A
Anonymous
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sgt1372 said:
sgt1372 said:
So, why are you buying ANY of that stuff???
Chargepoint and EVGo chargers
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So, why are you buying ANY of that stuff???
The sweet spot for HIGHEST charge rate is not a low SOC.
The fastest charge rate I have seen is in the 45% to 50% SOC. Which makes perfect sense.
Volts x Amps = watts.
At Low SOC your volts are low, so while the charger is maxed out at 125 amps, you get only ~ 32 kW of input.
At High SOC your volts are getting higher and higher so the amps throttle down. So you get lower kW charging once again.
On a 50 kw charger you will always get the most power and most miles per 30 minutes by starting with about 40% in the battery.
If you have one of those 24 kW chargers, it really doesn't matter when you start charging under 85% of course.
The fastest charge rate I have seen is in the 45% to 50% SOC. Which makes perfect sense.
Volts x Amps = watts.
At Low SOC your volts are low, so while the charger is maxed out at 125 amps, you get only ~ 32 kW of input.
At High SOC your volts are getting higher and higher so the amps throttle down. So you get lower kW charging once again.
On a 50 kw charger you will always get the most power and most miles per 30 minutes by starting with about 40% in the battery.
If you have one of those 24 kW chargers, it really doesn't matter when you start charging under 85% of course.
GetOffYourGas said:
GetOffYourGas
Well-known member
Yes, but it's a question of how quickly do those amp ramp down when you become voltage-limited. From plots posted here and elsewhere, it seems there is a huge drop in power at about 50-55% SoC on the Bolt. So I don't know your assertion is correct.
I don't have a car to test (and even if I did, there are no DCQC convenient to me). But you are making a statement contrary to real data posted elsewhere.
I don't have a car to test (and even if I did, there are no DCQC convenient to me). But you are making a statement contrary to real data posted elsewhere.
SeanNelson
Well-known member
I'll be very interested to see what the Bolt is capable of when we start to get some 200A DC fast chargers out there.gpsman said:
oilerlord
Well-known member
SeanNelson said:
FWIW:
"On DC fast charging, the Bolt EV can recharge at 80 kW, which Chevy says is enough to recover 90 miles of range in 30 minutes."
http://www.greencarreports.com/news/1107830_chevy-bolt-ev-will-offer-aerovironment-charging-station
GetOffYourGas
Well-known member
oilerlord said:
If we assume that the battery is nominally 400V, then 80kW turns out to be ...drum roll... 200A.
I agree with Sean. I'm very interested to see what the charging profile looks like on a 200A charger. I would assume that the Constant-Voltage region (above about 50%) is the same, but what about the first 50%? I could probably take an educated guess. But then I wouldn't have guessed that the car tapers the way it does above 50%.
GetOffYourGas said:
No I am not posting anything hypothetical or contrary. I own a Bolt with nearly 2000 miles on it.
My real world, several charging event history is very consistent.
I have never taken my battery lower than about 30%.
Here are the REAL LIFE charging rates on a 125 amp charger.
30% to 45% slow ramp from 28 kw to 46 kw.
45% to 66% = bounces between 37 kw and 46 kw.
(Maybe based on battery temperature, maybe due to the supply line to the charger, I don't know, high but random output in this range.... average of 42 kw.)
66% to 86% = 24 kw
86% to 93% = 16 kw
93% to ??? = 10 kw
It's interesting I observe a gentle ramp on the low side and deliberate sudden steps down on the high side. But that shows the CHARGER is maxed out on amps on the lower side, and the car is sending commands to the DCFC to slow down on the high side.
Here's a photo of my car charging at 24 kw with a nearly full battery. This can hardly be called "slow".
It seems, for all practical purposes, this car charges on about a bell shaped curve: kw vs. % charge.
I'm not seeing a big advantage charging from a low state of charge. It is coincidence... nature of the beast that you normally arrive at a DCFC with low SOC.
All things being equal:
You could start low charge and be slow, and speed up during your 30/60 minute charging sessions.
You could start at mid-charge and start charging fast, and slow down during the course of your 30/60 minute charging sessions.
You are going to get the same number of miles either way. Fact. Not Fiction.
The only thing I think is worthwhile is don't go below 15% or above 86% when charging is slower, but still 10 kw. Faster than nearly all L2 chargers.
