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

[edatoakrun]

="camasleaf"...The capacity will be less about 1% per 4F...

Is there any real documentation for that statement, either the amount of loss or consistent over a large temperature range?

I think this "rule of thumb" for battery capacity reduction with temperature may considerably overstate reduced capacity at lower battery temperatures.

It is very difficult to accurately measure battery temperature, and difficult to segregate the loss of capacity in a range test, from lower m/kWh due to colder driving conditions.

Last year (and in many range tests since, in the ~45 F to ~95 F range where I can tolerate driving without heater or AC use) I seem to have found capacity loss more like 1% per 8 F, than "1% per 4F", though my total range loss seems to come pretty close to that "1% per 4F" amount.

IMO, the most accurate way to determine capacity loss at lower ambient/battery temperatures would be for those monitoring recharge capacity to also note temperature as a factor:

https://docs.google.com/spreadsheet/ccc?key=0An7gtcYL2Oy0dG9vbzBiMW8tc1c2UzFKM3RiUG5ORHc#gid=0" onclick="window.open(this.href);return false;

edatoakrun

On 11/8/(11) I attempted to replicate the route and conditions of an earlier trip, which I had kept careful notes of, to try to see what sort of range reduction is caused by reduced m/kWh due to lower temperatures, and what proportion of this reduction is due to reduced battery capacity. I did this on a dry day with windows up, without using the heater or windshield wipers. I believe that I got about 5% reduction in battery capacity, and a slightly larger decrease in driving efficiency (m/kWh) resulting in a total range reduction of over 10%...


...This approximately 40 degree decrease in temp when charging, and 50 degree reduction when driving, resulted in about 10% recorded range reduction...

http://www.mynissanleaf.com/viewtopic.php?f=31&t=6701&start=60" onclick="window.open(this.href);return false;

 

[camasleaf]

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?

Now you have me worried. The 2011 was built on 04/11. The 2012 was build on 04/12. Were was the 2012 for 6 months? The dealer said it was the floor model for a month, that means it was on the air conditioned floor for two months. Two months in route from Japan to Portland. That still leaves 2 months, somewhere in the sun. The initial test of 24.9kWh turtle to 100% was done after two days of overnight 100% on L1, so there should not have been any equalization going on. I guess it is OK.

 

[camasleaf]

="camasleaf"...The capacity will be less about 1% per 4F...

Is there any real documentation for that statement, either the amount of loss or consistent over a large temperature range?

From Tony's chart.

 

[edatoakrun]

="camasleaf"...The capacity will be less about 1% per 4F...

Is there any real documentation for that statement, either the amount of loss or consistent over a large temperature range?

From Tony's chart.

By "real" I meant derived from accurate observations.

The range chart does not differentiate between ambient and battery temperature, so it does not even reflect the different effects of battery capacity variation and driving efficiency variation due to temperature.

 

[LEAFer]

Ran another test. This time Dead-to-100%. Still have all 12 capacity bars.

Last time (Oct 13; posted above on Oct 14) it finally reached Turtle after using heater/AC and re-charge times of 20:00/07:00. 20.722 kWh (including balancing).

This time I drove additional miles to get super-low, reaching turtle on approach to garage. Then I ran heater/AC and occasionally reverse/forwarded the car. Finally the dash showed "Brake" (and the associated symbol) and I could no longer shift into D or R. However, the fan continued to blow and lights were still on (not "totally" dead, I guess) -- I am assuming the fan runs off traction battery, not 12V. At that point I powered off manually.

Also, interestingly, after the "Brake" prompt came up and an unsuccessful attempt to shift to R, putting it back in P showed all power circles back up, *and* the Turtle was *GONE* ! Instead, a red battery symbol appeared. (See photos below.)

Dead to 100%: 21.049 kWh (per ChargePoint account)
Time: 12:25 to 18:15(approx) = 5:50
244-245V, 15.2-15.4amps.
Temp: 63-67F, parked mostly in shade; 5 TBs.

( I don't think there'll be a "balancing act" tonight, but will update this post if there is. )

 

[surfingslovak]

Also, interestingly, after the "Brake" prompt came up and an unsuccessful attempt to shift to R, putting it back in P showed all power circles back up, *and* the Turtle was *GONE* ! Instead, a red battery symbol appeared. (See photos below.)

Fascinating! That's one dead Leaf you had there. The data from your last post would be indicative of a Gid count close to 230. Did you get a reading at the meetup in Sacramento?

Edit: never mind, it was 259 Gids with pack voltage of 393.5V four months ago. Looking back at the performance of my car, it's plausible that you lost lost 10 to 20 Gids over the course of the summer.

 

[LEAFer]

Did you get a reading at the meetup in Sacramento?

Edit: never mind, it was 259 Gids with pack voltage of 393.5V four months ago. Looking back at the performance of my car, it's plausible that your lost lost 10 to 20 Gids over the course of the summer.

No, I had a plan to borrow one earlier this week, but the plan got messed up ...

Yes, I believe the two months of summer heat (still nothing like Phoenix) during Aug & Sep caused the loss. Evenings still always cooled off, and we only hit ~105 a few days. In Sep we hit 90 or higher (but rarely 100; mostly 90-94) at least 24 days out of 30, but again it cooled off at night (70s). (To be more accurate I'd have to look up the weather stats; that's from memory.)

 

[JeremyW]

Today I recharged to 100% from 4 miles into VLBW (did not have time to go to turtle). 22.5 kWh from a commercial chargepoint. Door says made Feb 2012. Gid count in June was 271 at 100% for the second and third charge. Will hopefully have a more recent gid count soon.

I hope to see next summer that venting the garage and staying at a low average SOC does have a clear positive effect!

 

[surfingslovak]

Today I recharged to 100% from 4 miles into VLBW (did not have time to go to turtle).

