Capacity Loss on 2011-2012 LEAFs

[surfingslovak]

Will also be interesting to see what voltage your pack reads, too. Also, are you able to record time to charge and kWh used to charge? Is it also worth charging to 80% first, recording data and then charging the rest of the way and recording that data, too? (GIDs, voltage, time to charge, energy to charge)

Dave, you can see some of this data in the spreadsheet TickTock posted on the forum a while ago. He is getting 224-225 Gids on a full charge with ~ 393V pack voltage.

 

[LEAFfan]

I live in Phoenix and still have all 12 bars (for now). I have about 9500 miles after receiving the car on May 20, 2011. The car is typically charged to 80% with only the occasional 100% charge (maybe 20 in the past 12 months).
I am attempting to minimize the heat effect by setting my timer to begin charging at 3 am, which I figure results in the coolest period of time in my garage to charge. Been doing that pretty much since delivery.
Since our daily RT commute is only about 20-25 miles, it doesn't need a lot of time to charge to 80%. Never have QC'd and don't really plan to unless it is absolutely necessary.
The car is rarely, if ever, parked out in the sun. My wife and I both have big shady (though not necessarily cool) parking garages at work.

You may not have lost a capacity bar, but I'm willing to bet you have lost some capacity, maybe 10%-12% like mine. I have about the same mileage and time (June) as yours. You must not have a gauge so if you want me to test yours, it will show you pretty closely how much you have lost.
If there is anyone else in the Phoenix area that doesn't have one and wants to see how much they've lost and how close you are to losing a bar, just let me know.

 

[leafkabob]

I live in Phoenix and still have all 12 bars (for now). I have about 9500 miles after receiving the car on May 20, 2011. The car is typically charged to 80% with only the occasional 100% charge (maybe 20 in the past 12 months).
I am attempting to minimize the heat effect by setting my timer to begin charging at 3 am, which I figure results in the coolest period of time in my garage to charge. Been doing that pretty much since delivery.
Since our daily RT commute is only about 20-25 miles, it doesn't need a lot of time to charge to 80%. Never have QC'd and don't really plan to unless it is absolutely necessary.
The car is rarely, if ever, parked out in the sun. My wife and I both have big shady (though not necessarily cool) parking garages at work.

You may not have lost a capacity bar, but I'm willing to bet you have lost some capacity, maybe 10%-12% like mine. I have about the same mileage and time (June) as yours. You must not have a gauge so if you want me to test yours, it will show you pretty closely how much you have lost.
If there is anyone else in the Phoenix area that doesn't have one and wants to see how much they've lost and how close you are to losing a bar, just let me know.

It will be interesting to see when I lose my first bar. In addition to only charging to 100% when necessary, I have tried to be careful to not charge in the heat, park in the heat, or even to QC.

I have often wondered about my gid total ever since TickTock got his gauge. Every time I read his posts I wondered how many of us were in the same boat but weren't aware of it. Although I can't compare today's number to a year ago's number (since I don't have that number), it would satisfy my curiosity. How would you propose taking the reading, stopping by my house after I have charged to 80% or 100%?

 

[shrink]

Although I can't compare today's number to a year ago's number (since I don't have that number), it would satisfy my curiosity. How would you propose taking the reading, stopping by my house after I have charged to 80% or 100%?

I'm in central Phoenix, too, and would be happy to be another data point. We bought our LEAF on 8/6/2011 and it had less than 10 miles on it when we took it home. We mostly charge to 80%; 100% maybe once every month or two. We are not as diligent about the heat, but have OC'd only once.

PM me when you guys decide to take a reading.

 

[LEAFfan]

How would you propose taking the reading, stopping by my house after I have charged to 80% or 100%?

Yes, I could stop by after you charge to 80%/nine or ten bars (should show 79-80%) with your L2. After we take that reading, you could charge on up to 100% which the gauge should then show 94-95% if you have no loss of capacity.

 

[Herm]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

 

[mwalsh]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

Not so. Allowing the charge to stop by itself at "10 out of 12 bars" only resulted in 201 Gids for me this weekend.

 

[LEAFfan]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

Not so. Allowing the charge to stop by itself at "10 out of 12 bars" only resulted in 201 Gids for me this weekend.

+1 Same with my gauge except it will read close to the actual SoC% instead of the Gids. It used to read 80% for an 80% charge, but now it's around 71-72%. A 100% charge was only 78% which used to be 94-97. In almost a year, I've only hit 100% one time after charging on L2.

