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Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 1:41 pm
by leafkabob
Apparently someone in California has dropped a bar also.

http://www.plugincars.com/replacing-ev- ... 22261.html

From the article:
Some owners have already put 30,000 to 40,000 miles on their LEAFs, and we’re getting the first reports of battery power loss. The LEAF has a 12-bar indicator and Nissan says it’s seen the loss of a bar in “a few cases.” Mike Ferry, the transportation programs manager at the California Center for Sustainable Energy, says he’s seen it in exactly one LEAF (with 40,000 miles on it).

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 2:43 pm
by shrink
Well, not that this is a surprise, but Nissan service says the loss is "normal," and I got 5/5 stars on the battery report (although I don't think that's showing up in the scan, but it is indeed 5/5 on all measures). So I'm doing everything they tell me to do in order to take care of my battery, and we lose 15% in the first 10-1/2 months.

I showed the tech the information about lost capacity in the service manual and the expected 20% remaining capacity after 5 years in the disclosure statement. He shook his head and said his information says this is normal. He added that he's seen a lot of cars coming in like that. He also commented, "You can call Nissan," but he again indicated this rate of loss is considered "normal."

Note that even in the Battery Information Sheet, it indicates the car is down to 11 bars (I added the arrow).

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Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 3:28 pm
by Stoaty
Here's another data point for what I would consider "normal" aging of the battery pack:

Code: Select all

Date	  100% Charge	Differential 	Differential Annual	Cumulative Loss 	Cumulative Annual	Comments
	          Percent	        Loss	           Loss Rate		                        Loss Rate

06/12/11	100.0%					                                                                    Assumed, not measured
10/15/11	96.8%	            3.2%	                9.4%              3.2%	              9.4%	Date approximate, Gid meter installed
02/15/12	95.7%	            1.1%	                3.2%              4.3%	              6.3%	Date approximate, battery balanced
06/22/12	94.7%	            1.1%	                3.0%              5.3%	              5.2%	Battery not balanced
Notes:

1) My Leaf spends about 8% of its life in the San Fernando valley when it is hot, the rest of the time it is in parking garage with temperatures between 50 and 75 degrees. (Edit: actually, it also spends another 16% of its life in San Fernando Valley in cooler weather with 5 temperature bars always showing)
2) I don't know if my Leaf suffered a more rapid loss the first 4 months (? from hot summer weather or steeper part of loss curve), or if I never had 281 Gids (meter purchased after 4 months ownership)
3) While the battery might show a few more Gids if balanced, two balancings in a row in February had no effect on the Gid count at 100% charge
4) Differential loss is the loss from one measuring date to the next
5) Annual loss rates were calculated by extrapolation, e.g., a 2% loss over 4 months would be a 6% annual loss rate
6) The annual loss rate is slowing, but factors such as assumed Gid charge when new and hot weather during first measuring period make this questionable without another year of data

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 6:35 pm
by tbleakne
Stoaty wrote:
JPWhite wrote:I see you have 7 temp bars, I've had 6 or less all year. Only saw 7 temp bars once last year after driving fast in heat and charging soon after.
I think that 7 temperature bars (= 98.2 degree F. or above) means that your Leaf has a fever. If the fever persists or goes higher, your Leaf is going to have some degree of brain (battery pack) damage. I have never seen 7 bars on my Leaf, it is usually at 5 bars, but spends significant time at 6 bars in the Valley during the summer; my pack appears to be in good shape (around 95-96% on a full charge by Gid-o-meter last I checked). I propose that time spent at 7 bars or above may be a good indication of who is going to have premature aging of the pack (assuming Leaf is not left at high SOC for significant periods of time). This fits well with the information on the Volt chemistry that 90 degrees is a lot worse for the pack (5 year life expectancy if) than 72 degrees (8 year life expectancy). My guess is that higher spikes are even worse, even if few and short-lived.
I agree with this.
My experience is only slightly worse:
7 bars - once after QC.
6 bars common during the day in both spring and summer.
5 bars almost always by morning from night-time garage temperatures in low 60s.
Currently showing a Gid loss of about 5.5% at 100% charge (based upon recent 80% charges).

However I seem somewhat more concerned about gradual loss than you, because I am not confident that the rate of loss is going to slow down before Fall.

I would suggest one additional rule-of-thumb for modest rate of capacity loss: how much time the car spends at 5 bars. Even though right now, before the worse summer heat, the pack returns to 5 bars at night, I suspect my car spends much less time at 5 bars than yours in your coastal home climate.

