Capacity Loss on 2011-2012 LEAFs

[Stoaty]

Alternatively, those in hot areas considering the purchase of an EV should in my opinion consider a model with liquid battery cooling such as a Ford Focus Electric, a Tesla, or a Chevy Volt. Or just lease (not buy) a LEAF.

I think this is a very reasonable recommendation given the available data on the effect of high temperatures on battery capacity.

 

[Ingineer]

I have found that once a "full" charge is finished, I have found that you can sometimes force more charging (and/or balancing) simply by leaving the EVSE connected and initiating a remote climate control activation through CarWings. Last time I tried this, charging had stopped at 20.2kWh stored with 259 gids showing. After activating the CC, I made it up to 22.3kWh with 280 gids after the climate control shut itself off.

This may be a good way to effect a more accurate capacity measurement if you have a gid meter.

-Phil

 

[GRA]

Alternatively, those in hot areas considering the purchase of an EV should in my opinion consider a model with liquid battery cooling such as a Ford Focus Electric, a Tesla, or a Chevy Volt. Or just lease (not buy) a LEAF.

I think this is a very reasonable recommendation given the available data on the effect of high temperatures on battery capacity.

Or a Coda, which aside from liquid-cooling also benefits from an LiFePo4 chemistry, said to be both more tolerant to heat and to have significantly slower degradation than LiMn2O4. But you have to be willing to take a chance on a startup.

 

[GaslessInSeattle]

anyone have a sense if cycling the battery closer to 50% in hot whether would be beneficial. Could it be that 80% SOC in extreme climates should still be considered "high soc", high enough to be above some depletion threshold that causes accelerated aging.

Alternatively, those in hot areas considering the purchase of an EV should in my opinion consider a model with liquid battery cooling such as a Ford Focus Electric, a Tesla, or a Chevy Volt. Or just lease (not buy) a LEAF.

I think this is a very reasonable recommendation given the available data on the effect of high temperatures on battery capacity.

Or a Coda, which aside from liquid-cooling also benefits from an LiFePo4 chemistry, said to be both more tolerant to heat and to have significantly slower degradation than LiMn2O4. But you have to be willing to take a chance on a startup.

 

[Stanton]

I have found that once a "full" charge is finished, I have found that you can sometimes force more charging (and/or balancing) simply by leaving the EVSE connected and initiating a remote climate control activation through CarWings. Last time I tried this, charging had stopped at 20.2kWh stored with 259 gids showing. After activating the CC, I made it up to 22.3kWh with 280 gids after the climate control shut itself off.

This may be a good way to effect a more accurate capacity measurement if you have a gid meter.

-Phil

Wish I would have tried this when I borrowed the GID meter, but why doesn't simply initiating another charge (via CarWings) have the same effect? Guess I'll have to try these sort of things once I get a LeafScan!

 

[Ingineer]

Wish I would have tried this when I borrowed the GID meter, but why doesn't simply initiating another charge (via CarWings) have the same effect? Guess I'll have to try these sort of things once I get a LeafScan!

No, because it will terminate the charge very soon after initiation. The trick is that when the CC is activated it allows a much longer time with the pack "floating" for extra electrons to "sneak" in.

-Phil

 

[surfingslovak]

anyone have a sense if cycling the battery closer to 50% in hot whether would be beneficial. Could it be that 80% SOC in extreme climates should still be considered "high soc", high enough to be above some depletion threshold that causes accelerated aging.

Personally, I would go with 60% or lower if the car was parked for more than a few hours and it was hot out. The low conservative threshold should be around 30%. That's just for parking. I would not hesitate to charge up to 80%, maybe even to full, if I needed the range and the car did not sit like that very long.

 

[cyellen]

[/quote]Personally, I would go with 60% or lower if the car was parked for more than a few hours and it was hot out. The low conservative threshold should be around 30%. That's just for parking. I would not hesitate to charge up to 80%, maybe even to full, if I needed the range and the car did not sit like that very long.[/quote]

Are you basing your reply on science or just your opinion? Seems like that strategy would leave you with extremely limited range - hardly worth having a car at that point.

 

[abasile]

Personally, I would go with 60% or lower if the car was parked for more than a few hours and it was hot out. The low conservative threshold should be around 30%. That's just for parking. I would not hesitate to charge up to 80%, maybe even to full, if I needed the range and the car did not sit like that very long.

Are you basing your reply on science or just your opinion? Seems like that strategy would leave you with extremely limited range - hardly worth having a car at that point.

Lately we've been parking our car with between roughly 30% and 50% SOC whenever it's at home, and timing it to charge to a higher level just before we need it. This is no problem at all for us because we hardly do any spontaneous drives of more than a few miles; we know ahead of time what we are going to be doing. And we always have enough charge to get to a medical facility in case of semi-emergency.

Nobody really knows how much difference it will make in the long run to "baby" the battery in this manner. Compared to leaving the car sitting at 80%, the difference for most people might turn out to be small.

Maybe this is analogous to keeping the car clean and caring for the paint job. Some folks obsess over this, and others like myself are pretty relaxed. Having a technical bent, however, some of us may choose to obsess over battery care.

