Capacity Loss on 2011-2012 LEAFs

[Stoaty]

Here is the same data from the Phoenix area one bar losers presented in a slightly different way that drives home the point that racking up miles more quickly leads to quicker loss of battery capacity. I have plotted Miles Driven Per Month vs. Percent capacity loss per month. Linear regression shows:

slope - 831
intercept - 168
correlation coefficient is 0.51 (moderate correlation)

Since miles driven per month means more cycling of the pack per month, it appears that both heat and cycling of the pack are factors in capacity loss:

[myleaf]

Here is the same data from the Phoenix area one bar losers presented in a slightly different way that drives home the point that racking up miles more quickly leads to quicker loss of battery capacity. I have plotted Miles Driven Per Month vs. Percent capacity loss per month. Linear regression shows:

slope - 831
intercept - 168
correlation coefficient is 0.51 (moderate correlation)

Since miles driven per month means more cycling of the pack per month, it appears that both heat and cycling of the pack are factors in capacity loss:

This data is very interesting. It would be nice to see the data from the Leafs that lost two bars, plotted for the interval between the loss of the first and second bar. My limited data shows a 3%/month capacity loss and I believe I am about to lose my 2nd bar.

[ALLWATZ]

there is a lot of hysteria on the board right now and some balance is needed and i dont think that OE's comments are farther out than comments made on the other side. both are rife with speculation and the problem we have is really limited information and no parameters to go by.

so the only thing we can do is continue to gather what information we can, continue to crunch it various ways and see what results.

speculating on how badly Nissan is doing is becoming counterproductive to this forum. i am not saying that the affected should not be unhappy or should not voice their concerns to Nissan but that issue ALONE has made it difficult to sift thru the real value of pertinent information posted here.

Your right that there is a lot of hysteria on the board and why not?
First, the people who live in cool weather climates seem to be the ones who are not effected and posting comments that enrage the ones who have had losses and are being stonewalled by Nissan. Maybe they should self sensor their comments or perhaps say to themselves "what would Jesus say online". I'm not saying they shouldn't have an opinion but, hysteria like all things, don't exsist in a vacuum! There were plenty of Pinto owners who loved and defended their cars and were perfectly fine as long as they didn't get rear-ended.
Second, as far as being counterproductive, if Nissan is not going to admit they have a problem publicly, any advice that could be vetted here (oh yes I did say vetted in an election year) will be appreciated by those of us who do have real problems and might lead to a short term remedy. Also, when Nissan comes out with their "secret warranty" (http://www.autosafety.org/secret-warranties" onclick="window.open(this.href);return false;) to those people in the Phoenix area, it will be nice for those of us who live in CA and TX to find out about it here first.

[edatoakrun]

High miles per month would also be generally indicative of those battery packs that tend to be cycled from very high to very low states of charge, and/or are heated, by frequent mid-day recharging, above those temperatures caused by ambient conditions.

So I think that the correlation of loss of capacity and cycling that you point out, could actually be, in part or in all, only coincidental.

Here is the same data from the Phoenix area one bar losers presented in a slightly different way that drives home the point that racking up miles more quickly leads to quicker loss of battery capacity. I have plotted Miles Driven Per Month vs. Percent capacity loss per month. Linear regression shows:

slope - 831
intercept - 168
correlation coefficient is 0.51 (moderate correlation)

Since miles driven per month means more cycling of the pack per month, it appears that both heat and cycling of the pack are factors in capacity loss:

[Stoaty]

High miles per month would also be generally indicative of those battery packs that tend to be cycled from very high to very low states of charge, and/or are heated, by frequent mid-day recharging, above those temperatures caused by ambient conditions.

So I think that the correlation of loss of capacity and cycling that you point out, could actually be, in part or in all, only coincidental.

Agreed. It could be higher depth of discharge, being left at high SOC for longer periods of time in order to do a longer commute, heating from mid-day recharging, etc. The main thing is that this is the first time I have found a correlation that suggests that calendar loss from high heat is not the only factor; something about the battery cycling seems to be involved also.

[Pipcecil]

I am curious as well why our gauges are 5% off, respecitively ~5% lower for each and every car. This could be the "software" bug that has been floating around on this thread. Regardless, that still doesn't address the accelerated loss occuring (it may not be as extreme but it is still significant). I am extremely afraid Nissan is counting the ~7% of our battery that cannot be accessed. To me, its very misleading to include that total since we would never be allowed to use it! But thats only speculation, and we can't verify that at all.

I do know that since I have owned the car, I am experiencing ~15-20 miles reduced capacity from new. That is with improved driving habits (finally hit 4 mi/kWh last month for lifetime average!), a very mild north Texas summer, and more chances to pre-cool/heat to extend my range. If I had retained the same level, I would be getting more range now. If I had lost only a few %, I think I would be having the same range with better "oustide" factors.

An interesting idea that occured that could relate to quicker degredation is "topping off" I am not aluding to plugging in the car to charge if 80% or greater capacity remains (something the manual advises to mimimize), but the use of the heating and cooling, especially on a 100% charged car. Everyone here knows that instead of creating a dedicated circuit to handle power from the outside source to run the A/C or heater, the LEAF uses the default set-up and pulls energy from the battery itself while the outside line recharges the battery. I recognize this when I precool my car in the morning for about 25 minutes with a the Level 1 (my wife uses the Level 2 for the volt). I am actually down some power (my time to charge will range from 10-40 minutes via Level 2 on the dash), once I was even down an addition fuel bar when I leave. If "topping off" is not ideal, why have this setup with easy access to climate control your car and encourage it to extend range!

