GM Volt Forum banner

1 - 20 of 20 Posts

·
Registered
Joined
·
6,464 Posts
Discussion Starter #1 (Edited)
I had the chance to record an ideal charging session on an EVgo 125 A charger. This session started at 20% and ended at 50% SOC. Based on what we know, this should be the fastest possible charging window for the Bolt EV on a 125 A charger. It was humid, the temperatures were around 60 F, and the battery was warm from driving.

The 30 minute session resulted in ~22.5 kWh, or an average charge rate of 45 kW. Unfortunately, I was unable to get my OBD2 adapter to work and log the charge.

 

·
Premium Member
Joined
·
14,156 Posts
Very helpful. Seems like it's right on spec. My guess is you wan't be able to charge any faster from a 150 kW station. I'm also thinking you meant "unable to get" rather than "able to get".
 

·
Registered
Joined
·
6,464 Posts
Discussion Starter #3
Very helpful. Seems like it's right on spec. My guess is you wan't be able to charge any faster from a 150 kW station. I'm also thinking you meant "unable to get" rather than "able to get".
Thanks for catching the typo.

As for the charging speed, I actually disagree. I have a hard time believing that GM limited the max current to 125 A, especially because we have video footage of them testing the Bolt EV on a 175 A charger. I've built out a couple of predictive models of the Bolt EV's charge curve, and one of them almost identically matches with pretty much everything that GM has publicly stated regarding the charge rate (i.e., 50 kW average charge rate to 80%, 60 kW peak rate, 80 kW charger required for max charge speed).
 

·
Registered
Joined
·
13,940 Posts
Thanks for catching the typo.

As for the charging speed, I actually disagree. I have a hard time believing that GM limited the max current to 125 A, especially because we have video footage of them testing the Bolt EV on a 175 A charger. I've built out a couple of predictive models of the Bolt EV's charge curve, and one of them almost identically matches with pretty much everything that GM has publicly stated regarding the charge rate (i.e., 50 kW average charge rate to 80%, 60 kW peak rate, 80 kW charger required for max charge speed).
Thanks for doing all this analysis in the interest of science. Most of us would just plug it in and drive.
 

·
Registered
Joined
·
2,038 Posts
What is the kW charge rate that this charger is rated at? Is it a 50 kW charger that in the real world sees 45 kW charging? Do different 125 amp chargers charge at the same rate? Or are all or most 125 amp chargers rated at the same kW charge rate?
Sorry for the basic questions, but I am realizing I know less about chargers than I thought I did.

I have always thought of chargers by their kW charge rate, i.e. my Volt tops out at 3.3 kW charging, but there are 22 kW chargers out there for BEV's and many of us are now hoping for DCFC at 75 kW chargers in an area near you. Next year, or the year after, maybe 150 kW charging will start to show up...
 

·
Banned
Joined
·
7,289 Posts
The 100A stations advertised as "50 kW" are really a sham. There is not a single EV in existence that could actually charge at 50 kW at one of those stations. The 50 kW rating is purely theoretical.
 

·
Registered
Joined
·
1,340 Posts
The 100A stations advertised as "50 kW" are really a sham. There is not a single EV in existence that could actually charge at 50 kW at one of those stations. The 50 kW rating is purely theoretical.
My Model S can, with the CHAdeMO adapter. I did it several times on a trip from TX to TN. I even charged at Nissan's US HQ, at that rate. It's all about the voltage. ;)
 

·
Registered
Joined
·
5,431 Posts
Nice news to read. As LG Chemical gains more real life data from their batteries and cells installed in EVs, and also gain data from GM vehicle feedbacks, they can continue to improve the cell chemistry and design to allow higher charging currents without damaging the cell or shortening its life. I have seen how the cell technology has improved in twenty years (when the first Li-ion cells came out), so by 2030 we will see more improvements, and finally see the 400+ mile range BEV for less than $35,000 which can displace all the remaining ICE vehicles.
 

