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Discussion Starter #1




I think I mentioned it in another thread, but there's a free (as in beer) 100kW DCFC near my home that I've been using for the past 3 months or so. It'll turn into a paid station soon, but not before getting these neat charging graphs out of it. Charger doing 150A from the get-go was something I hadn't witnessed before, but apparently it can happen with the right battery temperature - around 25 to 26C.

I've made some analysis in my blog post, but I think much of the stuff are self-explanatory. We have the voltage creeping up, the current staggering down in steps (50% - 67% - 83% - 92% - 98%), the battery heating up at 150A charging and then subsequently cooling thanks to a lower ambient temperature, and the SoC curves doing a nice slope against the charging time.
 

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Interesting.

In the video below (also max speed charging), the Bolt tapers at 70%, whereas in your graph (and some other graphs too) it tapers at 67%. I wonder what governs this...

 

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Interesting.

In the video below (also max speed charging), the Bolt tapers at 70%, whereas in your graph (and some other graphs too) it tapers at 67%. I wonder what governs this...
Looks like the tapering occurs right when the battery temp hits 34C. Guessing this would be the variable that triggers the tapering.
 

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In the video below (also max speed charging), the Bolt tapers at 70%, whereas in your graph (and some other graphs too) it tapers at 67%. I wonder what governs this...
I'm curious about this as well. All the videos I've seen of 150A DCFC have shown tapering at 55% and not at 50%. Maybe it's a temp thing, as stated? But that would only explain the taper at 50%, not the 67% (instead of 71%). Maybe conditions were not optimal?
 

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Looks like the tapering occurs right when the battery temp hits 34C. Guessing this would be the variable that triggers the tapering.
I trust all of the data on that screen except for the battery SOC percentage. It seemed to read a bit high, as noted in the accompanying article linked in the YouTube video description.

This was not a final product version of the software and this screen was designed for test engineers. The SOC may have been calculated by the charger dispenser instead of displaying the value supplied by the car. I don’t know.
 

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My Bolt has always tapered at around 50% and 67% on DCFC, and I am jealous of those who get to 55% and 70+% before tapering. I would think it was a temperature issue, but Eric (NewsCoulomb) drives his car pretty hard, so I doubt his battery pack is nice and cool when he starts a charge, and he gets the later taper points than me on a normal basis.

Keith
 

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I trust all of the data on that screen except for the battery SOC percentage. It seemed to read a bit high, as noted in the accompanying article linked in the YouTube video description.

This was not a final product version of the software and this screen was designed for test engineers. The SOC may have been calculated by the charger dispenser instead of displaying the value supplied by the car. I don’t know.
The battery SoC is communicated by the car to the station. Even if it were possible to use other information supplied by the car (e.g., voltage demanded) to try to guess SoC, there would be zero reason to do so when the correct information is already provided as part of the protocol.
 

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The battery SoC is communicated by the car to the station. Even if it were possible to use other information supplied by the car (e.g., voltage demanded) to try to guess SoC, there would be zero reason to do so when the correct information is already provided as part of the protocol.
Yes, I know. Yet, the SOC on the charger display was inconsistent with the car’s own app readout after charging was ended. I’m not saying it makes sense, just that I observed it. It’s possible that whoever wrote the test data screen didn’t know what they were doing and rolled their own SOC calculation based on the measured energy dispenser from the charger rather than just displaying the SOC values sent by the car. That was my best guess.
 

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Discussion Starter #9
My Bolt has always tapered at around 50% and 67% on DCFC, and I am jealous of those who get to 55% and 70+% before tapering. I would think it was a temperature issue, but Eric (NewsCoulomb) drives his car pretty hard, so I doubt his battery pack is nice and cool when he starts a charge, and he gets the later taper points than me on a normal basis.

Keith
I had my Bolt charged under all sorts of temperature conditions, and I've consistently gotten tapering at around 50% and 67% mark. It never extended to 55% or 70+% once. One possibility that could let this could happen is if the Bolt's BMS changed its mind about (i.e. reassessed) the battery SoC value mid-charge. But if this happens consistently for certain Bolts, then I'm curious to know what the actual cause is.
 