 

[RegGuheert]

A charge set to 80% stops at 80% SoC (real SoC, not what Gidmeters report), whereas a "full" charge usually is stopped from 94-95% SoC. So the difference is only ~15% of the total pack capacity. A charge to true 100% SoC would give you about 24kWh, but the battery ECU is more interested in making the pack last long, (or at least attempting to, Sorry Phoenix!) so it never allows that truly "full" charge.

Phil, do you know The SOC of the LEAF battery with 0 GIDs? (Assume a new LEAF with a well-balanced battery pack.)

 

[surfingslovak]

Phil, do you know The SOC of the LEAF battery with 0 GIDs? (Assume a new LEAF with a well-balanced battery pack.)

Please have a look at some of Phil's earlier comments. The main contactor opens when the Gids drop to a value between 4 to 6. The exact timing seems to depend on several factors, of which the voltage sag could be the determining one. I would not be aware of any battery reaching 0 Gids out in the field. In fact, we a have reason to believe that Nissan actively seeks to prevent that to avoid the infamous bricking phenomenon. Hope this helps.

 

[RegGuheert]

Phil, do you know The SOC of the LEAF battery with 0 GIDs? (Assume a new LEAF with a well-balanced battery pack.)

Please have a look at some of Phil's earlier comments. The main contactor opens when the Gids drop to a value between 4 to 6. The exact timing seems to depend on several factors, of which the voltage sag seems to be the determining one. I would not be aware of any battery reaching 0 Gids out in the field. In fact, we a have reason to believe that Nissan actively seeks to prevent that to avoid the infamous bricking phenomenon. Hope this helps.

Thanks! O.K. So Phil states the contractor opens at 2% SOC and you indicate it opens at 4-6 GIDs, then that implies that 0 GIDs equate to 0% SOC.

I accept that an 80% charge equates to SOME fixed SOC, but it seems it is not actually 80%, since 80%/94% <>232/281. I will assume that the charger drives to some temperature-compensated voltage which gets Li somewhere around 80% SOC, but it seems the target is a bit below 80%.

 

[surfingslovak]

I accept that an 80% charge equates to SOME fixed SOC, but it seems it is not actually 80%, since 80%/94% <>232/281. I will assume that the charger drives to some temperature-compensated voltage which gets Li somewhere around 80% SOC, but it seems the target is a bit below 80%.

My best guess is that the relationship between the true SOC (determined by the battery ECU) and stored watt-hours (Gids) is nonlinear.

 

[TonyWilliams]

My understanding is as follows for a new 70F/20C fully charged battery:


-------------------KWH-------Gid------SOC%
Rated capacity: --24 ------- 300 ---- 100
Stored energy: --22.5 ----- 281 ----- 94
Usable energy: --21.0 ----- 281 ----- 94
Depleted cutoff: --0.5 ------ 5 -------- 2


My understanding is as follows for a new 70F/20C fully charged, 50% depleted battery:


-------------------KWH-------Gid------SOC%
Rated capacity: --24 ------- 300 ---- (not possible)
Max possible. : -- 12 ------ 150 ----- 100%
Stored energy: --11.2 ----- 140 ----- 94
Usable energy: --10.5 ----- 140 ----- 94
Depleted cutoff: --0.5 ------ 5 -------- 2

 

[surfingslovak]

-------------------KWH-------Gid------SOC%
Rated capacity: --24 ------- 300 ---- 100
Stored energy: --11.2 ----- 140 ----- 94
Usable energy: --10.5 ----- 140 ----- 94
Depleted cutoff: --0.5 ------ 5 -------- 2

Great post, Tony. Did you mean 50% in the table above by any chance?

I'm just guessing, but the reason I mentioned a nonlinear relationship between Gids and SOC is because I'm aware of two data points that seem to support that: 80% SOC is about 77% on Gid basis (231/300) and full is 94 or 94.5% according to Phil, but only 93.66% on Gid basis.

Another possibility that the battery does not hold exactly 300 Gids when charged to 100% SOC. Following that assumption, 231 Gids and 80% SOC would imply 290 Gids total. If you combined that with 281, a full charge would yield 96 or 97% SOC, which is still off.

 

[Ingineer]

Phil, do you know The SOC of the LEAF battery with 0 GIDs? (Assume a new LEAF with a well-balanced battery pack.)

Zero. Gids are stored watt-hours, not usable watt-hours. Same with SoC, it's the real state of charge, so it will never get to zero, or rather, it never should in the Leaf.

-Phil

 

[TonyWilliams]

-------------------KWH-------Gid------SOC%
Rated capacity: --24 ------- 300 ---- (not possible)
Max possible. : -- 12 ------ 150 ----- 100%
Stored energy: --11.2 ----- 140 ----- 94
Usable energy: --10.5 ----- 140 ----- 94
Depleted cutoff: --0.5 ------ 5 -------- 2

Great post, Tony. Did you mean 50% in the table above by any chance?

I'm just guessing....

