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Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 12:26 pm
by 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.
Pipcecil wrote: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!

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 12:40 pm
by 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.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 12:51 pm
by Stoaty
myleaf wrote: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.
OK, by popular demand, here it is: ;)

Image

Relevant stats:

Second bar lost in 40-75 days after first bar lost. Mean time - 52.7 days, std dev - 9.7 days
Second bar lost in 800-3800 miles after first bar lost. Mean number of miles - 2095, std dev. - 864
Capacity loss per month ranged from 2.5% - 4.7%. Mean capacity loss per month - 3.7%, std dev. 0.6%

Miles/month vs. Capacity loss/month - correlation coefficient 0.10

Miles vs. Capacity loss/month - correlation coefficient 0.39 (I am not posting a graph because the correlation is in the wrong direction--the fewer miles you drive, the faster you lose capacity). This doesn't make sense, and the correlation coefficient is probably too low to consider there is much correlation.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 12:52 pm
by LEAFfan
OrientExpress wrote:It looks like all of these cars are high mileage ones, ie. more than 15k a year.
I talked to some guy last night at a QC station who told me he just lost his second bar at around 9000 miles/1 year.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:12 pm
by Adrian
Received an attorney advertisement in the mail today regarding Nissan Leaf battery problems. I leased, and as long as the car meets my needs I probably won't consider this option though I have to say loosing a bar at 24k miles in Orange County annoys me. I know I charge twice a day, but there is the example of the gentleman that is at 50k miles and charges twice a day and has not lost a bar yet. I know I said in my previous post I drive 80 MPH, but thinking about it, that's not really accurate. I drive 80 MPH when traffic allows, which is probably less than half the time during my morning and afternoon commute on the HOV lane. If anyone else is interested however, the website mentioned in the letter is http://www.nissanleafproblems.com" onclick="window.open(this.href);return false; and the email was leafbattery@initiativelegal.com . The firm is in LA.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:17 pm
by DarkDave
Count me as another low-mileage 2 bars lost owner. I lost my 2nd bar last week at ~9950 miles. It was almost two months after loosing my 1st bar on 6/15. I've had my Leaf now for almost 18 months.

Interestingly enough, the drop in temperatures the past couple of days has allowed for an increase in charging capacity. This past Wednesday I only got 171 gid on an 80% nightly charge, and yesterday and today with the lower temps, I was able to get 181 and 182 gids.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:22 pm
by ALLWATZ
Stoaty wrote:
edatoakrun wrote: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.
I'm not sure you can make that assumtion although I like the train of thought. All of the cars on the graph are cars experiencing high heat factors anyways, aren't they? I may be wrong but it seems the only way to factor out the heat, for uncorrupted data, is to have cycling data from cars in moderate climate areas to compare with those that we already have. Otherwise the data only shows that it is a spiral effect of high temps=capacity loss=cycling=capacity loss/miles.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:23 pm
by EricBayArea
Adrian wrote:Received an attorney advertisement in the mail today ... http://www.nissanleafproblems.com" onclick="window.open(this.href);return false; ...
I hope to not lose a bar for many years, but if anyone does contact them they might want to point out their poor choice in wording:
Nissan LEAF problems website wrote:...As a result, the vehicle may lose power more quickly and require more frequent charges...
Technically "power" is not being lost, "capacity" is being lost more quickly requiring more frequent charges. Power is what is warranted in the battery warranty, not capacity.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:30 pm
by Herm
Adrian wrote:I know I said in my previous post I drive 80 MPH, but thinking about it, that's not really accurate.
Adrian, what is your lifetime efficiency with the Leaf?, that should describe how you drive.. but I think the important factors at this early loss is how long the battery remains at a high state of charge and at what temperature, not how you drive it.

Re: Early Capacity Losses-Was(Lost a bar...down to 11)

Posted: Fri Aug 17, 2012 1:31 pm
by Stoaty
DarkDave wrote:Count me as another low-mileage 2 bars lost owner. I lost my 2nd bar last week at ~9950 miles. It was almost two months after loosing my 1st bar on 6/15. I've had my Leaf now for almost 18 months.
Looks like you are right on schedule (52.7 days average time between first and second bar loss). Sorry to hear it. Have you filed a case with Nissan? If not, recommend you do so. If you have, can you post the case number and date you filed for the Wiki?

Thanks.