Capacity Loss on 2011-2012 LEAFs

[EdmondLeaf]

has anyone in Phoenix kept their pack below 80% on a regular basis? Just because we are seeing premature capacity loss from folks in the 80% and 100% club I don't think we should assume that charging habits make no difference. It would be very interesting to get the stats on someone who does not plug in every day or otherwise keeps the pack closer to 50% and does things like using an end timer. **IF** the cladding activity curve (assuming that is what is causing this deterioration) is something like exponential at some interval over 50% and multiplied additionally by high spike or average temp, then it would reason that cycling the battery closer to 50% could improve things substantially, presuming these Li cells follow a similar curve to others that have been tested.

I think we know answer to this and it will be NO. Why? Most people charge at home and drive to work, so while they at work during heat hours they already at half or somewhere around 50% of what they started with. If I know how much it takes to drive to place that I have driven so many times, I do not have any reason to top of. Only few have access to evse at work, but even if I will have a possibility to charge at work I will not do it. Maybe I am wrong but according to Nissan 80% is long life mode, but I will be very happy to hear from Nissan on that, in fact I ask this question few times on official Nissan Leaf blog, but looks like Nissan position about long life mode did not change.

Long life mode
NISSAN recommends charging the Li-ion battery using the long life mode to help maximize the Li-ion battery useful life. Long life mode can only be set using the charging timer function.
The long life mode is set by changing the [% Charge] to [80% Charge (Improves Battery Longevity)] using the following procedure.

 

[davewill]

... I would imagine that most LEAF owners in particularly hot areas have central air conditioning. One option would be to insulate the garage as well as possible (note tbleakne's insulated garage door), then add an A/C duct to the garage. ...

If you do that, you'd have to add an air return as well, which is going to possibly vent exhaust gases into your house (unless the LEAF is your only car). The heat-pump hot water heater, or a simple exhaust fan on a timer sounds like a better idea.

 

[Volusiano]

I'm one of the original 5 or 6 in Phoenix who reported losing 1 capacity bar. I finally managed to take my Leaf in to the dealer today for the 1 year battery inspection. It came back with 5 out of 5 stars scores for all 4 categories.

I asked the service advisor about the 1 bar capacity loss and he had an answer for me right away. He told me it's normal to lose 10% of the battery capacity in the first year but the loss should not be linear and in subsequent years, the loss will be much less. I guess Nissan had prepared the dealerships on how to answer this question already, heh?

Also, on my battery report, it shows 11 bars capacity with the following comment: "Gradual loss of capacity is a normal battery characteristic as experienced with cell phones and laptops. The degree of capacity loss will vary based on driving, charging habits, and environmental conditions. This status is also shown on the high voltage battery status meter in instrument cluster (Surrounded by dotted line at the left illustration).

 

[RegGuheert]

Thanks for the update, Volusiano!

I asked the service advisor about the 1 bar capacity loss and he had an answer for me right away. He told me it's normal to lose 10% of the battery capacity in the first year but the loss should not be linear and in subsequent years, the loss will be much less. I guess Nissan had prepared the dealerships on how to answer this question already, heh?

I believe I would have then pushed him by stating "Since it is normal to lose 10% in the first year, then are you saying it is abnormal to lose the 15% that my car has lost?"

But that's just me...

 

[Stoaty]

I asked the service advisor about the 1 bar capacity loss and he had an answer for me right away. He told me it's normal to lose 10% of the battery capacity in the first year but the loss should not be linear and in subsequent years, the loss will be much less.

Did you ask him if he is informing prospective buyers of this fact? If Nissan knows this to be the case they should be telling buyers in hotter places before the sale.

 

[thankyouOB]

anybody here have a thought on whether repair of a Leaf in a painting oven, where the temperature is kept at 100 degrees would be an issue for the battery?

 

[shrink]

I asked the service advisor about the 1 bar capacity loss and he had an answer for me right away. He told me it's normal to lose 10% of the battery capacity in the first year but the loss should not be linear and in subsequent years, the loss will be much less.

Did you ask him if he is informing prospective buyers of this fact? If Nissan knows this to be the case they should be telling buyers in hotter places before the sale.

