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Discussion Starter #1
When I planned my most recent trip with the Bolt - 480 miles over 2 days from San Jose, CA to central Humboldt county and back mostly on US 101 - I did some back-of-envelope calculations to estimate how much time one would expect* to spend driving vs/charging. It went something like this:

1) Averaging 60 mph, at 4 mi/kwh (EPA range estimate), battery depletes at a rate of ~25%/hour.
2) GM advertises up to 90 miles in 30 minutes. This equates to 45kw. So replacing that 25% of charge (60 miles) equates to 20 minutes charging.
3) If you start the trip off nearly full, and finish 1/4 full, then the first 3 hours (180 miles) are essentially 'free' in terms of extra time spent charging.

So for my 480 mile trip, that should equate to 8 hours of driving, and 1h40 in charging to gain 75kw.

In practice, things worked out a bit differently. I did in fact average 60 mph and a bit more than 4 miles/kwh, and put in exactly 76kw. I charged 4 times, always starting below 50%, never ending above 80%. But I spent 2h25 to do so (45 minutes longer than the estimate).

The reasons why it took so much longer are not complicated. To be fair it was not really a surprise to me (or likely anybody who reads these forums regularly), but I think they're worth mentioning, particularly given the number GM advertises: I never reached 45kw charge rate during any charging session and I averaged 32kw overall. Possible reasons:
1) Charging stations not capable of delivering 45kw. Not an issue in my case (all were 50kw+) but many 'fast' chargers are not that fast.
2) Battery/outside temperatures causing throttling. I don't think this played much of a role for me - temperatures were 55-75 degrees out and batteries were warm in all cases (70 degrees) - but I can't be sure.
3) Battery SoC causing tapering. I did see some of this. Although all charging sessions started below 50%, there is some modest tapering at 55%.

In short - even under good conditions, it's probably more realistic to expect 30 minutes/25% charge. I'm doing a 420 mile trip next week (over one day). I plan to spend 2h-2h30 charging (in addition to 7 hours of driving).

*Note that I had gone through Vertiformed's excellent time-to-charge graphs before the trip, so I was aware that GM's numbers are grossly optimistic, if not downright misleading.
 

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Anecdotally, I understand the the optimal way to travel in a Bolt is to stay in the bottom 50% of state of charge to minimize tapering and cost for per minute DCFC. I've only FC once to familiarize myself with it and achieved 36 kWh/hr charge (EVGO 50 kWh). I'll get more practice next month during a trip to Mt St Helena from San Ramon (Bay Area). If you can find a 150 kWh charger (EA), theoretically can charge up to 55 kWh up to 55%.
 

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Discussion Starter #3
Yes, this is the way to minimize charging time. But the devil is in the details. I tested out a 150kw station a few weeks back (40% starting SoC) and got my usual 37kw speed. Maybe it was too cold (55 degrees)? I can only guess the reason since the Bolt doesn't say.

Also staying in the bottom 50% requires regularly spaced stations that are in good working order. I effectively did that for most of my trip, but I was taking a chance - there was one leg with only a single CCS DCFC - had that gone down I would have had a very long night.

Unless you are taking significant detours or driving well above 60mph, you should be able to get from San Ramon to Mt. St. Helena and back on one charge without difficulty.
 

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You said all the stations were “50kw+”, but I suspect that that doesn't mean what you think it meant. A station claiming to be 50 kW only means it can deliver 50 kW to some (mythical) EVs, not that it can actually deliver 50 kW to a Bolt.

In particular, there are stations that are limited to 100 amps. These stations can only deliver 50 kW if they're providing 500 volts (i.e., 500 volts × 100 amps = 50,000 watts = 50 kW).

During a charge between 5% and 80%, the Bolt is likely to be asking for voltages in the range 325–380V, and is capable of drawing up to 150A (until the first taper occurs, which is at a voltage of about 365 V), so this means that on a 100A station that represents itself as a “50 kW” station, charging can begin as low as 32.5 kW and will reach the first taper point at only 36.5 kW. That said, on such a low power charger, the first taper will be invisible and it will continue increasing in charge rate until it hits the second taper point at 70%, when at best the voltage will be 375V.