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It’s possible that whoever wrote the test data screen didn’t know what they were doing and rolled their own SOC calculation based on the measured energy dispenser from the charger rather than just displaying the SOC values sent by the car.
I really think that's just not possible. I'm not sure that the charger would even have the information needed to make a guess. How would it guess initial SoC? How would it guess battery capacity?

That was my best guess.
I think you need a better guess. FWIW, I'd trust the charger over information from the app, which is often out-of-sync with reality (plus has different rounding behavior).
 

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I really think that's just not possible. I'm not sure that the charger would even have the information needed to make a guess. How would it guess initial SoC? How would it guess battery capacity?
It seems almost certain that the charger started off with an initial SOC value from the car. The question is whether the later SOC updates on the test data screen were based on newer SOC messages from the car or were updated based on the energy sent from the charger to the car.


I think you need a better guess. FWIW, I'd trust the charger over information from the app, which is often out-of-sync with reality (plus has different rounding behavior).
The discrepancy between app and charger display at the end of the charging session is too large to be easily explained away. The charger reports 97% full but the app says 88%. In any case, the charger SOC should not be assumed accurate without further testing. That test screen is probably no longer available on that one unit installed at ChargePoint’s HQ although I haven’t been there recently. It wasn’t meant to be a product-quality user interface screen for regular users.

I have found the app SOC value to be consistent and credible when properly synced with the car.
 

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Discussion Starter #12
Just to throw in my experience, displayed SoC values have always been agreement between the car’s dashboard (bar moving at the exact 5% level), the MyChevrolet app (1% resolution), and the OBD-II sensor output (0.4% resolution). So they are apparently all working with the same data source. Also, the public chargers I used had the displayed SoC value that was in sync with the aforementioned value with a delay of a couple of seconds.
 

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That test screen is probably no longer available on that one unit installed at ChargePoint’s HQ although I haven’t been there recently. It wasn’t meant to be a product-quality user interface screen for regular users.
If the charger was the 62.5 kW unit named Chargepoint HQ 41 on East Hacienda, I used it for the first time over the weekend w/my Bolt. Juice was free. :) It still has the bar at the bottom (Diagnostics, Slac, etc.)

When trying to stop my session (I took off when I tapered to ~27 kW (was expecting ~24 kW)), I recall the stop button on the UI not working and seeing screen full of debug info. I think I ended up either swiping my card again or using ChargePoint's app to stop. There was an e-Golf guy waiting and I didn't really need the juice anyway.

Sorry. I didn't bother comparing the % SoC.
 

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It seems almost certain that the charger started off with an initial SOC value from the car. The question is whether the later SOC updates on the test data screen were based on newer SOC messages from the car or were updated based on the energy sent from the charger to the car.



The discrepancy between app and charger display at the end of the charging session is too large to be easily explained away. The charger reports 97% full but the app says 88%. In any case, the charger SOC should not be assumed accurate without further testing. That test screen is probably no longer available on that one unit installed at ChargePoint’s HQ although I haven’t been there recently. It wasn’t meant to be a product-quality user interface screen for regular users.

I have found the app SOC value to be consistent and credible when properly synced with the car.
Do you have hill top reserve set? The Bolt MAY (not saying it does this) report initial SOC and total capacity at the start of a charge... if you have HTR set it MAY report 53 KW as total battery capacity... just a thought.

Keith
 

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Do you have hill top reserve set? The Bolt MAY (not saying it does this) report initial SOC and total capacity at the start of a charge... if you have HTR set it MAY report 53 KW as total battery capacity... just a thought.

Keith
Interesting idea. I think I did have it set. However, I’m skeptical that it would work that way.
 

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Further evidence.... I just recently noticed that my charging video shows the car drawing around 16 kW at “97%” state of charge. That’s very unlikely but would be consistent with a state of charge of around 88%. At a real SOC of around 95-97% the car would have reduced charging down to 7-11 kW based on my past observations.
 
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