Wow. I'm in Phoenix and My LEAF is 10 months, 10,000 miles old. I still have all 12 bars, but it doesn't sound like I'm going to have all 12 much longer. I was really hoping these would be isolated incidents, but the data does not look good.

If 10% is normal, isn't 15% the first bar? Is that still normal?

I am seriously regretting buying rather than leasing.

 

[Volusiano]

I did notice that he said 10% while I read elsewhere that the first bar loss is actually 15%. But I wasn't about to nitpick and argue the point with him because it could either be him or Nissan padding down that number to make it look less scary to customers. Besides, if Nissan hasn't been forthcoming with people about the initial first year significant loss of capacity because they want to withhold information until the cat comes out of the bag, or because they didn't know better (their accelerated testing didn't reveal this), then they already lost credibility in what they don't say or don't know, so what's the point of arguing?

The interesting part is that he (representing Nissan) claims that the first year loss won't happen as badly again in subsequent years. How do they know this unless they have data that show this in their accelerated tests? And if they have this data, it also implies that they must know about the first year loss, but chose not to tell people up front.

Another interesting thing the service rep told me is that "Hey, you got nothing to worry about because your battery is warrantied until 100K miles anyway". There's so much fudge about this statement that I didn't want to bother arguing with him either. We already know that Mark Perry clarified that the battery is only warrantied for "power" loss, not for "capacity" loss.

By the way, they did try to hit me up with an air filter cabin change for about $70, brake fluid change for about $130 (?), but I declined both. Also, they pointed out that 2 of my tires were worn out badly on the sides and offered tire replacement and alignment (I'm only at 17.5K miles). I also declined and took my car to Costco afterward for a new set of Michelin Primacy MVX4 instead. Had my alignment done at Brake Plus next and it looked like my front toes were off, which may explain the tire balding.

 

[GaslessInSeattle]

If the average leaf owner is driving 30 miles a day and charging to 100% (the average in the EV project) then it seems the tendency is to overcharge substantially beyond what one needs. For those actually doing long commutes daily there is not much to change accept maybe the time the charge ends and not leaving the car at a low SOC at the end of the day. I hate to say it but if 10-15% loss is being seen in both 100% charging and 80% charging, I don't see what is so "long life" about 80% in hot climates and I would not rely on Nissan to tell us what they really know.

If anyone in a hot climate has been doing shallow cycles closer to the middle SOC, it would be very interesting to know how their pack is holding up.

has anyone in Phoenix kept their pack below 80% on a regular basis? Just because we are seeing premature capacity loss from folks in the 80% and 100% club I don't think we should assume that charging habits make no difference. It would be very interesting to get the stats on someone who does not plug in every day or otherwise keeps the pack closer to 50% and does things like using an end timer. **IF** the cladding activity curve (assuming that is what is causing this deterioration) is something like exponential at some interval over 50% and multiplied additionally by high spike or average temp, then it would reason that cycling the battery closer to 50% could improve things substantially, presuming these Li cells follow a similar curve to others that have been tested.

I think we know answer to this and it will be NO. Why? Most people charge at home and drive to work, so while they at work during heat hours they already at half or somewhere around 50% of what they started with. If I know how much it takes to drive to place that I have driven so many times, I do not have any reason to top of. Only few have access to evse at work, but even if I will have a possibility to charge at work I will not do it. Maybe I am wrong but according to Nissan 80% is long life mode, but I will be very happy to hear from Nissan on that, in fact I ask this question few times on official Nissan Leaf blog, but looks like Nissan position about long life mode did not change.

Long life mode
NISSAN recommends charging the Li-ion battery using the long life mode to help maximize the Li-ion battery useful life. Long life mode can only be set using the charging timer function.
The long life mode is set by changing the [% Charge] to [80% Charge (Improves Battery Longevity)] using the following procedure.

 

[surfingslovak]

If anyone in a hot climate has been doing shallow cycles closer to the middle SOC, it would be very interesting to know how their pack is holding up.

Indeed. The only person I would be aware of is Stoaty. From what I understand, the does not live in a hot climate, but it can get quite warm at his workplace, where the Leaf is parked in an unshaded spot. Judging from the Gid readings he posted on the forum, his battery is doing quite well. Unfortunately, it's only one data point, and not necessarily a good locale to target.

