Collecting data:Off-the-wall power for turtle to 100% charge

[RegGuheert]

How about adding a column that shows percentage of a new Leaf (new Leaf from the NREL study = 25.414 kwh from the wall)?

That would be interesting. But one thing I've been thinking we need to make all this data more useful is the ambient temperature during the recharge. Comparing charging energy at 30F against a reference which was likely measured around 70F is more useful if the temperature differences are known.

P.S. TickTock: Thanks for adding my last datapoint! I edited my post to include my odometer reading, also. Please add that in when you have a chance. TIA!

 

[LEAFer]

Not very happy at the moment :evil: See below. Will attempt to borrow a local Gid Meter next week.

My son took 6 "trips" (CarWings definition) on Friday (exactly 21 months, 27k miles) after a 100% full charge. I should have set to subsequent 100% charge on Saturday, but timer was set for 80%.

 

[TonyWilliams]

I suggest that we use the NREL LEAF Teardown and Detailed Test Results as the best values available to calculate recharge energy efficiency:

Energy from the wall from dead to 100%: 25.414 kWh
Energy from the onboard charger to battery: 22.031 kWh
Energy from the battery during discharge: 21.381 kWh

I will assume these tests were done using an L2 charger at 16A. From these numbers, we get the following energy efficiencies:

- L2 charging energy efficiency, wall to usable, unknown driving conditions, Dead(?) to 100%: 84.1%
- L2 charging energy efficiency, wall into battery, Dead(?) to 100%: 86.7%
- Battery energy efficiency, 100% to Dead(?), unknown driving conditions: 97%

The 84.1% number is the efficiency which is most pertinent for this thread, since we are trying to estimate usable energy available from a 100% recharge.

At what voltage will you assume? 200v, 208v, 240v ? We know most houses in the USA have 240v, but in the wild, 208v is quite common.

Obviously, an efficiency factor variable.

 

[RegGuheert]

At what voltage will you assume? 200v, 208v, 240v ? We know most houses in the USA have 240v, but in the wild, 208v is quite common.

Obviously, an efficiency factor variable.

Good point! While most of us are charging at 240VAC (230VAC to 250VAC), it is entirely possible that NREL tested at 208VAC.

OTOH, please note that during L2 charging the LEAF apparently adjusts the current from the wall to maintain 3300W into the battery. So the ratio of charging power to overhead power for pumps, etc., should be constant. (Although I do not know if the LEAF will draw the ~18A from the EVSE required to maintain 3300W into the battery from 208VAC.) I doubt that the electrical efficiency of the charger itself varies much between 208VAC and 250VAC. It's probably around 97% or so in that range. Does anyone have measurements?

 

[camasleaf]

Just finished charging turtle to 100% on my new Leaf now at 430 miles. The Blink reported 24.9 kWh in 6.44 hours. I will try to turtle the older Leaf tomorrow.

The older Leaf finished charging from turtle to 100%: 23.2 kWh in 6:14 hours. So after almost 23000 miles in 16 months the capacity dropped about 1.5 kWh or 7% (assumed 90% efficiency).

 

[Stoaty]

The older Leaf finished charging from turtle to 100%: 23.2 kWh in 6:14 hours. So after almost 23000 miles in 16 months the capacity dropped about 1.5 kWh or 7% (assumed 90% efficiency).

Battery aging model predicts 8.8% capacity loss for your location, assuming 4 miles/kwh and not parked in the sun. Pretty close. For Phoenix, AZ the model predicts 15.3% capacity loss for the same distance driven and time of ownership. It all depends on the climate.

 

[surfingslovak]

Battery aging model predicts 8.8% capacity loss for your location, assuming 4 miles/kwh and not parked in the sun. Pretty close. For Phoenix, AZ the model predicts 15.3% capacity loss for the same distance driven and time of ownership. It all depends on the climate.

Stoaty, the model seems to be working amazingly well. Kudos to you for investing all this time and effort, it really shows. Unfortunately, I will have to download OpenOffice, since some of the formulas and formatting are no longer compatible with Excel.

That said, here are my last three full charges measured on a ChargePoint station. It was at night, and the ambient temps were pretty high for the Bay Area (~ 70 and 80 F). The results seem to correlate well with an empirically determined range loss of 10% at 14 months and 15,600 miles.

Note : The car was connected longer than it actually took to complete the charge.


As a side note, the car accepted 24.34 kWh from the wall when it was seven months old. I did not perform this test when the vehicle was new. Now I wish I did, it would be great to have it as baseline.

 

[Stoaty]

That said, here are my last three full charges measured on a ChargePoint station. It was at night, and the ambient temps were pretty high for the Bay Area (~ 70 and 80 F). The results seem to correlate well with an empirically determined range loss of 10% at 14 months and 15,600 miles.

Note : The car was connected longer than it actually took to complete the charge.

