"Verifiable" Normal Battery Degradation

[Weatherman]

I'm not seeing any temperature adjustment to available capacity, either.

When I swapped my old LEAF for a new one in early July, it was obvious there was a difference in available battery capacity. That hasn't changed over the past month. The battery on the new LEAF is happily providing about 21 kWh of available energy even with temps in the 80s and 90s, while the old one seemed lucky to provide about 18 kWh.

 

[DaveinOlyWA]

I'm not seeing any temperature adjustment to available capacity, either.

When I swapped my old LEAF for a new one in early July, it was obvious there was a difference in available battery capacity. That hasn't changed over the past month. The battery on the new LEAF is happily providing about 21 kWh of available energy even with temps in the 80s and 90s, while the old one seemed lucky to provide about 18 kWh.

oh there is definitely temperature adjusted capacity. the only question is the mechanics of how it happens. what appears to happen is that the car has to maintain a sustained temp over a time period before any adjustment happens. guessing that in our moderate areas the adjustment is simply too small to really measure or maybe non-existent

 

[Weatherman]

oh there is definitely temperature adjusted capacity. the only question is the mechanics of how it happens. what appears to happen is that the car has to maintain a sustained temp over a time period before any adjustment happens. guessing that in our moderate areas the adjustment is simply too small to really measure or maybe non-existent

That is possible. When I bought the new one, it had been sitting in the dealer's showroom at a nice, cool, 72F. The battery temperature showed 5 bars, which is something I rarely see. Over the past month, the battery has been exposed to mean temperatures closer to 86F (low 90s during the day and upper 70s at night). As I remarked elsewhere, South Florida is warm, but it isn't "Phoenix warm".

 

[DaveinOlyWA]

oh there is definitely temperature adjusted capacity. the only question is the mechanics of how it happens. what appears to happen is that the car has to maintain a sustained temp over a time period before any adjustment happens. guessing that in our moderate areas the adjustment is simply too small to really measure or maybe non-existent

That is possible. When I bought the new one, it had been sitting in the dealer's showroom at a nice, cool, 72F. The battery temperature showed 5 bars, which is something I rarely see. Over the past month, the battery has been exposed to mean temperatures closer to 86F (low 90s during the day and upper 70s at night). As I remarked elsewhere, South Florida is warm, but it isn't "Phoenix warm".

ya, i think the upper end of TB 6 is when the degradation curve starts to get steeper but as long as you never see 7 TBs you will have degradation but it should be very slow like less than 3-4 % over 12 months or 12,000 miles

 

[DaveEV]

ya, i think the upper end of TB 6 is when the degradation curve starts to get steeper but as long as you never see 7 TBs you will have degradation but it should be very slow like less than 3-4 % over 12 months or 12,000 miles

As WetEV pointed out earlier, battery degradation rate should follow the Arrhenius equation which approximates a doubling of calendar life for every 10C reduction in temperature.

If we consider 68F / 20C ideal and lasts 1 lifetime, then these temps result in

122F / 50C = 1/8 lifetime
104F / 40C = 1/4 lifetime
86F / 30C = 1/2 lifetime
68F / 20C = 1 lifetime
50F / 10C = 2 lifetimes
32F / 0C = 4 lifetimes
14F / -10C = 8 lifetimes

1 summer month in Phoenix is probably like 10 months in Seattle!

It would be nice to have a calculator and be able to plug in a location and get a "battery calendar life constant" - one could then plug in a location and compare expected calendar life compared to a constant 68F/20C.

 

[WetEV]

It would be nice to have a calculator and be able to plug in a location and get a "battery calendar life constant" - one could then plug in a location and compare expected calendar life compared to a constant 68F/20C.

I'm sure someone with more time will write one. Otherwise I'd have to...

High temperature matters more than low or average daily. Summer matters more than winter...

I'm wondering if a fan pulling cool outside air into the garage at night for the few months of warmer than 68F/20C high temperatures matters enough to pay for the fan even in Seattle area. It might. It would be nice if the battery calendar life calculator would include the effects of such modifications. And the effects of thermal battery management as well. Sounds like a cool application.

 

[surfingslovak]

High temperature matters more than low or average daily. Summer matters more than winter...

I would really like to see such statements backed up with hard data. Numbers, graphs and degradation models please. Only then we can correlate what you say to the data coming from the field.

 

[WetEV]

High temperature matters more than low or average daily. Summer matters more than winter...