 

[abasile]

... I would imagine that most LEAF owners in particularly hot areas have central air conditioning. One option would be to insulate the garage as well as possible (note tbleakne's insulated garage door), then add an A/C duct to the garage. ...

If you do that, you'd have to add an air return as well, which is going to possibly vent exhaust gases into your house (unless the LEAF is your only car). The heat-pump hot water heater, or a simple exhaust fan on a timer sounds like a better idea.

True enough. Another source of exhaust gases could be a regular, natural gas water heater in the garage. Running a central A/C duct to the garage won't make sense for everyone. A separate wall A/C unit could be another option.

 

[Stoaty]

Indeed. The only person I would be aware of is Stoaty. From what I understand, the does not live in a hot climate, but it can get quite warm at his workplace, where the Leaf is parked in an unshaded spot. Judging from the Gid readings he posted on the forum, his battery is doing quite well. Unfortunately, it's only one data point, and not necessarily a good locale to target.

Yes, not really a good comparison. My Leaf spends about 38 hours a week in the San Fernando Valley in the sun. Of course, that is only a hot spot for about 4 months of the year. I see 6 temp bars routinely in the summer sun, but goes back to 5 bars sometime during the night. I have never seen 7 bars. The rest of the time the Leaf is relaxing in temperatures that are routinely 20-30 degrees cooler than the valley, and stays at 5 bars. I figure the Leaf is exposed to higher temperatures about 25% of the time during 33% of the year, for a total exposure to significant heat of around 8% of the year.

 

[TonyWilliams]

I'm probably over 10%, and I estimate 13% actual performance reduction. The only significant "abuse" is dinging the Turtle about 20 times. I don't work in a "valley" or any other hot spot, and it doesn't stay at 100% charged for any significant time.

 

[GaslessInSeattle]

Yeah, back with the 80% club thread there I remember only 1 or 2 who were applying ultra conservative battery management techniques, which I balked at at the time. with anecdotal evidence of my own, I am seeing extraordinary longevity in a variety of consumer electronics by not leaving them plugged in, shallow cycling, storing at half full and mostly charging just before use. I have one of the first i-phones, purchased in Nov of 2007 and the battery is still going strong... my wife, who has paid no attention to habits, leaving the phone plugged in over night, running it down to dead many times etc, has gone through 3 i-phones in that time. With my MacBook I cycle between 30-80% all day (plugging and unpluging), and after 2 years it's still going strong. My conclusion for now is that the Leaf battery should be treated as any other Li battery, avoiding high SOC and heat, and especially both combined. I now wish the end charging limit could be user defined, allowed for 50% charge initially and an end timer for top up.

I suspect that future BMS's will offer a "commuter mode" that averages out the daily commute needs, cycling around 50%, being extra conservative during times of peak heat and have an over ride for "extended range mode" which fully charges and tops up/balances the cells for long distance travel and TMS.

If anyone in a hot climate has been doing shallow cycles closer to the middle SOC, it would be very interesting to know how their pack is holding up.

Indeed. The only person I would be aware of is Stoaty. From what I understand, the does not live in a hot climate, but it can get quite warm at his workplace, where the Leaf is parked in an unshaded spot. Judging from the Gid readings he posted on the forum, his battery is doing quite well. Unfortunately, it's only one data point, and not necessarily a good locale to target.

 

[opossum]

That's funny. Our Leaf eats 7 temperature bars for breakfast!

Anyway...

Word today is that there's a car here right now at one of the Phoenix dealers that lost a second capacity bar. It's not our (drea / opossum, #0500) car, but I predict we will also join the 2-bar club very soon... unfortunately!

 

[tbleakne]

If anyone in a hot climate has been doing shallow cycles closer to the middle SOC, it would be very interesting to know how their pack is holding up.

Indeed. The only person I would be aware of is Stoaty. From what I understand, the does not live in a hot climate, but it can get quite warm at his workplace, where the Leaf is parked in an unshaded spot. Judging from the Gid readings he posted on the forum, his battery is doing quite well. Unfortunately, it's only one data point, and not necessarily a good locale to target.