·
Banned
Joined
·
7,289 Posts
My Model S can, with the CHAdeMO adapter. I did it several times on a trip from TX to TN. I even charged at Nissan's US HQ, at that rate. It's all about the voltage. ;)
I really doubt your Tesla can charge at 50 kW at a *100 AMP* station. Unless your Tesla is special and has a nominal 500 volt battery.
 

·
Registered
Joined
·
878 Posts
re: GM's charge rate claims. I seem to recall that someone technical from GM (Josh Tavel? Pam Fletcher?) said the Bolt could charge up 90 miles in a half-hour and 160 miles in an hour. With 60 kWh of battery and 238 miles of range, that is 4 miles per kWh. At 22.5 kWh in a half-hour, that is exactly 90 miles. It supposedly would then charge another 70 miles in the next half-hour, which would be 17.5 kWh and a 35 kW average charge rate. I'm thinking it is maxed at a 125A charger, with everything optimal. They might have validated the hardware for higher rates, but they may have software-limited the current model year to 125A.
 

·
Banned
Joined
·
7,289 Posts
re: GM's charge rate claims. I seem to recall that someone technical from GM (Josh Tavel? Pam Fletcher?) said the Bolt could charge up 90 miles in a half-hour and 160 miles in an hour. With 60 kWh of battery and 238 miles of range, that is 4 miles per kWh. At 22.5 kWh in a half-hour, that is exactly 90 miles. It supposedly would then charge another 70 miles in the next half-hour, which would be 17.5 kWh and a 35 kW average charge rate. I'm thinking it is maxed at a 125A charger, with everything optimal. They might have validated the hardware for higher rates, but they may have software-limited the current model year to 125A.
But if that's the case (max charging capped at 125 amps), why does the Bolt's manual quote using an 80 kW DCFC station? If the Bolt can attain the "90 miles in 30 minutes" at a 50 kW station?

Anyways, I have sources that tell me if the Bolt is plugged into a >125 amp station, the Bolt can take advantage of that extra juice. ;)
 

·
Registered
Joined
·
1,489 Posts
They might have validated the hardware for higher rates, but they may have software-limited the current model year to 125A.
It's just as likely that they simply quoted rates achievable on the chargers actually available to the public. It would have been pretty bad publicity for them to quote charging rates that nobody could actually achieve in practice due to a lack of capable chargers.

We're not going to know for sure one way or the other until someone's able to charge at a charger with a substantially higher capacity than 125A.
 

·
Registered
Joined
·
3,193 Posts
Nice it clearly shows that the peak charging rate at 125A exceeds 45KW for a portion of the charge.

If the original Model S 60 is any indication I too think the Bolt EV at about 20% SOC will take 175A and possibly 200A for a short period of time before tapering. We will know soon enough as Ampera-e's will be delivered in Norway very soon and they have 100KW 200A CCS units there. The Bolt EV manual does state a maximum charge rate of 80KW.

What is the kW charge rate that this charger is rated at? Is it a 50 kW charger that in the real world sees 45 kW charging? Do different 125 amp chargers charge at the same rate? Or are all or most 125 amp chargers rated at the same kW charge rate?
Sorry for the basic questions, but I am realizing I know less about chargers than I thought I did.

I have always thought of chargers by their kW charge rate, i.e. my Volt tops out at 3.3 kW charging, but there are 22 kW chargers out there for BEV's and many of us are now hoping for DCFC at 75 kW chargers in an area near you. Next year, or the year after, maybe 150 kW charging will start to show up...
A station with a 50KW name plate rating will either mean 50KW at 500VDC and 100A (Power (KW)/1000 = Voltage (V) X Current (A)). Or it will mean 400VDC at 125A.

The Bolt EV has a nominal pack voltage of 344VDC. So it's charge voltages are below 400VDC. So even if you charge at the station maximum of 125A you will not hit 50KW due to the lower charge voltage. Currently there are no BEV's on the market that charge above 400VDC (that use CCS or CHAdeMO). Though there are some planned.

