How should Nissan respond to dropping capacity?

Volusiano said:

Then they went on public with the GreenCarReports article and downplayed it like it was just a fluke/anomaly. If that's the case, why wouldn't they be interested to investigate my fluky case further? That's because they already know. And they TOLD ME that THEY KNOW.

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I agree with most everything said in this thread and that there appears to be a real problem with heat but the greencareports article is useless as a reference. It is by no means a statement from Nissan. It is an unknown person who claims to be a Nissan employee who made a statement at an unknown point in time.

Nissans silence is not good. They need to make some sort of statement soon even if it is just to say "we are aware and are investigating"

I feel a need to provide at least 1 data point showing that not all Phoenix Leafs are losing significant battery capacity: After 12 months and 11,400 miles, I still have 12 bars and, as far as I can tell, have not lost significant capacity. Since I do not have a Gid meter, my method to keep track of battery capacity has been to record charging energy. I have recorded charging energy from shutdown to 100% several times over the past year and have not seen a significant decrease. My capacity may have started out a bit lower than others have reported, but it has dropped very little over the past year. I need to get the data entered into a suitable spreadsheet to post. I have done things that may be bad for the battery and other things that should be good:

1. Almost every charge is to 100%, but I never initiate a charge unless I have discharged the battery enough to accept full regeneration. I only recharge above 50% SOC if I need the range for a particular trip. I am usually down near LBW or VLBW before I charge. Almost all charging is off peak (at night) at home. I used QC once in December.

2. My round trip commute is 52 miles, mostly freeway with surface streets at each end and I always keep up with traffic in the HOV lane. I typically add a few miles of errands on surface streets. I also frequently use all 80 kW accelerating from stop lights.

3. The car is parked on concrete under covered parking either at my office or the airport. At home, it is either on the concrete driveway (in the shade of a tree during late afternoon) or in the garage.

4. Based on the bar graph (fuel gauge) and typical range, I am guessing that the car is at 60-65% SOC whenever it is parked for an extended period of time at the office or airport.

5. Over the past year, my battery temperature has ranged between 4 and 8 bars. Lately, it has been 6 after cooling overnight and 7 during the day. It spent a significant amount of time at 8 during the hottest part of last summer.

I may be the only Leaf owner in Phoenix who feels this way, but I am glad that Nissan chose not to use active battery cooling. As a field engineer, I like the "keep it simple" approach. Also, I would not want to return to the car to find a dead (or partially depleted) battery because the cooling system tried to keep it cool while I was gone.

I have been waiting for the LeafSCAN to become available, but am now thinking about ordering a Gid meter kit in the meantime to get something to monitor my battery.

Gerry

I have a GID meter and would be willing to arrange to take a reading after a 100% charge, for those in the Chandler/Tempe/Phoenix area. Please send me a PM if you're interested and we can work out a time.

GerryAZ said:

I have recorded charging energy from shutdown to 100% several times over the past year and have not seen a significant decrease.

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This is really the best way to measure capacity - a discharge/range test and a charge test (measure full charge energy). It could be more reliable than the GID as the GID is likely compensated by some unknown factors.

A discharge test would be done over a known loop which is easy to repeat and preferably done down to at least VLBW if not turtle. Before the test, charge to 100% - I would suggest charging to 100% on L1 which should give the car more time to balance cells. Record miles traveled and dash reported economy at LBW, VLBW and turtle. I also recommend recording L1 time to 100% (Better (reverse) SOC meter already in the car?)

A charge test would drain the battery to LBW, VLBW or turtle and then record the amount of energy it takes to charge back up to 100%. Blinks can record this data - I would hesitate to recommend a Kill-A-Watt because it's been known to melt under L1 loads along with the time it would take to charge from turtle to 100%. It would be nice to have a meter that easily plugged in between a EVSE upgrade or other L2 - but this would likely cost at least $100 to build, so the Blink appears to be the best option here for those who have it.

