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Discussion Starter #1 (Edited)
I have decided just for S's and giggles to do a charge rate comparison from empty to full at 240V 12 amps, 240V 15 amps, 120V 12 amps and 120V 8 amps. In preparation for this, I have to do a full discharge cycle on each test run, and I will try to keep charging conditions as close to the same as possible. If a "full" discharge is NOT between 13.9 and 14.1 kWh I will report it as a deviation.

This first section is calculations based on the cars "self estimate" of how long it will take to charge at the different available charge rates, including an estimate from the MyChevrolet App obtained just after starting the charging session.


At a stop light 1 block from home I took a pic of the charging screen, and it showed that charging at 120V 8 amps would take 20 hours, when I reached home 1 block later it showed that at 120V 12 amps it would take 13 hours, and at 240V it would take 4 hours and 30 min (4.5 hours).
Upon reaching home, I plugged in and let the car start charging on my stock EVSE powered with 240V (240V 12 amps), then I checked the charge time estimate on the MyChevrolet app. The MyChevrolet app said it would take 6 hours.

The following is the cars estimate of charge rate into the battery, and the theoretical draw from the grid at each different charge rate, and the calculated efficiency based on those (no doubt) not so accurate estimates. Also, the charging efficiency calculation is based on the AVERAGE draw from the grid over the entire charge cycle, we know that the charge rate slows down significantly on L2 charging when you get close to 100% So the actual charger efficiency is better than the calculated efficiency based on average draw.

14 kWh / 20 = 700 watts charging rate. Theoretical 8 amp draw from the grid is 960 watts
72.9% efficient, pretty pathetic!

14 kWh / 13 = 1,077 watts charging rate. Theoretical 12 amp 120V draw from the grid is 1,440 watts.
74.8% efficient, a bit better but still pathetic.

14 kWh / 4.5 = 3,111 watts charging rate. Theoretical 15 amps 240V draw from the grid is 3,600 watts.
86.4% efficient, better than the 120V charging... but not as good as claims I have seen here.

14 kWh / 6 = 2,333 watts charging rate. Theoretical 12 amps 240V draw from the grid is 2,880 watts.
81% efficient based on the MyChevrolet app estimate.

Now, in the real world my charging took 5.5 hours.
14 kWh / 5.5 = 2,545 watts charging rate. Theoretical 12 amps 240V draw from the grid is 2,880 watts.
88.4% efficient in the real world on the stock EVSE running at 240V.

Keep in mind I have not yet dug out my volt meter and verified my line voltages. If my line voltage is less than 240V (quite possible) then my efficiency is better.

I will be checking my line voltage on each setup and re-calculating if needed.

I will be doing real world charging test on my ClipperCreek LCS-20P as well, and possibly if I don’t need to go anywhere real quick I will do the 120V 12 amp test…. Not sure if I can make myself do an 8 amp charge test, I am OK with wasting time for “science”, but over 20 hours is a heck of a commitment!

Later,

Keith

PS: Yes I get bored easily :)
 

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You need to get something that scans the OBDII port and gives a more accurate value for your Volts and Amps. I use Torque Pro and a Bluetooth OBDII scanner.
 

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Yup, you're crazy. One thing you will find is that charging will be temperature dependent. If it's blasted hot, your AC will kick in sapping some of the electricity that could be used for charging. I've got to imagine that as it gets hot (or as it is really cold) the charger and battery management computers will adjust accordingly. Charge rate will also be dependent on where the guessometer is (full or empty or somewhere in the middle). So you might need to setup a personal weather station where you charge to see what correlations you can find. Too bad you live nowhere near me or you could look for kilmonti6 in weather underground and use my weather station.
 

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Once I move into my new house at end of this month I will charge the car using four settings:
120V 8A, 120V 12A, 240V 12A and 240V 16A. And I will log it all with a digital power analyzer recording both voltage and current. I will also log the ambient temperature conditions. I will try to run the tests under circumstances such that the TMS doesn't need to run.
 