Of course time at 4 bars each day would be even better.

If above rule proves out, my loss rate may accelerate somewhat when the battery pack rarely gets back to 5 bars (72 F reported).

I have another basic concern that may well have been voiced by others. As the pack capacity shrinks, I will need to charge closer to the "new" 100% more often to do the same trips without charge in-route. This additional stress will tend to cancel the decline in the t^.5 loss rate.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 7:08 pm
by Stoaty
tbleakne wrote:However I seem somewhat more concerned about gradual loss than you, because I am not confident that the rate of loss is going to slow down before Fall.
Yes, but I am looking at it from a full year perspective. Since I had 5.3% loss the first year I figure worst case for me is 75% loss at 5 years. If loss is steeper at the beginning as Nissan claims, I should be able to retain 80% capacity at 5 years. As you said, my car spends more time at cooler temperature since I live 4 miles from the coast.
I would suggest one additional rule-of-thumb for modest rate of capacity loss: how much time the car spends at 5 bars.
Agreed. This is a good rule of thumb:

7 bars - very bad
6 bars - slightly bad
5 bars - good
4 bars - best (from a capacity loss perspective)
Of course time at 4 bars each day would be even better.
I keep thinking of Abasile and how well his pack is doing. Those cool mountain temperatures don't seem to be hurting his pack any.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 7:36 pm
by smkettner
Not sure I agree 6 bars is slightly bad. Trouble is the range is so great for #6. If you are bouncing 6-7 then I would count it as much worse than bouncing 5-6.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Fri Jun 22, 2012 8:20 pm
by linkim
I just came across an article by John Gartner (Senior Analyst at PIke Research) that summarizes some data (from EERE/DOE and national lab research) on the issue of thermal management of Li-ion batteries and the role on battery capacity.

http://www.plugincars.com/lithium-ion-b ... 22447.html" onclick="window.open(this.href);return false;

To quote: “As the accompanying EERE graphic shows, batteries exposed to hotter average temperatures lose their ability to store energy; the hotter the temperature the faster they lose their storing ability. So BEV owners in Phoenix will likely be looking to replace their batteries faster than owners living where the thermometer doesn’t often reach 110°F.”

There isn’t much specifics on battery chemistry, but the results are from research conducted by NREL, and based on NCA/graphite (Dow-Kokam is mentioned in one presentation I saw) . Furthermore, the results were not obtained with a battery pack not necessarily under operating conditions in real life, and are directed at PHEV technology. Nevertheless, the trend of the results are not very surprising with respect to the geographic location and temperature on loss of battery capacity as a function of time. The data suggests that with no cooling, the Li-ion battery capacity will decrease to 80% in 5 years in Phoenix.

These results may not be comparing apples-to-apples because of battery chemistry, testing protocol, etc. with the LEAF battery capacity fade, but adds to the observations some owners are reporting on the effect of temperature on battery capacity fade. Stay tuned.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Sat Jun 23, 2012 12:38 am
by LEAFfan
linkim wrote:The data suggests that with no cooling, the Li-ion battery capacity will decrease to 80% in 5 years in Phoenix.
It doesn't sound like valid data to me when there are at least 2 LEAFs here that are already less than 80% and many more will likely be less than 80% before summer ends.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Sat Jun 23, 2012 6:43 am
by GaslessInSeattle
tomorrow we begin the relay of Tony's car back to CA. It's quietly resting in my garage right now. There should be some very interesting data from all the continuous quick charging up and down WA and OR. I would be very surprised if the short term temperature spikes of quick charging come anywhere close to being as damaging as continuous high ambient temps.

Re: Lost a "high-voltage battery status" bar, down to 11

Posted: Sat Jun 23, 2012 6:59 am
by EdmondLeaf
I agree, in what is described as hot climate battery have no rest at all without TMS or any active method of cooling battery. I am not driving car for a week already, and I am able to keep car battery in the range of 73 -79F (5 - 6 TB border) while temp outside is: high 95 and low 72F. We have heat dome building so real heat will start this week. The highest battery temp was 89F so far and was very consistent with outside temp while car in the shade all time. My shallow battery temp cycling in garage have about 6 h delay and lowest battery temp is around noon.
I can do experiment like that, it will be for 4 mo, because of carpooling and I have normal car to use. My friend Leaf is only car so will be interesting to see results at the end of summer. Bad part I won't be using cheap energy rate that we have during summer, but expect that less battery degradation will be much much grater value than savings on electric bill.