GerryAZ said:

I may be the only Leaf owner in Phoenix who feels this way, but I am glad that Nissan chose not to use active battery cooling. As a field engineer, I like the "keep it simple" approach. Also, I would not want to return to the car to find a dead (or partially depleted) battery because the cooling system tried to keep it cool while I was gone.

I have been waiting for the LeafSCAN to become available, but am now thinking about ordering a Gid meter kit in the meantime to get something to monitor my battery.
Gerry

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Thanks for the input, Gerry. I still have all 12 capacity bars, too, but there's definitely some loss of range. LEAFfan's ScanGuage read 85.7% on my car about a month ago after a 100% charge. I'm sure he'd be willing to take a reading on your car as well if you're interested.

I couldn't disagree with you more about the battery cooling, or in Volt lingo, thermal management system (TMS). I'll link to a very interesting post about the Volt's TMS. A few highlights:

1)Your battery would never be fully depleted due to active cooling. It won't run if not plugged in with a SOC less than 75%.

2) Quoted from the linked post:

"there is a substantial lifetime difference between 21C (70F) and 32C (90F) in the lithium-manganese batteries (which have the highest heat sensitivity/degradation profile of all lithium battery chemistries) that GM is using in the Volt. At 60% SOC, lithium-manganese batteries have a little over 8 year life at 21C (70F) but only a 5 year life at 32C (90F). At higher states of charge, the heat sensitivity and degradation rate is even greater."

3) The insulation of the TMS alone will slow heat conduction to some degree.

Here's the full link:

http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=45948#post45948" onclick="window.open(this.href);return false;

Anyway, glad to hear you haven't noticed any loss of capacity, but please do keep us posted.

GerryAZ said:

I feel a need to provide at least 1 data point showing that not all Phoenix Leafs are losing significant battery capacity: After 12 months and 11,400 miles, I still have 12 bars and, as far as I can tell, have not lost significant capacity. Since I do not have a Gid meter, my method to keep track of battery capacity has been to record charging energy. I have recorded charging energy from shutdown to 100% several times over the past year and have not seen a significant decrease. My capacity may have started out a bit lower than others have reported, but it has dropped very little over the past year. I need to get the data entered into a suitable spreadsheet to post.

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Thanks for the encouraging report, Gerry! I think the data you have is quite unique since it sounds like it covers the entire 12 months since you received the car. I look forward to seeing more details!

shrink said:

At 60% SOC, lithium-manganese batteries have a little over 8 year life at 21C (70F) but only a 5 year life at 32C (90F). At higher states of charge, the heat sensitivity and degradation rate is even greater."

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Since the average temperature in Phoenix is 82° F then that battery will last a bit more than 5 years. More if Nissan tweaked the electrolyte.

But there are 3 months with average temperatures higher than 90ºF (July the hottest with 95ºF average temperature), and the pack probably experiences higher average temperatures than the ambient temperature because of the heat generated during charging and driving. As the degradation is non linearly accelerated with these higher temperatures, they probably experience (much) more degradation than a pack with an average temperature of 82ºF. It is the same principle that driving at a fixed speed of 90 km/h consumes less energy than driving half the trip at 120km/ and the rest at 60km/h (90 km/h average).

And I believe last summer the temperatures where way above the average...

GerryAZ said:

I feel a need to provide at least 1 data point showing that not all Phoenix Leafs are losing significant battery capacity: After 12 months and 11,400 miles, I still have 12 bars and, as far as I can tell, have not lost significant capacity. Since I do not have a Gid meter, my method to keep track of battery capacity has been to record charging energy. I have recorded charging energy from shutdown to 100% several times over the past year and have not seen a significant decrease. My capacity may have started out a bit lower than others have reported, but it has dropped very little over the past year.

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While this is interesting and somewhat encouraging, the best way we currently have to compare cars is to use the Gid-o-meter on a fully charged and well-balanced battery. Otherwise, there are too many variables that may affect the result. The Gid-o-meter has been a very good predictor of when someone is about to lose a capacity bar.