I would really like to see such statements backed up with hard data. Numbers, graphs and degradation models please. Only then we can correlate what you say to the data coming from the field.

Surfingslovak has a point. Probably should have said something more like this:

Based on the Arrhenius equation approximation, I would expect that high temperature probably matters more ...

Data trumps theory.

 

[DaveinOlyWA]

double post

 

[DaveinOlyWA]

ya, i think the upper end of TB 6 is when the degradation curve starts to get steeper but as long as you never see 7 TBs you will have degradation but it should be very slow like less than 3-4 % over 12 months or 12,000 miles

As WetEV pointed out earlier, battery degradation rate should follow the Arrhenius equation which approximates a doubling of calendar life for every 10C reduction in temperature.

If we consider 68F / 20C ideal and lasts 1 lifetime, then these temps result in

122F / 50C = 1/8 lifetime
104F / 40C = 1/4 lifetime
86F / 30C = 1/2 lifetime
68F / 20C = 1 lifetime
50F / 10C = 2 lifetimes
32F / 0C = 4 lifetimes
14F / -10C = 8 lifetimes

1 summer month in Phoenix is probably like 10 months in Seattle!

It would be nice to have a calculator and be able to plug in a location and get a "battery calendar life constant" - one could then plug in a location and compare expected calendar life compared to a constant 68F/20C.

i think you are on the right track but the scale is probably not right.

if we look at 5 bars being 4% degradation over 5 years.

6 bars being 8%
7 bars being 16%
8 bars being 32%
9 bars being 64%
10 + bars 128%

but i think that rate of degradation only applies to the top portion of the battery so after you lose "X" percent, (any guess on when the rate starts to taper off?? i say between 10-15%) the rate drops off so you would see a bell curve

what i would like to see if a digital temp bar just to see how much charging, driving, etc. makes a difference

 

[GaslessInSeattle]

Dave, I have been wondering the same thing. With Tony's new lease and another year or so even without testing the turtle on a regular basis for the range chart I suspect we will see a similar level of degradation due simply to clocking so many hours at a higher ambient temp than us in the PNW. With others in San Diego reporting significant loss in one year, it makes me think that while turtle is not generally advised, it may be too early to say it's the culprit for his range loss... certainly I could be wrong. As for a magic number, I suspect it's just "the lower the better" rather than a magic temp threshold. and as for it tapering off, the most startling thing to me is seeing that it doesn't seem to taper off, if anything, it picks up speed, though we don't have enough 3 and 4 bar losers yet to really discern a solid pattern. So far, I see no indication that Nissan's assertion is correct, in fact, I think it's possible that Nissan simply borrowed a play from the Tesla/roadsters game book, crossing their fingers that it applied to the Leaf. Roadster owners have confirmed a tapering off occurs, but don't forget, that's with TMS. As you have noted, the Leaf without TMS may only be suitable in a narrow range in the US. TMS would help the winter time range loss and protect the battery in the summer, even in WA, where some parts get quite cold/hot.

As for my car, I have little useful data to share. I traded up about 6 months ago. I suspect my gid count started out a little low with the new Leaf but I don't have a meter and have been holding out for the Leafscan. My house is a bank home, the garage is in the bank, surrounded by cool dirt, it's quite nice for the Leaf which will end up spending most of it's life in the 30-60 degree range, year to year. Honestly though, I'm uncomfortable with driving the Leaf to areas of WA or OR that are hot, it's just too much of a wild card at this point and having to worry about it so much is seriously a drag. My conclusion is that TMS is critical to EV's regardless of geography if for no other reason than for peace of mind and that Nissan screwed the pooch royally on this one, pretty much across the board. the notion that Nissan knowling went with an outmoded cheap battery technology is actually starting to sound more plausible as it's just hard to imagine that a basic level of testing wouldn't have turned up these problems, problems that practically everyone else putting out EV's predicted.

Do I interpret this correctly that you have 2% degradation at 18 months? That bodes pretty spectacularly for the longevity of the Leaf, or am I missing something?