There are also a lot of 125A stations. They can deliver 50 kW at 400V, but again that doesn't match up at a Bolt's needs. They'll deliver 40.625 kW with an almost empty battery, rising to 45.6 kW at the first taper point.

Even more powerful stations hit the 150A limit of the Bolt itself. For an almost empty battery, they deliver only 48.75 kW, rising to 54.67 kW just before the first taper (which cuts the charging rate to 100A).

I think in your case, a mix of arriving with a high state of charge and using 100A and 125A stations that purported to be “50 kW” stations (for mythical EVs that don't actually exist) may explain much of your disappointment with charging rates.
 

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BTW, here's a tip when traveling. When you stop at a new (to you) DCFC station, find the model/specifications plate on the charger (it's always somewhere) and take a photo. Share that on PlugShare (unless it's there already, which it rarely is). This photo lets other people on PlugShare see just how fast the charger can actually go (and in particular, whether it is a craptastic 100A charger).
 

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The battery heater goes off at 64F, the temperature at which you get 110 amps out of a high power DCFC, from there the battery temperature slowly goes up due to the charging current itself. When battery pack temp gets over 75F you will be able to achieve full charging speed... but in really cold weather by this point you are probably near or past the first taper point.

Also, your first taper point only drops you down from 54ish KW to 37ish KW, but the next taper point around 66% SOC nose dives down to 24 KW... so any time you are charging past 66% be ready to wait for a while. You said you didn't go past 80%... good thing, charging rate gets really grim up there. From 81% to 91% you are at 16 KW. Then from 91 to 95% you are at 11 KW. From 95% to 100% it enters the constant voltage zone, so as SOC rises amperage has to decrease, and you get a linear fall from 10 KW to 0 KW during that last 5%

Keith
 

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Discussion Starter #7
Thanks Veriformed and Fivedoor. Excellent points. I also hadn't considered the voltage/amperage limitations closely - yes 100A at 380V (which is what my OBD-II reader reported) is only 38KW which is what I saw on several instances. One of the stations did claim to be 62.5KW. I'll have to measure more carefully (and take pictures).

Do you folks have any suggestions where I can read the details on battery temperature vs. current allowance on the Bolt? Thanks!
 

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Thanks Veriformed and Fivedoor. Excellent points. I also hadn't considered the voltage/amperage limitations closely - yes 100A at 380V (which is what my OBD-II reader reported) is only 38KW which is what I saw on several instances. One of the stations did claim to be 62.5KW. I'll have to measure more carefully (and take pictures).

Do you folks have any suggestions where I can read the details on battery temperature vs. current allowance on the Bolt? Thanks!
This Reddit post had a goldmine of data, taken directly from a file that is part of the myChevrolet app. It's in JSON format, if you're familiar with that (if not, the formatting is still pretty easy to follow and extract data from).

It's not perfect (and you may be able to find your own versions of some things via ODB-II) but I see it as pretty awesome.
 

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Also, your first taper point only drops you down from 54ish KW to 37ish KW, but the next taper point around 66% SOC nose dives down to 24 KW... so any time you are charging past 66% be ready to wait for a while. You said you didn't go past 80%... good thing, charging rate gets really grim up there. From 81% to 91% you are at 16 KW. Then from 91 to 95% you are at 11 KW. From 95% to 100% it enters the constant voltage zone, so as SOC rises amperage has to decrease, and you get a linear fall from 10 KW to 0 KW during that last 5%

Keith
This is where time-based-charging chargers are a problem. It becomes less economical to spend the time charging after various tapers.
 

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This is where time-based-charging chargers are a problem. It becomes less economical to spend the time charging after various tapers.
Yup. This is why on long trips I try to never charge past 66%, my 3000+ mile round trip this summer cost me half of what it would have cost me to do the same trip in my Miata, because I am a "plus" member on Electrify America. Without the savings from the membership it would have broke even with the Miata cost to do the trip.