Herm said:

shrink said:

At 60% SOC, lithium-manganese batteries have a little over 8 year life at 21C (70F) but only a 5 year life at 32C (90F). At higher states of charge, the heat sensitivity and degradation rate is even greater."

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Since the average temperature in Phoenix is 82° F then that battery will last a bit more than 5 years. More if Nissan tweaked the electrolyte.

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but spends over 14 hours a day in summer at 100+ which probably will bring it back under 5 years. wondering what Nissan will do when the first pack hits 70%? by that time, packs from TN should be plentiful

OrientExpress said:

Accelerated vs. Nissans claim of 80% capacity after 5 years.

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And there is nothing so far in any of the concerns expressed in this thread (or any other), other than speculation to suggest otherwise.

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You act as if we have somehow collectively imagined that these cars have lost capacity. We have not imagined anything. Nissan has STATED that the cars with one missing bar have lost 15% of their capacity due to usage or aging. Nissan has STATED that the cars with two missing bars have lost 21.25% of their capacity due to usage or aging.

Here is what the 2011 LEAF Owner's Manual Revised says on page 2-10:

2011 LEAF Owner's Manual Revised said:

LI-ION BATTERY CAPACITY LEVEL GAUGE
This gauge indicates the amount of charge the Li-ion battery is capable of storing.
When the capacity of the Li-ion battery decreases with age and usage, the level of the gauge will also decrease.

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So the question becomes "How much does it decrease?" Nissan provides us with the answer to that question on page MWI-23 of the LEAF Service Manual: Revision Unknown. Please note that this information is NOT in the version of the Service Manual that I have, but assumedly it was in a different version. Here is a link to the Wiki with a chart that apparently came from some version of the 2011 LEAF Service Manual. Can someone please tell us what version that is from?

So, is the Li-ion battery capacity level gauge level a function of temperature? Not according to Nissan. Here is what they say on page MWI-24 of the 2011 Nissan LEAF Service Manual, Revision April 2011:

2011 Nissan LEAF Service Manual: Revision April 2011 said:

Li-ion battery capacity level gauge is immune to temperature change.

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The point is that all of this information came from Nissan and some cars are apparently indicating 2 bars missing.

OTOH, there is also this statement on page EV-3 of the 2011 LEAF Owners's Manual Revised:

2011 LEAF Owners's Manual Revised said:

The capacity of the Li-ion battery in your vehicle to hold a charge will, like all such batteries, decrease with time and usage. As the battery ages and capacity decreases, this will result in a decrease from the vehicle's initial mileage range. This is normal, expected, and not indicative of any defect in your Li-ion battery. NISSAN estimates that battery capacity will be approximately 80% of original capacity after five years, although this is only an estimate, and this percentage may vary (and could be significantly lower) depending on individual vehicle and Li-ion battery usage.

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Emphasis mine. Note that this statement was also in the original manuals that came with our cars.

The point is that the capacity losses are real according to Nissan, but their response is that they are normal. What seems to be missing in all this is that Phoenix owners were never told that they should ALL expect for that bolded section to apply directly to their car. Caveat emptor at its best if you ask me.

RegGuheert:

I think you answered your own question, there is no conspiracy or problem here, it is well known that battery capacity does go down over time, and Nissan as are other manufacturers quite upfront and clear about this.

Would it be nice if everything lasted forever? Of course, but in reality, that is not the case. Is the saying "Your Mileage may vary" valid? Sure it is.

At the end of the day, the LEAFs that are in operation in hot weather (and the others in less harsh environments) all over the world, including Phoenix, continue to operate well, they start up every morning, they take their drivers where they need to go, they don't stall in the middle of the road, and all of their systems continue to operate as advertised and claimed by their manufacturers.

OrientExpress said:

I think you answered your own question, there is no conspiracy or problem here, it is well known that battery capacity does go down over time, and Nissan as are other manufacturers quite upfront and clear about this.