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Discussion Starter #5
You need to get something that scans the OBDII port and gives a more accurate value for your Volts and Amps. I use Torque Pro and a Bluetooth OBDII scanner.
I had a bad experience with a bluetooth OBDII scanner that didn't work well with my old 2011 Volt... it actually left me disabled beside the road and eventually with OnStar support and suggestions I was able to do a "hard reset" to re-enable the propulsion system. Do you have a specific OBDII dongle you can recommend?

Also, wouldn't having the computers "awake" to be able to data log them actually put a parasitic load on the system while you are charging it and thus slow down your charging rate?

Yup, you're crazy. One thing you will find is that charging will be temperature dependent. If it's blasted hot, your AC will kick in sapping some of the electricity that could be used for charging. I've got to imagine that as it gets hot (or as it is really cold) the charger and battery management computers will adjust accordingly. Charge rate will also be dependent on where the guessometer is (full or empty or somewhere in the middle). So you might need to setup a personal weather station where you charge to see what correlations you can find. Too bad you live nowhere near me or you could look for kilmonti6 in weather underground and use my weather station.
I specified a full charge from empty to 100% so guessometer reading is not applicable to my testing. Charging on 240V 12 amp was done at 80F ambient conditions, and my testing today will give me the same 80F ambient conditions for the charging... the 120V 12 amp charge will last 13 hours so temperature will vary, and the 8 amp charge (if I do it) will have even more temperature variation. I do see that the calculated efficiency will be thrown off by the charge rate slowing down as the battery approaches full charge, I will clarify this in the assumed / calculated efficiency in my original post.

Once I move into my new house at end of this month I will charge the car using four settings:
120V 8A, 120V 12A, 240V 12A and 240V 16A. And I will log it all with a digital power analyzer recording both voltage and current. I will also log the ambient temperature conditions. I will try to run the tests under circumstances such that the TMS doesn't need to run.
Glad to know I am not the only crazy one :) Your analysis will be much more detailed than mine... I just got tired of seeing the wild variations in reporting here.

For example, you said 16 amp testing, I said 15 amp... which one is correct? I know that the stated L2 charge rate from Chevy for the 2nd generation Volt is 3.6KW... that implies 240V 15 amps. My LCS 20 is capable of supplying 16 amps, so will the Volt accept 16 amps or 15? Your testing will show better than mine, and I eagerly await the results :)

Later,

Keith
 

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For example, you said 16 amp testing, I said 15 amp... which one is correct? I know that the stated L2 charge rate from Chevy for the 2nd generation Volt is 3.6KW... that implies 240V 15 amps. My LCS 20 is capable of supplying 16 amps, so will the Volt accept 16 amps or 15? Your testing will show better than mine, and I eagerly await the results :)
It is 15A.
 

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Discussion Starter #7 (Edited)
I have verified that my 240V supply is right at 240V, so no re-calculations needed. I just plugged in for my 2nd test with the LCS-20 L2 charger that can supply everything the car is willing to take. The car said it would take 4.5 hours to charge, the OnStar app says it will take 4.75 hours... we will know around 20:30 tonight :)

Keith

PS: Just filled up for the first time since October 5th of last year.. I was down to around half a gallon and I am running the battery flat empty each test burning gas for a couple miles... getting a little to low for comfort!
 

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I have decided just for S's and giggles to do a charge rate comparison from empty to full at 240V 12 amps, 240V 15 amps, 120V 12 amps and 120V 8 amps. In preparation for this, I have to do a full discharge cycle on each test run, and I will try to keep charging conditions as close to the same as possible. If a "full" discharge is NOT between 13.9 and 14.1 kWh I will report it as a deviation.

This first section is calculations based on the cars "self estimate" of how long it will take to charge at the different available charge rates, including an estimate from the MyChevrolet App obtained just after starting the charging session.


At a stop light 1 block from home I took a pic of the charging screen, and it showed that charging at 120V 8 amps would take 20 hours, when I reached home 1 block later it showed that at 120V 12 amps it would take 13 hours, and at 240V it would take 4 hours and 30 min (4.5 hours).
Upon reaching home, I plugged in and let the car start charging on my stock EVSE powered with 240V (240V 12 amps), then I checked the charge time estimate on the MyChevrolet app. The MyChevrolet app said it would take 6 hours.