If I calculate your capacity as 22.5 kwh from wall/25.4 kwh from wall for new Leaf, I get 88.6% capacity, or loss of 11.4%. The model predicts 8.68% range loss at 14 months and 15,600 miles for Santa Clara, assuming 4 miles/kwh driving efficiency and not parking in the sun. If you parked in the sun much or drove less efficiently, the predicted loss would be a bit more. Both numbers are within spitting distance of the 10% range loss you determined empirically.

 

[surfingslovak]

If I calculate your capacity as 22.5 kwh from wall/25.4 kwh from wall for new Leaf, I get 88.6% capacity, or loss of 11.4%. The model predicts 8.68% range loss at 14 months and 15,600 miles for Santa Clara, assuming 4 miles/kwh driving efficiency and not parking in the sun. If you parked in the sun much or drove less efficiently, the predicted loss would be a bit more. Both numbers are within spitting distance of the 10% range loss you determined empirically.

Yes, it's close enough. I only have range data available starting from December 2011, when the car was about six months old. I'm fairly confident about the 10% range loss figure relative to that performance. Note that this implies 21 kWh usable in early December 2011, as measured in my first 100-mile run. The car was still showing 281 Gids in April 2012, although it was exhibiting about 5% range loss at the time.

My long-term energy economy is about 4.5 m/kWh. I can't be really sure, because CarWings remained inaccurate until the very end, and I reset my onboard gauges frequently. The car was parked outside at home, usually in partial shade. Covered parking at work. South Bay is much warmer than San Francisco, but I tried to avoid six temperature bars. This was difficult to do on hot summer days, but I usually wouldn't hit that until noon, or not at all, if I parked the car in the parking garage at work all day.

I had between 15 to 20 turtle events due to the work I did on the reverse SOC table, and other tests. I followed Tony's lead in this case, and this could have caused slightly larger than anticipated capacity loss. Would extra 1-2% loss would be fair? I babied the battery otherwise, and maintained a low state of charge when I didn't need to go anywhere.

 

[Stoaty]

Yes, it's close enough. I only have range data available starting from November 2011, when the car was about five months old. I'm fairly confident about the 10% range loss figure relative to that performance. Note that this implies 21 kWh usable in early November 2011, as measured in my first 100-mile run. The car was still showing 281 Gids in April 2012, although it was exhibiting about 5% range loss at the time.

My long-term energy economy is about 4.5 m/kWh. I can't be really sure, because CarWings remained inaccurate until the very end, and I reset my onboard gauges frequently. The car was parked outside at home, usually in partial shade. Covered parking at work. South Bay is much warmer than San Francisco, but I tried to avoid six temperature bars. This was difficult to do on hot summer days, but I usually wouldn't hit that until noon, or not at all, if I parked the car in the parking garage at work all day.

I had between 15 to 20 turtle events due to the work I did on the reverse SOC table, and other tests. I followed Tony's lead in this case, and this could have caused slightly larger than anticipated capacity loss. Would extra 1-2% loss would be fair? I babied the battery otherwise, and maintained a low state of charge when I didn't need to go anywhere.

The 4.5 miles/kwh decreased your predicted capacity loss, but I figured 2 days/week times 0.5 (for partial shade) = 1 day worth of sun exposure, and ended up with 8.70% predicted capacity loss. Unfortunately, I do not have any way to estimate how much negative effect turtle events might have on battery capacity.

 

[surfingslovak]

The 4.5 miles/kwh decreased your predicted capacity loss, but I figured 2 days/week times 0.5 (for partial shade) = 1 day worth of sun exposure, and ended up with 8.70% predicted capacity loss. Unfortunately, I do not have any way to estimate how much negative effect turtle events might have on battery capacity.

I know that grommet is reporting a similar loss of range after 16 months and 11,000 miles. He lives in the same microclimate, and seems to park his car out in the sun more often than I did. Grommet does not have a Gid meter, and he would be a good candidate to measure wall energy needed to charge his Leaf from turtle to full.

 

[ColumbiaRiverGorge]

Turtle to 100% today at 24,000 miles (East of Portland, OR). My EVSE upgrade revision 2 was used (L2). My meter indicated 21.66 k/Wh total. I began charging at 46 degrees and ended at 53 degrees. This took 5 hours and 56 minutes. This was my first turtle event and it was manufactured in May of 2011. It has spent two summers in The Dalles, OR, while at work (45 hours a week). I park it in the sun usually, on gravel, right next to a beige shop. Some days it reaches above 100 degrees there. I live at 800 feet above Hood River, near the North side of Mt. Hood. It is much cooler up here, as it has been freezing some nights, and has been much cooler since the beginning of October. My lifetime average, per Carwings, is 4.2 m/Kwh. What do you think my battery degradation is at? I wish I would have done an initial test when I took delivery on 07/06/11, but there were so many other cool things I was learning about the car. This car is garaged whenever it is home and the garage gets cold in the winter.