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How much is Nissan paying you for writing this fluff instead of discussing the legitimate problems of those in very hot climates?

1.

I have to side with everyone else on this one. Calling names and making innuendos will not make what appears to be a real and significant issue go away...

OrientExpress said:

How much are the oil companies paying you to demonize EVs?

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DaveinOlyWA said:

Herm said:

Since the average temperature in Phoenix is 82° F then that battery will last a bit more than 5 years. More if Nissan tweaked the electrolyte.

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but spends over 14 hours a day in summer at 100+ which probably will bring it back under 5 years. wondering what Nissan will do when the first pack hits 70%? by that time, packs from TN should be plentiful

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An average is an average, non-linear cell degradation is another issue. It takes a while for the pack temps to go up once the day starts to heat up. Surprised no one has instrumented the battery case to measure the temperature.. I bet outside case temp closely tracks inner cell temps.

http://www.amazon.com/Digital-temperature-meter-remote-sensor/dp/B002B0KVFQ/ref=sr_1_7?ie=UTF8&qid=1340203113&sr=8-7&keywords=temperature+sensor" onclick="window.open(this.href);return false;

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OrientExpress said:

How much are the oil companies paying you to demonize EVs?

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There is a difference between demonizing and pointing out legitimate problems. I strongly support EVs, but I don't owe blind loyalty to a particular manufacturer. The issue here is that Nissan apparently knew about this problem and didn't disclose it. That gives Nissan a bit of a black eye in my opinion. Given the available data, I won't currently recommend anyone who lives in a very hot climate to buy a Nissan Leaf (leasing would be fine). Sticking our heads in the sand isn't going to make this problem go away.

I hope Nissan will step up to the plate the way GM did about a non-issue (Volt battery fire). They offered to buy back a Volt from anyone who was concerned. This strong stance caused the concerns to melt away, and the Volt is doing fine with sales. I don't know exactly what Nissan should do, but I think they ought to put out this "fire" before it goes any further.

The issue here is that Nissan apparently knew about this problem and didn't disclose it.

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Therein lies the disconnect. Diminished Battery capacity over time is a known characteristic of all batteries, not a problem, as in a manufacturing or design problem, which is what is alluded to here.

Nissan and all manufacturers of EVs know that over time the capacity of the batteries that power their cars will diminish, and are quite transparent about communicating that with the general public. As you know almost as much space in the owners manuals is devoted to this issue as how to wear seat belts and use airbags. It is a issue that Nissan goes above and beyond to communicate and explain to the owners of their cars, because it is unique to EVs.

Can anyone predict with absolute confidence how slowly or rapidly that will occur, no, because there are too many environmental variables to factor in.

These are the facts, and that is that.

OrientExpress said:

At the end of the day, the LEAFs that are in operation in hot weather (and the others in less harsh environments) all over the world, including Phoenix, continue to operate well.

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Yeah, they just don't go as far as similarly aged LEAFs in cooler climates. How about we switch cars or battery packs at the end of the summer this year? I only have 10,000 miles on mine. Sounds like a win-win for you.

drees said:

GerryAZ said:

I have recorded charging energy from shutdown to 100% several times over the past year and have not seen a significant decrease.

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This is really the best way to measure capacity - a discharge/range test and a charge test (measure full charge energy). It could be more reliable than the GID as the GID is likely compensated by some unknown factors.

A discharge test would be done over a known loop which is easy to repeat and preferably done down to at least VLBW if not turtle. Before the test, charge to 100%...

A charge test would drain the battery to LBW, VLBW or turtle and then record the amount of energy it takes to charge back up to 100%...

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Or just use Carwings Electricity Consumption kWh use report for the same test loop.

More accurate, IMO, as the recharge will probably not be to exactly the same capacity level.

My own capacity test here:

http://www.mynissanleaf.com/viewtopic.php?f=31&t=9064&p=207152#p207152" onclick="window.open(this.href);return false;