% reading (16 bars) is 77.5 to 82.5%.
Dash display definitely rounds UP based on what I have seen. So as soon as it is above 45%, it will show 50% half charge for example. I noticed that while watching the DCFC stats. 46% on charger had the dash bar at 1/2 full.
 

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Dash display definitely rounds UP. So as soon as it is above 45%, it will show 50% half charge for example.
I've noticed the same behavior, as soon as SOC-gauge hits the bottom of the bar's range, it illuminates exactly as you describe.
 

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Discussion Starter #18
Right--all 20 bars are shown until 5% (3kW) is burned off. Similarly, when the last bar disappears, you're out, it's at 0%.
 

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I wouldn't call it "rounding up" - it i just a visible indicator of range. There are 20 bars, each bar indicates being somewhere in a 5% range. The first bar is 0-5%, the second is 5-10%, the third is 10-15%, etc.
 

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I wouldn't call it "rounding up" - it i just a visible indicator of range. There are 20 bars, each bar indicates being somewhere in a 5% range. The first bar is 0-5%, the second is 5-10%, the third is 10-15%, etc.
But that's not what people expect. It should do the opposite -- show me 10 of 20 bars means that I'm at least half full.

Not that it really matters around the middle, but it does when you're getting low. There's a huge difference between seeing 2 bars (10-15%) and seeing 3 bars (10-15%) range. In the driver's mind, that's 50% extra range in the second case.
 
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