 

[Stoaty]

I know that grommet is reporting a similar loss of range after 16 months and 11,000 miles. He lives in the same microclimate, and seems to park his car out in the sun more often than I did. Grommet does not have a Gid meter, and he would be a good candidate to measure wall energy needed to charge his Leaf from turtle to full.

Assuming 4 miles/kwh and 4 days a week in the sun, the model predicts a 9.38% capacity loss for Grommet. Next weekend I will be working a lot more on validation of the model, especially looking at outliers to see if there is anything I can learn from them.

 

[camasleaf]

The older Leaf finished charging from turtle to 100%: 23.2 kWh in 6:14 hours. So after almost 23000 miles in 16 months the capacity dropped about 1.5 kWh or 7% (assumed 90% efficiency).

Battery aging model predicts 8.8% capacity loss for your location, assuming 4 miles/kwh and not parked in the sun. Pretty close. For Phoenix, AZ the model predicts 15.3% capacity loss for the same distance driven and time of ownership. It all depends on the climate.

Lifetime average at 4.4 miles per kWh. Rarely parked in the sun, maybe 4-5 days all this summer. So yes, the aging model seems accurate.

 

[Stoaty]

Lifetime average at 4.4 miles per kWh. Rarely parked in the sun, maybe 4-5 days all this summer. So yes, the aging model seems accurate.

The model predicts end of life (70%) for your Leaf at 10.3 years and 175,000 miles assuming you continue to drive the same amount annually. I guess we will have to wait another 9 years to see if it is correct.

 

[DaveEV]

OTOH, please note that during L2 charging the LEAF apparently adjusts the current from the wall to maintain 3300W into the battery. So the ratio of charging power to overhead power for pumps, etc., should be constant. (Although I do not know if the LEAF will draw the ~18A from the EVSE required to maintain 3300W into the battery from 208VAC.) I doubt that the electrical efficiency of the charger itself varies much between 208VAC and 250VAC. It's probably around 97% or so in that range. Does anyone have measurements?

IIRC, Phil measured charging on L2 somewhere around 10-20W when charging. He's posted it somewhere. Or well under 1% when charging. If it dissipated any more heat than that the thing would melt.

All the EVSE has to do is keep the contactor closed when charging.

 

[RegGuheert]

IIRC, Phil measured charging on L2 somewhere around 10-20W when charging. He's posted it somewhere. Or well under 1% when charging. If it dissipated any more heat than that the thing would melt.

All the EVSE has to do is keep the contactor closed when charging.

I was referring to the liquid-cooled charger in the back, not the EVSE. Also, I am excluding the pumps, etc., in my 97% estimate. That efficiency number may move around a percent or so between 208VAC and 240VAC, but probably not much more than that.

 

[surfingslovak]

IIRC, Phil measured charging on L2 somewhere around 10-20W when charging. He's posted it somewhere. Or well under 1% when charging. If it dissipated any more heat than that the thing would melt.

Were you referring to this post or perhaps something else? Note that Phil measured energy delivered to the battery, and this presumably does not include any energy lost in the pack itself during charge and discharge.

Here are my charging measurements on the Leaf:

Charging using the original 120v EVSE: (112.5v recorded at EVSE input)

Standby Power: 4.9w
Charge Power in: 1.451kW
Power to Leaf Battery: 1.125kW
Total Power Lost: 326w
Total Charge Efficiency: 77.5%

These measurements are all using our Rev2 Upgraded EVSE:

120v: (112.6v recorded at EVSE input)
Standby Power: 1.7w
Charge Power in: 1.436kW
Power to Leaf Battery: 1.125kW
Total Power Lost: 311w
Total Charge Efficiency: 78.3%

240v: (239.8v recorded at EVSE input)
Standby Power: 3.4w
Charge Power in: 3.756kW
Power to Leaf Battery: 3.414kW
Total Power Lost: 342w
Total Charge Efficiency: 90.9%

Click to open

 

[camasleaf]

Turtle to 100% today at 24,000 miles (East of Portland, OR). My EVSE upgrade revision 2 was used (L2). My meter indicated 21.66 k/Wh total. .... What do you think my battery degradation is at? ....

My new Leaf at 430 miles charged 24.9 kWh in 6.44 hours. But the battery was likely warmer compared to yours by at least 10 degrees. The capacity will be less about 1% per 4F so about 2-3% compared to mine. So at the same temp you would have charged 22.2 kWh. That means you lost around 10%, about 3% more than my old Leaf now at 23000 miles but did not stay in the sun.

 

[surfingslovak]

My new Leaf at 430 miles charged 24.9 kWh in 6.44 hours. But the battery was likely warmer compared to yours by at least 10 degrees.

Way to go! Measuring two cars, new and old, in the same environment is awesome. This gives us a good and direct comparison. Would you know what the date of manufacture was for both Leafs? (It's on a sticker on the driver door pillar.)