It seems, for all practical purposes, this car charges on about a bell shaped curve: kw vs. % charge.
I'm not seeing a big advantage charging from a low state of charge. It is coincidence... nature of the beast that you normally arrive at a DCFC with low SOC.
All things being equal:
You could start low charge and be slow, and speed up during your 30/60 minute charging sessions.
You could start at mid-charge and start charging fast, and slow down during the course of your 30/60 minute charging sessions.
You are going to get the same number of miles either way. Fact. Not Fiction.
The only thing I think is worthwhile is don't go below 15% or above 86% when charging is slower, but still 10 kw. Faster than nearly all L2 chargers.
Fiction.gpsman said:
Normally batteries can accept higher rates of charge at lower states of charge.
This can be artificially limited by today's 125A current limit on CHAdeMO. CCS has theoretically allowed up to 200A but essentially all real-world CCS chargers were also designed with the 125A limit because there weren't any cars on the road that needed more.
The charging voltage increases as the battery fills so if a Bolt EV hits the top current limit it will end up charging slightly faster as the battery fills simply due to the ramping of the charging voltage.
Battery charging rates are also strongly influenced by the cell temperatures. Although Lithium cells can discharge at relatively high rates when cold they cannot be charged quickly when cold. This is almost certainly why you were seeing a charge rate that started at 28 kW which then slowly increased to 42 kW (as you mentioned in a prior posting). It wasn't due to the state of charge, it was due to the battery pack temperature.
Actually, the Bolt EV can begin charging at 125A
from a very low state of charge. Here is a picture of it charging at about 125A and near 42 kW at around 6% state of charge:
https://youtu.be/5zI8qO3_g3w
The advantage of starting with a low state of charge is that you can maintain a 42-46 kW charging rate at 125A for a longer period of time until the current is reduced to around 100A when the battery reaches around 53% state of charge and thus drops to about 37 kW. Later, at about 68%, it drops down to 24 kW where you were charging in the image you posted. With 209 estimated miles showing in that image your battery was likely just under 85% full and was moments away from dropping down to a 15 kW rate.
I do agree with your recommendation to avoid routinely charging at much less than 15% state of charge but not for the reason you state (slow charging, which isn't actually true). A better reason would be avoiding stress on the battery and ensuring that you have some backup Reserve range in case the charger is not available for some reason or your planned driving range is unexpectedly reduced due to bad weather or detours. I generally aim to arrive with 15-20%.
In summary, it does actually make sense to ideally schedule your road trip charging stops so that your battery is relatively empty in order to maximize the time spent charging above 40 kW.
GetOffYourGas
Well-known member
Thanks for the info, Jeff. This is more in-line with other things I have read.
Also, keep in mind that if you are on the road, and just depleted the battery from 100% to say 20%, it will have been warmed up due to use (and TMS), so it will presumable charge faster at the low end.
I have to laugh, though, at the whole premise of this discussion. It assumes that there is a charger available when and where you need it. For me, there are only 2-3 DCQC along the routes that I would take a Bolt anyway. You better believe that I would be stopping at all of them for that "just in case" charge. Maybe in 5 years from now things will have changed. Or maybe still not significantly enough to be able to optimize my travel plans around what SoC I should charge at.
Also, keep in mind that if you are on the road, and just depleted the battery from 100% to say 20%, it will have been warmed up due to use (and TMS), so it will presumable charge faster at the low end.
I have to laugh, though, at the whole premise of this discussion. It assumes that there is a charger available when and where you need it. For me, there are only 2-3 DCQC along the routes that I would take a Bolt anyway. You better believe that I would be stopping at all of them for that "just in case" charge. Maybe in 5 years from now things will have changed. Or maybe still not significantly enough to be able to optimize my travel plans around what SoC I should charge at.
SparkEVPilot
Well-known member
GetOffYourGas said:
Great advice! I drive a Spark EV with the quick charge option and I always have a Plan B and, sometimes a Plan C, so I do not get stranded. I believe we EV drivers will soon experience more and more delays at the DCQC locations as the new cars with larger batteries start getting in line to charge too. More and faster chargers are needed now.
GetOffYourGas said:
Which routes?
VW, through its Electrify America subsidiary, is planning an aggressive rollout of US nationwide 150+ kW DC charging locations with up to 50 locations being added in California by Q2 2019 and maybe 100-150 locations in other states. The full plans stretch out for 10 years so there will almost certainly be more locations added in 2020 and beyond.