Too bad many states outlaw selling power by the kWh if you are not a utility company.

Keith
 

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Yup. This is why on long trips I try to never charge past 66%, my 3000+ mile round trip this summer cost me half of what it would have cost me to do the same trip in my Miata, because I am a "plus" member on Electrify America. Without the savings from the membership it would have broke even with the Miata cost to do the trip.

Too bad many states outlaw selling power by the kWh if you are not a utility company.

Keith
I only know of two that I've come across in my general geographic area that I drive. They're run by a utility known more for its NG supply than power but they do have some territory for power. The other charging chargers are run by another utility known more for power and do in fact charge for power, not time.
So the first guys suck.

(BC Canada - FortisBC and BCHydro) (flo operates the FortisBC ones and Greenlots the BCHydro ones)
 

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1) Averaging 60 mph, at 4 mi/kwh (EPA range estimate), battery depletes at a rate of ~25%/hour.
2) GM advertises up to 90 miles in 30 minutes. This equates to 45kw. So replacing that 25% of charge (60 miles) equates to 20 minutes charging.
3) If you start the trip off nearly full, and finish 1/4 full, then the first 3 hours (180 miles) are essentially 'free' in terms of extra time spent charging.

So for my 480 mile trip, that should equate to 8 hours of driving, and 1h40 in charging to gain 75kw.

In practice, things worked out a bit differently. I did in fact average 60 mph and a bit more than 4 miles/kwh, and put in exactly 76kw. I charged 4 times, always starting below 50%, never ending above 80%. But I spent 2h25 to do so (45 minutes longer than the estimate).

The reasons why it took so much longer are not complicated. To be fair it was not really a surprise to me (or likely anybody who reads these forums regularly), but I think they're worth mentioning, particularly given the number GM advertises: I never reached 45kw charge rate during any charging session and I averaged 32kw overall. Possible reasons:
Huh? You have some unit confusion in your OP.

miles/kWh is correct. For #2, "45kw", huh? Energy is measured in kWh, not "kw". Charging (and discharging) rate is measured in kW. If you had a 6 kW device that ran for 1 hour, it used 6 kWh. If it ran for 2 hours, it used 12 kWh.

As for "75kw" and "76kw", you talking about 75 and 76 kWh?

The car's instrumentation uses the right units.
Too bad many states outlaw selling power by the kWh if you are not a utility company.
Correct. It's not that uncommon in the US and was more common back in the early days of our current generation of EVs (beginning Dec 2010 w/gen 1 Leaf).
 

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Discussion Starter #13
Huh? You have some unit confusion in your OP.

miles/kWh is correct. For #2, "45kw", huh? Energy is measured in kWh, not "kw". Charging (and discharging) rate is measured in kW. If you had a 6 kW device that ran for 1 hour, it used 6 kWh. If it ran for 2 hours, it used 12 kWh.

As for "75kw" and "76kw", you talking about 75 and 76 kWh?
You're correct on both accounts - those are kWh.

Regarding charging costs, I've found that being able to use an L2 overnight to charge from 20% to 100% makes a huge difference. Unfortunately they're not always available. (Even in the Bolt's sweet spot at EvGo's reduced rates and a 45kw rate, it winds up being around $5.50 for 60 miles, which is more than what fuelling up a Prius costs for the same mileage.)
 

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(Even in the Bolt's sweet spot at EvGo's reduced rates and a 45kw rate, it winds up being around $5.50 for 60 miles, which is more than what fuelling up a Prius costs for the same mileage.)
What you stated at the end is a big reason why when I bought my used '13 Leaf, I elected not to pay extra for a used one with CHAdeMO inlet. I wrote about it at https://www.mynissanleaf.com/viewtopic.php?p=519701#p519701. Back then, EVgo was a lot more money.

My former 06 Prius was my "range extended" when my '13 Leaf didn't cut it. EPA range rating on a full charge and new battery was 84 miles.
 
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