Ok, I edited it to clarify the 50% capacity degradation.

 

[Ingineer]

For an 80% charge the Leaf always stops when SoC=80%, but keep in mind this is dependent on the accuracy of the battery ECU's calculation during charging, so there could be some error from charge to charge and/or Leaf to Leaf. (I would imagine temperature as well)

However a "full" charge seems to be usually somewhere from 94-95%, with the Gids varying appropriately. I don't often do many full charges, but I'll begin paying closer attention to my numbers.

Something also to note is that Gids seem to have significant hysteresis. Sometimes they won't "tick" when it seems when they should. I have observed sometimes they won't drop during use for some time even after a few gid's worth of SoC has clearly been consumed, then all the sudden they will play catch up. It is unknown why this is.

SoC always seems to keep up, even when the Gids don't, so I don't trust Gids as much. But conversely, when SoC is corrected, such as on power up, sometimes the Gids will stay the same.

Many mysteries!

-Phil

 

[RegGuheert]

Thanks, guys! I'm with you on all of the above.

Thanks for the tidbit on hysteresis, Phil. Trying to integrate energy into/out of a battery always seems to give some hysteresis given the resistance and the other differences in charge and discharge voltages.

Thanks again!

 

[Boomer23]

Here's another data point.

Blue LEAF
14 months since delivery 3/31/11
Coastal Orange County, CA
I've charged about 26 times per month, almost always overnight with some public charging each month and two QCs. Home charging has been to 100% about 98% of the time. Car is mostly driven smoothly, with early average energy economy on the dash of 3.8 mi/kWh, now averaging 4.0 mi/kWh.
I have not lost a capacity bar. Nissan dealer battery report at 12 months, April 11, was 5 stars on all parameters at 11,600 miles.

80% charge overnight from 163 Gids on 5/29/12: 225 Gids, voltage 387.5, ambient temp at time of reading appx 65 F, overnight low temp 57 F.
100% charge overnight from 77 Gids on 5/30/12: 274 Gids, voltage 394, ambient temp at time of reading appx 64 F, overnight low temps range 59 to 61 F. Charge was done with timer override, beginning about 12:40 am, ending at 5:05 am, with car still plugged in until 8:30 am.

(Temp readings are from iPhone weather app, not recorded temps in garage. Garage is un-insulated flat grey rock roof.)

My car was routinely getting 281 Gid readings after 100% charge, with occasional drops to as low as 278 Gid, but my records show outliers for 100% charges in January of 275, 267 and 271, February's lowest was 278 Gid, March had one reading of 269 Gid after a 100% charge from only 28 Gid, April only one low reading of 275 Gid. May started out with 280 and 281, but started dropping on May 6 with 272 Gid after a 100% charge from 103 Gid. I haven't seen anything above 279 Gid since May 4, with low readings of 272, 274, 274, 275, 272, 272, 276, 273, 269, 275, 270, and today 274.

One other point: I started seeing readings not higher than 278 after May 12, a day when I put 95 miles on the car, having driven to Cerritos and then charged mid-day to be able to do some evening driving. Again, 280 and 281 Gids were reliably routine with my car, the last such reading being May 4.

Some recent data from my LEAF. I'm continuing to see a small decline in Gid readings on both 80% and 100% charges. I changed to doing 80% charges around June 1 to help battery life.

June 1, 80% chg beginning at 104 Gid: 223 Gid, 386 Volts, overnight low temp 63 F
June 2, 80 % chg beginning at 143 Gid: 223 Gid, ? Volts, temp 61 F
June 3, 80% chg beginning at 180 Gid: 223 Gid, 387.5 Volts, temp 61 F
June 5, 80 % chg beginning at 60 Gid: 223 Gid, 386.5 Volts, temp 61 F
June 6, 80% chg beginning at 132 Gid: 222 Gid, 387.5 Volts, temp 57 F
June 7, 805 chg beginning at 178 Gid: 222 Gid, 388 Volts, temp 61 F
June 8, 80% chg beginning at 148 Gid: 221 Gid, 387.5 Volts, temp ?
June 9, 100% chg beginning at 152 Gid: 268 Gid, 393.5 Volts, temp 61 F
June 10, 100% chg beginning at 63 Gid: 270 Gid, 394 Volts, temp 59 F

I did the consecutive 100% charges over the last two nights following Ingineer's advice that a full charge Gid count on a LEAF that is regularly charged to 80% can only be considered accurate after two or more 100% charges. Notice that I'm getting about 3 Gids lower capacity on 80% charges and 4 to 6 Gids lower on 100% charges than in mid May. Both 100% charges were done with no timer set, just plugged in and started charging after midnight and left the car plugged in to 240 V for at least 5 hours.

On today's 100% charge, I even tried Ingineer's advice about initiating a remote climate control session while plugged in, then leaving the car plugged in with timer override. The car did a little bit of charging based on my TED system readings, the blinking blue light on the dash and the indicator on the AV EVSE, but I never regained any Gids. In fact, after two different climate control sessions with the car plugged in and then a bit of charging activity, my Gid count actually dropped to 266.