In addition, CA is already separately funding several dozen additional highway DC locations to be installed within the same 2 year timeframe.
Here is an article I recently wrote:
http://www.hybridcars.com/vw-reveals-tesla-like-ev-charging-plans/
Here is an interactive google overlay map created by someone else that shows the locations of the CA-funded stations being added from now until late 2019. These locations may initially have only 50 kW but they include a pre-wired location for adding an additional 100+ kW charger and the transformer and grid connection is sized for that.
https://www.google.com/maps/d/u/0/viewer?mid=1VEJLK0-wcAhWV8Q0MirTLULd5mg&ll=34.69568825600552%2C-119.11231046875002&z=7
GetOffYourGas
Well-known member
JeffN said:
I live in Syracuse, NY. Most of my driving is eastward. So the first DCQC I hit is a cluster in Albany, NY. Then I'll either head north towards Burlington, VT (DCQC in Middlebury VT) or south towards NYC (a few DCQC along the thruway - I-87). The single longest stretch is Albany to home, about 150 miles. So on the way home, I'd have to charge to nearly full in order to make it.
I am familiar with VW's settlement in CA. It will be a few years (if at all) before that money finds its way to my neck of the woods. I know I-90 has been identified as a corridor both by VW and by the Governor of NY. Both offer the potential of money towards development. Judging from the speed of our government, I wouldn't be surprised if that's still 5-10 years away.
So the bottom line is, if I lease a Bolt today, I am probably stuck with the current infrastructure for the duration. If I buy and keep for 10 years, things may eventually get better.
Ok. I stand corrected.
After 3 DCFC sessions where my car slowly ramped up to 46 kw then stair stepped down in the manner we are all familier with.....
On my 4th DCFC seasion it started at 42 kw from 10% SOC.
I never considered 55 degrees "cold" ( the coldest my car had ever been) but I guess that is cold enough to cut charging rate by nearly half and force it to do a slow ramp. Who knows. Maybe it was the charger.
Now I see benifit to waiting for a low SOC to charge if your battery is very warm. I read 77 degrees is optimal.
After 3 DCFC sessions where my car slowly ramped up to 46 kw then stair stepped down in the manner we are all familier with.....
On my 4th DCFC seasion it started at 42 kw from 10% SOC.
I never considered 55 degrees "cold" ( the coldest my car had ever been) but I guess that is cold enough to cut charging rate by nearly half and force it to do a slow ramp. Who knows. Maybe it was the charger.
Now I see benifit to waiting for a low SOC to charge if your battery is very warm. I read 77 degrees is optimal.
It's interesting that Chevy considers 4 miles per kWh as the "average" of what this car will do (and I find that is very accurate with heat and AC off) but the Chargepoint App considers the car to get 3.33 miles per kWh when you charge at thier stations and they give you an estimate of miles added.
GetOffYourGas
Well-known member
The Chargepoint App is counting kWh from the EVSE, GM is counting from the battery. In the former case, there are additional losses to charge the battery. 3.33 / 4 = 83.25%. 16.75% loss seems likely/reasonable to me.
No. Not what I am saying.
ChargePoint says 160 miles added.
Car dashboard says 192 miles actually added.
It's the same kWh.
The car can use past history.
The EVSE cant't so they had to pick a number.
I just found it interesting "They" (ChargePoint) picked the number 3.33 for miles per kWh.
They had to pick something, or not provide a number to the customer at all.
ChargePoint says 160 miles added.
Car dashboard says 192 miles actually added.
It's the same kWh.
The car can use past history.
The EVSE cant't so they had to pick a number.
I just found it interesting "They" (ChargePoint) picked the number 3.33 for miles per kWh.
They had to pick something, or not provide a number to the customer at all.
GetOffYourGas said:
GetOffYourGas
Well-known member
Ah, I misunderstood. Thanks for clarifying.
I'm guessing that 3.33 is based on some typical or fleet average value? Does the Chargepoint technically know if it is plugged into a Bolt versus an eGolf, i3, or something else?
I'm guessing that 3.33 is based on some typical or fleet average value? Does the Chargepoint technically know if it is plugged into a Bolt versus an eGolf, i3, or something else?
WetEV
Well-known member
stolenmoment said:
Assuming you have only one electric...
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