 

[surfingslovak]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs

Not so. Allowing the charge to stop by itself at "10 out of 12 bars" only resulted in 201 Gids for me this weekend.

Same with my gauge except it will read close to the actual SoC% instead of the Gids. It used to read 80% for an 80% charge, but now it's around 71-72%.

Yes, we have seen this with Stoaty and TickTock as well. Mike, I realize that others have asked already, but your battery seems to have seen better days as well. You would be the only case outside of Phoenix and Austin with approximately 10% capacity loss. I believe that everyone else is 5% or under. Some of us are still within 1% of nominal capacity. It would be interesting to find out what drives these differences.

 

[TonyWilliams]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

No, not right.

 

[TickTock]

100% from turtle got me to 236 GID last night

Not bad for having lost a bar. I got down to 239 last October and never lost a bar. Mine disappeared when my 100% charge was only reaching 225.

 

[TickTock]

Although I have no doubt I am down from last year, the capacity does appear to be following a seasonal fluctuation of around 30 gids.
The red points in the graph are gids*.08 (kwH) after a 100% charge. Blue is the same for 80%. It looks like we may see some return of capacity after summer ends. Am looking forward to October so I can see how I compare to last year.

Available energy in the graph is (miles_driven+GOM_remaining_range)/efficiency recorded at the end of each day (as long as the GOM was < 30 to limit the inaccuracy of the GOM). So this is roughly the usable battery capacity.

 

[edatoakrun]

Although I have no doubt I am down from last year, the capacity does appear to be following a seasonal fluctuation of around 30 gids.
The red points in the graph are gids*.08 (kwH) after a 100% charge. Blue is the same for 80%. It looks like we may see some return of capacity after summer ends. Am looking forward to October so I can see how I compare to last year.

Available energy in the graph is (miles_driven+GOM_remaining_range)/efficiency recorded at the end of each day (as long as the GOM was < 30 to limit the inaccuracy of the GOM). So this is roughly the usable battery capacity.

Thanks for this report.

TickTock's battery performance was an outlier from the beginning, and I think using GOM as a remaining charge indicator is probably only valid IF the energy consumption on different charges is very consistent.

I think that the seasonal variation hypothesis might be born out by future observations, and the near-hysteria on the several threads over the last few days, may turn out to be somewhat overblown.

All LEAF batteries probably begin to lose capacity shortly after manufacture. While I can't confirm the level of loss on my car yet, I'd be very surprised, if some loss does not exist.

The timing of these recent bar disappearances could also reflect LEAF battery management, so both the 11 bar reports,and the recent rapid drops in Gid counts to 100% charge reported by a few, could be somewhat misleading, as to actual battery capacity.

Is "full" for the 11 bar LEAFs (100%) still 94-95% of total capacity (AFAIK, only Phil has reported the ability to measure this, right?) or are the Phoenix LEAFs perhaps protecting their batteries from future damage, due to the rising seasonal temperatures, by restricting the available charge percentage at the "100% charge" setting?

Maybe once a LEAF battery loses a smaller percentage of total battery capacity, battery management kicks in to limit charging levels, particularly at high temperatures (which I assume Phoenix has seen recently), to slow future degradation of capacity. This could explain the sudden bar and100% charge Gid loses.

11 bars might be accurately reflecting a reduction in availability of the "top" of the battery, not that total capacity has declined 15%, and so not present such a scary future prospect.

Try charging to "80%", see how they correlate to temperature, and what kind of reductions you get, from your Gid counts at 80% last year.

If this reduction is found to be consistently well below 15%, we all might find those results reassuring.

 

[LEAFfan]

There's no way at 11 capacity bars that it will be even close to 94-95%. I know my SoC gauge isn't exact, but I'd be willing to bet that it's damn close. Basing it on 281 is not much different than actual SoC%. Right now, I have a 10-12% capacity loss and the SoC shows only about 78-79% after a 100% DCQC. Using L2, it may charge to a little more. A long time ago, after charging to 100% with L2, it did reach 100% ONE time, but mostly was between 93% and 97%. With DCQC, it used to reach 93-94%, but now it shows less than 80% after a 100% charge.
But it will be interesting to see if the capacity losses level off in the next couple years or so.