What was your dash energy economy? Was is below 4 m/kWh?

 

[JeremyW]

Today I recharged to 100% from 4 miles into VLBW (did not have time to go to turtle).

What was your dash energy economy? Was is below 4 m/kWh?

It was 3.9. I went 85.8 miles on that charge.

 

[surfingslovak]

It was 3.9. I went 85.8 miles on that charge.

Great, thank you! Did you reset the economy gauge after the last charge? I believe you might have had about 0.5 kWh usable when you plugged in. My estimate would be about 6 to 8% less capacity, part of which could be due to environmental factors.

 

[JeremyW]

It was 3.9. I went 85.8 miles on that charge.

Great, thank you! Did you reset the economy gauge after the last charge? I believe you might have had about 0.5 kWh usable when you plugged in. My estimate would be about 6 to 8% less capacity, part of which could be due to environmental factors.

I belive so. I think I got the car with ~3.5% loss so even 4% loss in the summer isn't that bad considering we had quite a few days of 100+ degree weather. Tony's car was built two months after mine and is down 10% so I think I'm doing pretty good.

 

[TonyWilliams]

It was 3.9. I went 85.8 miles on that charge.

Great, thank you! Did you reset the economy gauge after the last charge? I believe you might have had about 0.5 kWh usable when you plugged in. My estimate would be about 6 to 8% less capacity, part of which could be due to environmental factors.

I belive so. I think I got the car with ~3.5% loss so even 4% loss in the summer isn't that bad considering we had quite a few days of 100+ degree weather. Tony's car was built two months after mine and is down 10% so I think I'm doing pretty good.

You didn't pound out 30-40 DC quick charges, some of which were at 130F.

 

[TonyWilliams]

It was 3.9. I went 85.8 miles on that charge.

That can't be possible. Nissan says 84 miles at 4.0 miles/kWh !!! Super car !!

Just kidding for all the disbelievers from our PHX range test. We should have had your car in PHX.

 

[TickTock]

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.

You are down 13.73% from the NREL baseline. What instrument did you use to measure the energy from the wall?

 

[TickTock]

Thanks for all the data. I just got back into town and added everything (I think) including the requested % degradation column based on the NREL baseline. If I am missing any information please PM me and I will make corrections. Also, there appears to be a discrepancy in the NREL L2-->Battery efficiency of 86.7% versus Ingineers measured value of 91%.

From-the-Wall Capacity

 

[surfingslovak]

I just got back into town and added everything (I think) including the requested % degradation column based on the NREL baseline. Also, there appears to be a discrepancy in the NREL L2-->Battery efficiency of 86.7% versus Ingineers measured value of 91%.

Great to hear, good to have you back. I've noticed that discrepancy as well, and I believe that Ingineer measured charger efficiency and energy delivered to battery terminals. No consideration was given to any losses within the battery during charge and discharge events (primarily due to heat dissipation).

 

[vegastar]

In my case, the first measurement took place in 2011-07-19, or 12 days after delivery. It was from dead, not turtle and the total energy was 25.12kW.h.

You can find my log here:

https://docs.google.com/spreadsheet/ccc?key=0AvuZhK4s7poqdEJfYTBCb3lwakZDNGI1cGNJUlFIUmc#gid=0

 

[Ingineer]

I just got back into town and added everything (I think) including the requested % degradation column based on the NREL baseline. Also, there appears to be a discrepancy in the NREL L2-->Battery efficiency of 86.7% versus Ingineers measured value of 91%.

Great to hear, good to have you back. I've noticed that discrepancy as well, and I believe that Ingineer measured charger efficiency and energy delivered to battery terminals. No consideration was given to any losses within the battery during charge and discharge events (primarily due to heat dissipation).

I only measured charge efficiency essentially as a "spot-check" with the battery at ~%65 SoC. This was instantaneous (but averaged) wall POWER measured compared to power delivered to the battery. NREL's report claims 86.69% total ENERGY efficiency for a full charge session. They didn't specify which EVSE was used or at what rate, but one would assume they at least used 240v.

Here are my results:

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%

All these measurements were with the Leaf pack at around 62 degrees F and ~65% SoC. Readings were allowed to stabilize before recording. The power to the Leaf battery was calculated by recording amperage at the cell interconnect level using a high-accuracy kelvin-connected current shunt, so the losses are a sum of all EVSE/Charger/Leaf systems. Charger input power was similarly recorded using lab-grade calibrated true RMS equipment, not a Kill-A-Watt.

These efficiency calculations do not take into account the coulombic loss in the Leaf's battery, and other Leaf systems during discharge, so this is only charging efficiency up to the battery pack itself but not including the pack, of which also has notable loss.

I saw a better spot efficiency, but I didn't allow for the taper at the end of the charge. This is inherently less efficient, both for charging and battery efficiency. Also, they probably didn't use one of our upgraded EVSE's, which is more efficient than most wall-mounted 240V units. (Blink, AV, etc) Still, I'm impressed that is was as good as it was in their test.

-Phil

 

[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.

You are down 13.73% from the NREL baseline. What instrument did you use to measure the energy from the wall?

TickTock,
My digital meter next to my 240v outlet only measures 1 k/wh and greater differences unfortunately. It is a Cooper B-Line meter. It goes up 1 k/wh every 15 minutes, so I figured 10 minutes was .66 k/wh. I know that this is not very accurate, but how much can it be off? I figured that because I charged between 48-53 degrees, and I had 5 temp. bars, that there is more energy that I should be able to put into the battery pack when it is 70 degrees out and I have six temp. bars. I charged LBW to 100% twice in September of this year and the temperatures were at lease 70 degrees with 6 temperature bars. Both times, the meter was at around 18 k/wh.