The following is the cars estimate of charge rate into the battery, and the theoretical draw from the grid at each different charge rate, and the calculated efficiency based on those (no doubt) not so accurate estimates. Also, the charging efficiency calculation is based on the AVERAGE draw from the grid over the entire charge cycle, we know that the charge rate slows down significantly on L2 charging when you get close to 100% So the actual charger efficiency is better than the calculated efficiency based on average draw.

14 kWh / 20 = 700 watts charging rate. Theoretical 8 amp draw from the grid is 960 watts
72.9% efficient, pretty pathetic!

14 kWh / 13 = 1,077 watts charging rate. Theoretical 12 amp 120V draw from the grid is 1,440 watts.
74.8% efficient, a bit better but still pathetic.

14 kWh / 4.5 = 3,111 watts charging rate. Theoretical 15 amps 240V draw from the grid is 3,600 watts.
86.4% efficient, better than the 120V charging... but not as good as claims I have seen here.

14 kWh / 6 = 2,333 watts charging rate. Theoretical 12 amps 240V draw from the grid is 2,880 watts.
81% efficient based on the MyChevrolet app estimate.

Now, in the real world my charging took 5.5 hours.
14 kWh / 5.5 = 2,545 watts charging rate. Theoretical 12 amps 240V draw from the grid is 2,880 watts.
88.4% efficient in the real world on the stock EVSE running at 240V.

Keep in mind I have not yet dug out my volt meter and verified my line voltages. If my line voltage is less than 240V (quite possible) then my efficiency is better.

I will be checking my line voltage on each setup and re-calculating if needed.

I will be doing real world charging test on my ClipperCreek LCS-20P as well, and possibly if I don’t need to go anywhere real quick I will do the 120V 12 amp test…. Not sure if I can make myself do an 8 amp charge test, I am OK with wasting time for “science”, but over 20 hours is a heck of a commitment!

Later,

Keith

PS: Yes I get bored easily :)
Want to see kw in = kw out at over 90% efficiency even on 110vac?

Stop the charge about 1-1.5 hours early, just make sure is around 60f
 

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I had a bad experience with a bluetooth OBDII scanner that didn't work well with my old 2011 Volt... it actually left me disabled beside the road and eventually with OnStar support and suggestions I was able to do a "hard reset" to re-enable the propulsion system. Do you have a specific OBDII dongle you can recommend?
My hypothesis is it's not the dongle that matters, it's how you use it. People who had issues likely had too high a polling rate and were flooding the system until it started to crash. Low and slow. Especially when charging - you don't need data points every 100ms. 1000ms is plenty granular. Also don't be polling more PIDs than you need to. Just the minimum.

Also, wouldn't having the computers "awake" to be able to data log them actually put a parasitic load on the system while you are charging it and thus slow down your charging rate?
The volt computer is always on during charging - this is part of the reason why 240V is more than just 2x faster as you'd expect if you kept the amps the same and doubled voltage. The computer, BMS/TMS are fixed overheads that are on whether you charge for 4h or 12h.

If you are polling OBD and the computer goes to sleep - you'll lose data. Torque/OBD does not force the computer to wake up. The PIDs will just freeze (no data).
You can test this when the car is not charging - start polling some PIDs, then get out and lock the door. You'll likely lose connection as the computer went to stage 1 sleep. Unlock the door and it starts up again.
When charging, you can continuously get the charging details, even when the car door is locked.
 

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Discussion Starter #10 (Edited)
I did an Onstar check of status each hour of the charge with the following results:

At 16:05 Battery fully depleted, started charging.

At 17:05 battery level 24%, 14 miles range. Gain of 24% and 14 miles.

At 18:05 battery level 47%, 27 miles range. Gain of 23% and 13 miles.

At 19:05 battery level 69%, 40 miles range. Gain of 22% and 13 miles.

At 20:05 battery level 91%, 53 miles range. Gain of 22% and 13 miles.

At 20:35 battery level 100%, 58 miles range. Gain of 9% and 5 miles. Says still charging.