All Spring I have been following a regime of charging to mostly 80%, but charging to 90% once a week or so, when I felt I needed more margin for a particular outing, to see if avoiding 100% helped. Now, facing both the onset of warmer weather and a gid loss for 100% charge of 5%, I am now joining the shallow cycle crowd.

Over the last two weeks I have only charged to 80% twice, and once to 89% for the LEAF meeting in Cerritos. As the temperatures warm further I will find out whether this strategy appears to slow further loss, which, if it continues, could seriously impact my driving.

The NREL report states that the shelf-life loss mechanism is well-understood, with a t^(1/2) dependence. It is interesting that the capacity bar size apparently has been chosen to follow this curve, with the first bar largest. The only discrepancy is that the gid readings have NOT been following this curve, having suddenly started dropping just in the last two months for those of us who have had the gid meter since the end of last summer. There has been some speculation that some early loss was hidden from the gids, but unfortunately no one seems to have been regularly taking voltage data at 100% charge with the gid meter, which would have shed light on that possibility.

It seems a lot of folks are focusing on shelf-life loss as the dominant factor, but the NREL study said cycle loss was also important, but it is less well-understood. It is believed to have a linear dependence, but it may not even be predictable.

The loss process at simultaneous high charge and high temperature is well-documented. If the car is parked in this condition regularly, one could call that amplified shelf-life loss. For most folks, however, 100% charges happen most frequently when they are planning to drive further, so stress on the battery is correlated to miles driven.

Extended lifetime with shallow cycling has been well documented for standard Li-Co batteries used in lap-tops, cameras, and cell phones. I am not aware of similar data for our Li-Mn chemistry, but I would expect that shallow cycling would also help us. I could well be wrong.

The data we have collected in Southern California does not seem totally consistent, but it is a small data set and there are a lot of possible factors: day temperature, night temperature, depth of discharge, frequency of high charge, total miles driven, etc. Unfortunately the only folks with all the data is Nissan, and so far they are not talking.

 

[surfingslovak]

Extended lifetime with shallow cycling has been well documented for standard Li-Co batteries used in lap-tops, cameras, and cell phones. I am not aware of similar data for our Li-Mn chemistry, but I would expect that shallow cycling would also help us. I could well be wrong.

The data we have collected in Southern California does not seem totally consistent, but it is a small data set and there are a lot of possible factors: day temperature, night temperature, depth of discharge, frequency of high charge, total miles driven, etc. Unfortunately the only folks with all the data is Nissan, and so far they are not talking.

Very well said Tom, and I share your opinion. This pretty much sums up where we are. Couple of things.

Shallow cycling does apply to LnMnO4 cells, and its benefits have been demonstrated. I posted the results from a paper on generic commercially available lithium-manganese cells a while ago. Note that the green-colored cycle would correspond to approximately LBW to eight bars on the Leaf.

You are correct when you say that large cycling losses have not been observed in the Leaf community, and everything seems to suggest that they are being drowned out by calendar life losses. There is an outlier that seems to prove this point: Steve Marsh. He lives in a cool climate, which should help modulate calendar life degradation, and his high mileage would amplify cycling losses.

Although I believe that Gids have only limited usefulness as a degradation proxy, Steve's battery pack seems to be within 3% of nominal. This would suggest 0.5% loss per 10K miles, possibly even a smaller value. As I mentioned in an earlier post to you, I did some statistical analysis on the data I collected on the forum. Although it's a small sample, and I would not feel comfortable sharing more details, my findings confirm what you said above.

 

[Stoaty]

Word today is that there's a car here right now at one of the Phoenix dealers that lost a second capacity bar. It's not our (drea / opossum, #0500) car, but I predict we will also join the 2-bar club very soon... unfortunately!

That sounds like bad news for the Phoenix folks and others in very hot environments! Keep us posted with more info if available.

 

[kmp647]

I think what is interesting is that Nissan chose to have a capacity gauge at all, and put it in such a prominent place in the instrument cluster.

Does any other lectric car have such a gauge?

I think its says alot about Nissan. Is very forward honest and upfront to provide current and future owners a simple way to judge remaining battery life.

 

[mkjayakumar]

Or Nissan didn't expect such a level of degradation on hot areas in a short amount of time..