It could be a compounded problem as the heat + the topping off occuring from using the CC together causes extra degradation? Its only a guess. If this was a greater factor than the heat (I doubt it) a proof of concept would be vehicles in extreme cold climates seeing battery loss from this next winter (cars would be a year+ by then too). If the idea does not hold clout then they will all drive happily to and from work!

[Volusiano]

High miles per month would also be generally indicative of those battery packs that tend to be cycled from very high to very low states of charge, and/or are heated, by frequent mid-day recharging, above those temperatures caused by ambient conditions.

So I think that the correlation of loss of capacity and cycling that you point out, could actually be, in part or in all, only coincidental.

Agreed. It could be higher depth of discharge, being left at high SOC for longer periods of time in order to do a longer commute, heating from mid-day recharging, etc. The main thing is that this is the first time I have found a correlation that suggests that calendar loss from high heat is not the only factor; something about the battery cycling seems to be involved also.

Of course heat is not the only factor. But it must be the biggest factor.

I assume that the 20% loss over 5 years as predicted by Nissan is mainly cycling loss. Anything more than this is probably due to other factors, but heat is the biggest factor.

[TonyWilliams]

I am curious as well why our gauges are 5% off, respecitively ~5% lower for each and every car. This could be the "software" bug that has been floating around on this thread.

Where do you get this? What gauge are you referring to? The capacity gauge can be set to any value Nissan intends; that's not "off". The current misleading values are 15% reduction for the first bar, which fairly well correlates to the observed Gid count, then either 6 or 7% for the remaining bars. The two values, Gid wattHours, and battery capacity, are measured and calculated differently (so the magic software problem would have to affect both).

Again, Nissan is going to say virtually ANYTHING except their cells can't handle the heat.

[GaslessInSeattle]

I have pondered this too, wondering if that design wouldn't backfire. hmm, yet another question for the wiki: frequency of using pre cooling at 100% SOC. I saw this mostly with prewarming on my first leaf. It appeared that prewarming after a 100% charge would allow the battery to get overcharged some, resulting in greater range, though I didn't have a gid meter to verify. I started timing the prewarming from a 80% charge and did a variety of experiments prewarming from 80% to 100% charge to attempt to raise the core temp of the battery in cold weather. while I did not want to overcharge the battery, I did find that prewarming for extended periods, from 80% SOC would warm the battery some and return some of the lost cold weather range.

If I lived in Phoenix or other areas with extreme heat, I'd do some experimenting with precooling from 80% or lower for extended periods and see if you can lower the temp of the battery or at least keep it from getting so high (wish we had the Leafscan to actually see the battery temp!). the car would of course have to be kept plugged in. conversely, I'd avoid precooling from a 100% charge in hot climates, as I am quite sure this allows for the battery to take on some excess voltage. super high heat and extra high SOC would likely compound the rate of degredation.

I am curious as well why our gauges are 5% off, respecitively ~5% lower for each and every car. This could be the "software" bug that has been floating around on this thread. Regardless, that still doesn't address the accelerated loss occuring (it may not be as extreme but it is still significant). I am extremely afraid Nissan is counting the ~7% of our battery that cannot be accessed. To me, its very misleading to include that total since we would never be allowed to use it! But thats only speculation, and we can't verify that at all.

I do know that since I have owned the car, I am experiencing ~15-20 miles reduced capacity from new. That is with improved driving habits (finally hit 4 mi/kWh last month for lifetime average!), a very mild north Texas summer, and more chances to pre-cool/heat to extend my range. If I had retained the same level, I would be getting more range now. If I had lost only a few %, I think I would be having the same range with better "oustide" factors.

An interesting idea that occured that could relate to quicker degredation is "topping off" I am not aluding to plugging in the car to charge if 80% or greater capacity remains (something the manual advises to mimimize), but the use of the heating and cooling, especially on a 100% charged car. Everyone here knows that instead of creating a dedicated circuit to handle power from the outside source to run the A/C or heater, the LEAF uses the default set-up and pulls energy from the battery itself while the outside line recharges the battery. I recognize this when I precool my car in the morning for about 25 minutes with a the Level 1 (my wife uses the Level 2 for the volt). I am actually down some power (my time to charge will range from 10-40 minutes via Level 2 on the dash), once I was even down an addition fuel bar when I leave. If "topping off" is not ideal, why have this setup with easy access to climate control your car and encourage it to extend range!

It could be a compounded problem as the heat + the topping off occuring from using the CC together causes extra degradation? Its only a guess. If this was a greater factor than the heat (I doubt it) a proof of concept would be vehicles in extreme cold climates seeing battery loss from this next winter (cars would be a year+ by then too). If the idea does not hold clout then they will all drive happily to and from work!

[DesertDenizen]

Scott Yarosh, (down to nine capacity bars), told me yesterday he did a 100% charge, drove 28 miles, and returned home with only two SOC bars remaining. Not a viable vehicle anymore.

My dealer called me this morning and said he was in touch with "Nissan engineers". He was told they were looking into the problem. At least they referred to it as 'a problem' and not a normal phenomenon.