20:39 OnStar text saying charging complete, 100% and 58 miles.

I would call that a solid 4.5 hour charge. Ambient temperature was the same as yesterdays charge at 80F.

Average gain of 22.75% capacity per hour for the first 4 hours, and 9% in the last half hour, so using the EPA rated range that would be a gain of 12 miles of range per hour of charging for the first 4 hours, and 5 miles of range gained in the last half hour of charging.

Later,

Keith
 

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I think you have invented a new kind of efficiency. Usually talk on this site refers to 15 kWh from the grid to give 14 kWh in the battery. The lost 1 kWh is used by the car in charging for battery conditioning and heat loss by the on board charger. Your efficiency is based on time estimates from the car which I have found to be over estimates. On my 2013 and 2015 the full charge estimate was 4 hours and I would get a consistent 3.75 hours. The 2013 would use more power even though it had less usable charge. So not all Volts take the same amount of power.
 

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How long does it take to charge from empty at 12amps; 120volts? I've always been using 240v, which averages around 4 hours 15-25min for me. I would guess that 120v/12amps would be a bit under 11 hours, but GM says 13 hours. Just curious.
 

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Discussion Starter #13
How long does it take to charge from empty at 12amps; 120volts? I've always been using 240v, which averages around 4 hours 15-25min for me. I would guess that 120v/12amps would be a bit under 11 hours, but GM says 13 hours. Just curious.
That curiosity is why I am doing this test :) Right now I am doing an empty to full on 120V 8 amps. I will try to do an empty to full cycle on 120V 12 amps during my work days over the weekend.

Keith
 

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Discussion Starter #14 (Edited)
Girlfriend decided 2 hours into charging that she wanted to go to Walmart, so had to re-start the 8 amp charge test after that...

Charging conditions were clear weather and started charging with ambient temperature in the high 70's, dipped into the high 50's over night, and back into the low 80's for end of charge.

Battery fully depleted, started charging at 20:35 at 8 amps Predicted charge complete 16:15 PM (20.5 hours) If I can average 6% per hour that would mean 16 hours 40 min. So finish around 13:00.

At 21:35 battery level 1%, 4 miles range. Gain of 1% and 4 miles. MyChevrolet app does not read % charge well at the low end.

At 22:35 battery level 12%, 7 miles range. Gain of 11% and 3 miles. Actual gain was 6% per hour over two hours.

At 23:35 battery level 18%, 10 miles range. Gain of 6% and 3 miles.

At 00:35 battery level 24%, 14 miles range. Gain of 6% and 4 miles.

Sleep time, I am not killing myself or annoying the girlfriend by waking up every hour to take readings :)

At 06:35 battery level 59%, 34 miles range. Gain of 35% and 20 miles. Ave 5.83% and 3.33 miles/hour

At 07:35 battery level 65%, 38 miles range. Gain of 6% and 4 miles.

At 08:35 battery level 71%, 40 miles range. Gain of 6% and 2 miles.

At 09:35 battery level 76%, 43 miles range. Gain of 5% and 3 miles.

At 10:35 battery level 82%, 47 miles range. Gain of 6% and 4 miles.

At 11:35 battery level 87%, 50 miles range. Gain of 5% and 3 miles.

At 12:35 battery level 92%, 53 miles range. Gain of 5% and 3 miles.

Started taking reading every half hour here.

At 13:05 battery level 95%, 55 miles range. Gain of 3% and 2 miles.

At 13:35 battery level 98%, 56 miles range. Gain of 3% and 1 miles.

At 14:05 battery level 100%, 57 miles range. Gain of 2% and 1 miles.

At 15:05 battery level 100%, 58 miles range. Gain of 0% and 1 miles.

So, a total of 17.5 hours to reach 100% and another hour to balance the battery cells and in the process gain 1 more mile on the guess-o-meter. Average charge rate was 5.7% per hour to get to 100% or 5.4% per hour to reach charge complete. Using the EPA rated range that means you gain 3.0 miles of range per hour of charging up until the last hour where you probably gain zero to 1 mile of range.

Keith
 
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