However looking at the charge curve the Bolt EV maxes out a 125A charger from 5% to ~55% SOC. This would seem to indicate that the Bolt EV can handle even higher charge currents in the 5% to 40% SOC range.
 

·
Registered
Joined
·
43 Posts
I did a 30 minute charge at an EVGo 125A/50 kW station and went from 21% SOC to 60%. Station delivered 22 kW in that 30 minutes. 76 miles of estimated range was added:

IMG_2814.jpg IMG_2817.jpg IMG_2818.jpg IMG_2797.jpg
 

·
Registered
Joined
·
2,038 Posts
Thanks, Nero! So I need to remember P = V * A.
I think I have read that a time or two on various sites but it never seems to stay in memory. And 344 volt limit explains why the Bolt isn't charging at or closer to the rated 50 kW on a 125 amp charger.
Thanks again!
 

·
Registered
Joined
·
6,464 Posts
Discussion Starter #16

·
Registered
Joined
·
43 Posts
Hmm...that seems odd. For a 39% increase, I'd expect to see more than 22 kWh. 22 kWh isn't 39% of the known net battery capacity (60 kWh) or of the estimated gross battery capacity (~64 kWh).
It's unclear if the SOC % reported by the station is the raw or the usable part of the battery. I'm guessing it's the usable portion. I didn't think to check in the myChevrolet app what the reported capacity was before and after charging. If I get a chance to repeat the experiment, I'll also be sure to bring my OBDII reader as well to pull more data.
 

·
Senior Member
Joined
·
1,308 Posts
Thanks, Nero! So I need to remember P = V * A.
I think I have read that a time or two on various sites but it never seems to stay in memory. And 344 volt limit explains why the Bolt isn't charging at or closer to the rated 50 kW on a 125 amp charger.
Thanks again!
There is no 344V limit. Neromanceres said that the "nominal" or median pack voltage is 344V but I'm not sure where that number came from since GM's SAE papers say 350V. That voltage is also the "open circuit" voltage when the battery is resting and unused. The voltage during charging will be somewhat higher as the charger is pushing energy into the pack.

All signs I've seen so far point toward a peak charging rate of 55-60 kW at a peak charging current of around 150A. It shouldn't be too much longer before we find out. The Ampera-e is beginning to arrive in Norway and there is at least one 200A CCS charger there. Public CCS chargers at 200+ amps are scheduled to be available in the US in another 2-3 months.
 

·
Registered
Joined
·
43 Posts
Thanks, Nero! So I need to remember P = V * A.
I think I have read that a time or two on various sites but it never seems to stay in memory. And 344 volt limit explains why the Bolt isn't charging at or closer to the rated 50 kW on a 125 amp charger.
Thanks again!
When the Bolt is fully charged, the pack voltage is at ~400 volts. When it is nearly depleted (10% SOC) it sits around 330 volts. So a nearly depleted pack can start charging at ~41 kW on a 125A charger assuming the pack is fully warmed up. If it isn't fully warmed up, the car may request that that charger throttle back the Amps so it might only deliver 100A which would be 33 kW of power. At 50% SOC, pack voltage is around 360 volts for 45 kW. The highest kW that people have seen is 46, which implies that pack voltage is around 368 volts and tapering is about to begin because the car has reached ~60% SOC.

A crude calculation I've come up with is that for every 1 Volt rise in voltage, SOC goes up by about 1.33 %.
 

·
Registered
Joined
·
6,464 Posts
Discussion Starter #20
It's unclear if the SOC % reported by the station is the raw or the usable part of the battery. I'm guessing it's the usable portion. I didn't think to check in the myChevrolet app what the reported capacity was before and after charging. If I get a chance to repeat the experiment, I'll also be sure to bring my OBDII reader as well to pull more data.
I thought that originally, too. But when I looked closer at the numbers, it appears to be gross battery capacity. I just did another session where the tower reported 44% at start of charge and 72% at end of charge (a 28% percent increase) with 18 kWh charged (28% of a 64 kWh battery).
 
1 - 20 of 20 Posts
Top