Overlooking something...PNW location.

actually the thing overlooked is when does heat become critical. i contend it to be 30C or 86F. look at Tony's car. 5,000 more miles and slightly warmer temps. even if 5% is temporary loss due to temps, he still had another 10% loss to deal with verses my 2%. so am i to lose another 8 % in the next 5,000 miles then have the loss taper to 2% a year? that might happen.

but i think Tony can attribute his loss to more trips to Turtle. i dont think that any other level including VLB is something to worry about. His case is a perfect example that temperature is only part of it. considering the fragility of the pack; Nissan may be marketing a car nationwide that is only viable to less than half the population. Only time can tell with others in his neighborhood.

i have lost track of them which is why i started this thread. is there ANYONE from San Diego who has had their car at least 15 months, has 15,000 miles or more and has any loss to report no matter how small?

 

[DaveinOlyWA]

I honestly think that we can gather enough data to get a decent picture of what we can expect. Waiting anxiously for taylorsf info. I wish he had a GID meter so we could get regular reports on his degradation. At 50,000 miles he should give us a great picture. Bnow he has seen 7 TBs this summer after he started quick charging and stated he had not noticed any range loss until that time...

 

[TonyWilliams]

I put this in the wrong thread earlier:

 

[Caracalover]

Not as scientific a report as you would like here, but thought it might be helpful anyway.

I have 19.500 miles now, and drive into some extreme temp areas almost weekly.

Majority of the time I charge to 80%, and try to avoid a low battery warning through adjustments to my driving. I love to recapture energy, so I utilize N and Eco to slow the vehicle, but D to accelerate. I typically stay with traffic or leave it behind. At work I park in full sun from 7:30 AM till 4 PM on black asphalt in downtown Burbank. Some days both this year and last were over 100 degrees, with many at 90 or more.

Sunday driving is where I have real fun with the Leaf, taking it over a large mountain to the high desert, charging it to 100% the night before and then recharging it to 100% to return home. The typical distance is 65 miles one way, and I arrive close to the first LBW - sometimes above, sometimes below. Home travel never see LBW as it is an elevation drop of more than 1000 feet. Half of the trip is mountain roads which I take the uphill at 35 or so (Try to keep the energy draw at or below 20KW), and the downhill at 45 or a little more depending on the road, how much time I have, or my desire to gain energy - something I just love about the Leaf, and it still hasn't gotten old. Point to that is I am fast charging on the downhills, often at rates of 15kw+ for 5 - 10 minutes.

Last Sunday, the car thermometer read 103 when I got in to return home, and the TB read 6. With the AC on and driving 55 - 68 MPH, the temp bars went to 7 and remained there until I got home. The next day the temp was again at 6. I always recharge the car as soon as I arrive at the destination (Rosamond -wildcatzoo.org No public charging) and it is typically finished before 1PM. I leave around 4PM so it has a full charge for a few hours in the hottest part of the day.

I do not worry about the battery. Last year this may have happened a few times as well. Seems like a certainty although I was not watching then. Watching now due to AZ information.

I have ran the car to empty once. I forgot my charge cord on Sunday, and made it to within 15 feet of the charger in Palmdale when the car quit. My fault, not the cars - it went 29 miles further than my intended destination. Likley broke the 100 mile mark.

I have seen the second low battery warning a few times, always on cold rainy/snowy days. Don't recall turtle except the one time stretching to the Palmdale charger. Yes I have seen snow on my Sunday drive more than once, always made the drive interesting, since this is a road they close (Had to detour once.) in bad weather. The Leaf handled well although we did limit the defroster use on these runs.

While I may have some battery degradation, it is not something I am concerned with at this time, nor has it prevented me from using it on Sundays. I have no real intrest in a GID meter, but do now look more at the status bars to see if the top one has gone away - it hasn't. Software updates have made any data on the charge bars unreliable. I am assuming the LBW still comes on at the same SOC, somewhere around 17%.

 

[TonyWilliams]

I am assuming the LBW still comes on at the same SOC, somewhere around 17%.

Yep. Every version retained the same energy data points for LBW and VLB. Even if the battery capacity bars were at 50%, with a full charge showing 12 fuel bars, that LBW will come on with maybe several (like 3 or 4) fuel bars. It should still be 17% of the new battery available power.

 

[DaveinOlyWA]

https://docs.google.com/spreadsheet/ccc?key=0ArmkVCszTek9dC16a1Q4MjYxNHdJOWJva2s3NGViSnc" onclick="window.open(this.href);return false;

TaylorSF is pretty much the mileage king and I loaned him my SOC meter for time so he could record his commute data. i went ahead and put it in a spreadsheet. let me know if anyone has problems seeing it. its public so shouldnt be.

i had planned on putting it in different thread but the search function came up with nothing