 

[Ingineer]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

This is not correct. Gids are Stared Watt-Hours, so a battery at 50% capacity as new would read about 140 gids full and 115 gids at 80%. When set to 80% charge, the Leaf halts charging precisely at 80% SoC.

-Phil

 

[Ingineer]

There's no way at 11 capacity bars that it will be even close to 94-95%. I know my SoC gauge isn't exact, but I'd be willing to bet that it's damn close. Basing it on 281 is not much different than actual SoC%. Right now, I have a 10-12% capacity loss and the SoC shows only about 78-79% after a 100% DCQC. Using L2, it may charge to a little more. A long time ago, after charging to 100% with L2, it did reach 100% ONE time, but mostly was between 93% and 97%. With DCQC, it used to reach 93-94%, but now it shows less than 80% after a 100% charge.
But it will be interesting to see if the capacity losses level off in the next couple years or so.

You DO NOT have an SoC gauge, because the number you read is based on watt-hours after some math. If your capacity drops, then the watt-hours drop. You can still have a maximum state of charge regardless of capacity. Thus, a car with 50% capacity would read roughly 50% SoC on your scangauge even if fully charged, even though you'd still 12 SoC bars (6 capacity bars), and Carwings would still show 100%.

If I were you, I'd reprogram the formula on your Scangauge's Xgauge to read watt-hours (multiply by 80) or gids (no math needed), because calling it SoC is wrong.

-Phil

 

[mwalsh]

You would be the only case outside of Phoenix and Austin with approximately 10% capacity loss. I believe that everyone else is 5% or under. Some of us are still within 1% of nominal capacity. It would be interesting to find out what drives these differences.

But I'll reiterate from elsewhere in this thread...this doesn't seem to be translating to any noticeable loss in available range - I'm still arriving home with more or less the same amount of remaining energy as I've seen for the entire ownership period. It would be interesting to take the pack down to VLB to see if the bottom-of-pack, non-linear consumption has accelerated any - that could theoretically be were any loss of range might be hiding. But without doing that, I honestly don't see any negative effects from what's happening as of yet.

And that gives me an opening to post my numbers from yesterday:

0 miles / 90.3 / 254 Gids / 393 v
30.5 miles / 59.4 / 167 Gids / 378 v
61 miles / 29.1 / 82 Gids / 365 v

Edit: Actually, I do see something happening in those numbers. Back when I first got my Gidometer, I would notice that I typically expelled more energy driving to work than I would driving home. I would set off with, say, 97% "SOC" and it would typically take me 40% worth to get to the office. I put this down to non-linear consumption from the top of the pack (due to limited regen?). What I'm seeing now is that it's only taking me ~30% to get to work, which is pretty typical for 30 miles worth of driving at 65mph where the discharge is more linear.

 

[Herm]

What does taking a GID reading at 80% prove?.. its always going to read 231 GIDs, a 100% charge followed by several hours of balancing will give you the maximum capacity, and that is what everyone is interested in. Voltage wont tell you much, it will always read 4.1V per cell when fully charged, no matter how deteriorated the cells are.

This is not correct. Gids are Stared Watt-Hours, so a battery at 50% capacity as new would read about 140 gids full and 115 gids at 80%. When set to 80% charge, the Leaf halts charging precisely at 80% SoC.
-Phil

GIDs are just the stored Ah times the voltage (unless you lied to me ).. a slightly degraded cell looks like a new one (ignore the increased internal resistance for now), still charges to 4.2V but now holds less Ah of capacity. Thus a worn cell with 50Ah remaining at 3.9v should still have the same GID (watts-hour, energy) value as a new cell at the 50Ah level at 3.9v, yet the worn cell will not as many Ah at 4.2V as the new one.

It seems Nissan will warrant against increased internal resistance, so they must feel they have that under control.

 

[RegGuheert]

Although I have no doubt I am down from last year, the capacity does appear to be following a seasonal fluctuation of around 30 gids.

While I will assume that it is temperature-compensated, does anyone know if the Hall-effect current sensor used in the LEAF reads low when it is hot?

 

[vegastar]

I should be temperature compensated. My LEAF is showing slightly HIGHER gid readings at 100% charge (2-3 gids) now that the weather is warming up (for the first time this year I got 6 temperature bars in the morning), wich is expected as a warmer battery can hold more energy. Today 278gids@393V, 24500km or 15300miles.