Capacity Loss on 2011-2012 LEAFs

[TonyWilliams]

**The Volt may not be showing similar degradation because of various factors that include a MUCH higher reserve/buffer of unused capacity. GM did this because longevity of the pack was more important that Electric range since the Volt has a gas engine.**

It's done to satisfy emission control and battery warranty requirements that don't apply to a pure electric, like LEAF.

 

[NYLEAF]

Tropics and Deserts are Very different. I haven't heard of many problems with Leaf batteries in Florida, Georgia, and other places in the HOT, but HUMID areas.
The humidity really help moderate the temps, even though humans feel hotter when the humidity is high, equipment seems to hate the dry heat more.

The Leaf wasn't available in Florida and Georgia as early as it was available in California and Arizona. I doubt the humidity is helping the Leafs in Florida. I bet we will see a whole thread of Florida Leafers missing bars come June...

 

[surfingslovak]

I think that active cooling may mitigate the capacity loss somewhat, but it certainly won't be a silver bullet that avoids the calamity we are seeing in Arizona, Texas and SoCal.

Agreed, there is some other factor that makes these cells fade a bit faster. It's been suggested that it could be the particular selection of electrolyte. As to the Volt, you might want to review this thread on their forum, its TMS seems pretty sophisticated. Some posters think the having three cells in parallel instead of two is an advantage as well. And lastly, the pack is insulated, and could stay below ambient for a while even when left unplugged.

 

[Joeviocoe]

So now Nissan is blaming high speed driving for battery capacity loss...I do not use the freeway and drive slow (6.1M/KW) and still loss 2 capacity bars in one month Nissan ..
So lets see what Nissan new rules are for Phx and the Leaf..
1. Do not drive fast,No freeway driving..
2. Do not drive in the heat
3. Do not park in the heat
4. Do not charge in the heat and only 80%
5. Use of Leaf only in the winter time is highy recommended by Nissan

I don't own a Leaf, so I don't know... but please tell me.
Is this OFFICIAL statements from Nissan of North America? Or is this some sale/service rep at one of the dealerships in Arizona?
I know ONLY of the recommendations to only charge up to 80%.
But who is officially recommending those 5 points? Who from Nissan is recommending lower speeds or (as Spooka's video claims) less annual driving????

Got this
Now the results of a Nissan study of those vehicles are in. The cars are being driven too much. According to Green Car Reports, Nissan says:
Average annual mileage [of those cars] is about 16,000 per year, more than double the average Phoenix customer mileage of 7,500 miles per year.
From here
http://www.technologyreview.com/view/429330/dont-drive-your-nissan-leaf-too-much/" onclick="window.open(this.href);return false;
And this
In an official letter to the Leaf community, a Nissan executive ties the complaints to high mileage. The miles from the seven cars tested averaged about 16,000 miles a year. Nissan's owner manual states the one-year checkup for the car is at 15,000 miles. The company now states 7,500 miles a year is the average commute for a Phoenix driver.
From here
http://www.kpho.com/story/19651301/pulling-the-plug-nissan-buys-back-at-least-two-nissan-leafs-under-arizonas-lemon-law" onclick="window.open(this.href);return false;
So Nissan says Phx drivers average 20 miles/day but here
http://green.autoblog.com/2011/10/28/nissan-claims-average-leaf-is-driven-37-miles-per-day-more-rang/" onclick="window.open(this.href);return false;
Nissan states the national average is almost double that of Phx at 37 miles per day. I find that interesting to say the least.

Thank you.
So what I got from the links you provided:
The part about expecting Phoenix drivers to only drive 7,500 miles annually, which is NOT part of the 5 statements listed, is verifiably TRUE.

However, NONE of the 5 points listed by the originally quoted comment... is something that Nissan has officially stated.
*other than the second half of #4 (Nissan does recommend only charging to 80%).

I still don't know where he got those 5 statements... it still looks as though it was just an attempt at humorous supposition.

 

[surfingslovak]

The Leaf is scheduled to be available in Puerto Rico this year and let me tell you, it is hotter than hell down there year round and there is zero infrastructure for electric vehicles at this time. Don't know where the government is gonna get money to do that as they are broke. Traveling down there this Saturday for 2 weeks and will report back on any Leaf sightings. I think this car is not fit for the island of Puerto Rico if the batteries can not take the heat but, we will see.

Ian B

Tropics and Deserts are Very different. I haven't heard of many problems with Leaf batteries in Florida, Georgia, and other places in the HOT, but HUMID areas.
The humidity really help moderate the temps, even though humans feel hotter when the humidity is high, equipment seems to hate the dry heat more.

While that's possible, first Leafs were not delivered in Florida until sometime in November or December last year. I could be wrong, but based on the temperature modeling we did, there is a good chance that we will see first lost bar reports early next year. While we have a sample of one from Hong Kong, I would argue that not many people drove a Leaf there. And it's also quite humid.

 

[Joeviocoe]

Tropics and Deserts are Very different. I haven't heard of many problems with Leaf batteries in Florida, Georgia, and other places in the HOT, but HUMID areas.
The humidity really help moderate the temps, even though humans feel hotter when the humidity is high, equipment seems to hate the dry heat more.

The Leaf wasn't available in Florida and Georgia as early as it was available in California and Arizona. I doubt the humidity is helping the Leafs in Florida. I bet we will see a whole thread of Florida Leafers missing bars come June...

What about the availability in Hawaii? They got Leafs as early as Texas did. And Texas has problems, Hawaii none.

http://www.nissan-global.com/EN/NEWS/2010/_STORY/100727-02-e.html" onclick="window.open(this.href);return false;

Also, Florida missed out on several spring months, but got Leafs during the summer just the same.

The humidity actually lowers the temperature overall. We don't feel it the same, cause we sweat and we measure our own temps by really measuring how fast we get rid of the skin heat. So since the sweat doesn't evaporate, we FEEL hotter in humid climates. While in the desert, we ARE hotter, but feel cooler since evaporation is faster.

The deserts of Arizona, are much hotter than the heat of the tropics.

 

[Joeviocoe]

While that's possible, first Leafs were not delivered in Florida until sometime in November or December last year. I could be wrong, but based on the temperature modeling we did, there is a good chance that we will see first lost bar reports early next year. While we have a sample of one from Hong Kong, I would argue that not many people drove a Leaf there. And it's also quite humid.

Statistically, a single occurrance of a lost bar is irrelevant. There is just as much probability that the Hong Kong leaf has a random problem. And, as you mentioned, the sample size is also too small to conclude that this one Leaf should be considered as part of the overall issue being discussed here.

 

[surfingslovak]

While that's possible, first Leafs were not delivered in Florida until sometime in November or December last year. I could be wrong, but based on the temperature modeling we did, there is a good chance that we will see first lost bar reports early next year. While we have a sample of one from Hong Kong, I would argue that not many people drove a Leaf there. And it's also quite humid.

Statistically, a single occurrance of a lost bar is irrelevant. There is just as much probability that the Hong Kong leaf has a random problem. And, as you mentioned, the sample size is also too small to conclude that this one Leaf should be considered as part of the overall issue being discussed here.

Agreed, please don't start preaching about statistics. I got that is spades earlier this year when I tried to get some people pay attention to this phenomenon, which they dismissed as a rounding error at the time. I noticed that you came here from external blogs. How much do you know about the Leaf? Did you own one?

 

[Joeviocoe]

I think that active cooling may mitigate the capacity loss somewhat, but it certainly won't be a silver bullet that avoids the calamity we are seeing in Arizona, Texas and SoCal.

Agreed, there is some other factor that makes these cells fade a bit faster. It's been suggested that it could be the particular selection of electrolyte. As to the Volt, you might want to review this thread on their forum, its TMS seems pretty sophisticated. Some posters think the having three cells in parallel instead of two is an advantage as well. And lastly, the pack is insulated, and could stay below ambient for a while even when left unplugged.

THANK YOU

I was looking all around for this information.

Although this link, http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band/page13" onclick="window.open(this.href);return false;
does provide a good summary.. Chris C directly references Charles Whalens write up here:
http://gm-volt.com/forum/showthread.php?5243-Volt-thermal-management-system-temperature-band&p=45948#post45948" onclick="window.open(this.href);return false;

"When either a) the car is off and not plugged in, or b) the car is plugged in but not charging (i.e. either prior to commencing a timed/programmed charge or after having completed charging but still plugged in):
If the battery pack is at very high SOC, from 85% SOC (top of the charge and top of the Volt’s usable SOC range) down to around 75% SOC, the car’s electronics will wake up the TMS periodically, around once every half hour, to see if the TMS needs to run. If the battery pack is below about 75% SOC, the TMS never wakes up and never runs."

So if you leave the Volt in the Heat of the Day with over 75% SOC... you're good to go, the TMS WILL actually run even when unplugged and parked.
But the average commute is 12 - 15 miles IIRC... and the 100% SOC refers to 35 miles. So after driving TO WORK, your SOC will be 57% - 66%
So for most cases, the TMS never turns on while most commuters are parked in the sun, despite high temps.
Although I do like the insulation keeping things moderate... I still think that 110F ambient heat during the day for several hours, will put the pack temps well over the limit that requires TMS.

Could the Leaf have a similar TMS??? Nissan recommend only charging to 80% already, so TMS would need to have much lower limits.

I do like the idea of choice, for some Phoenix residence to lose daily range if they are parked in the sun, while keeping the pack healthier in the long run. How much range will be lost by using pack energy to run the TMS in 100F temps...??? that is the million dollar question.

 

[Joeviocoe]

While that's possible, first Leafs were not delivered in Florida until sometime in November or December last year. I could be wrong, but based on the temperature modeling we did, there is a good chance that we will see first lost bar reports early next year. While we have a sample of one from Hong Kong, I would argue that not many people drove a Leaf there. And it's also quite humid.

Statistically, a single occurrance of a lost bar is irrelevant. There is just as much probability that the Hong Kong leaf has a random problem. And, as you mentioned, the sample size is also too small to conclude that this one Leaf should be considered as part of the overall issue being discussed here.

Agreed, please don't start preaching about statistics. I got that is spades earlier this year when I tried to get some people pay attention to this phenomenon, which they dismissed as a rounding error at the time. I noticed that you came here from external blogs. How much do you know about the Leaf? Did you own one?

No, I don't own one. I came from Autoblog Green.
Does that necessarily discount relevant analysis? Not really. I don't need to be an owner to know about the statistics or the engineering. If this were a debate about ride comfort, or dealing with customer service or something only an owner could understand, I wouldn't have much to say.

I'm sorry if people were discounting you earlier this year... but to be honest, there are good engineering reasons for this phenomenon that should not have been overlooked even before the first Leaf reported bar loss. So as the first Leafs reported in, they should not dismiss based on any statistics. Just like Nissan should not be calculating estimated range of typical Phoenix residence as being half the national average. I don't want to come off as dismissive of the Hong Kong Leaf, it certainly needs to be tested and fixed... but advise caution before adding it to the larger data set.

 

[Weatherman]

Until the first Florida LEAF can pass the 20,000 mile or 20 month mark (whichever comes first) and keep all its battery capacity bars, I won’t be waiving the all clear flag for tropical climates, yet.

And, unless your LEAF is unique and relies on evaporative cooling to cool off the battery, humidity is irrelevant. 35C is 35C, no matter where you are.

 

[surfingslovak]

No, I don't own one. I came from Autoblog Green.
Does that necessarily discount relevant analysis? Not really. I don't need to be an owner to know about the statistics or the engineering. If this were a debate about ride comfort, or dealing with customer service or something only an owner could understand, I wouldn't have much to say.

I'm sorry if people were discounting you earlier this year... but to be honest, there are good engineering reasons for this phenomenon that should not have been overlooked even before the first Leaf reported bar loss. So as the first Leafs reported in, they should not dismiss based on any statistics. Just like Nissan should not be calculating estimated range of typical Phoenix residence as being half the national average. I don't want to come off as dismissive of the Hong Kong Leaf, it certainly needs to be tested and fixed... but advise caution before adding it to the larger data set.

Point taken, and you are absolutely right. At the same time, it should be noted that there is plenty of engineering and scientific talent on this board. We've discussed this from several angles, over many months, and there was no shortage of ideas. Sometimes it felt like we were not talking about anything else.

The statements we have heard from Nissan provided some additional insight, but not necessarily closure. Although there is still much to be learned for us engineering types, I don't think that well-meaning advice from a talented blog reader will provide the insight that somehow eluded us all this time. It's possible, but unlikely at this point. I think only Nissan can do us that favor.

Thank you for creating the geomap BTW

Until the first Florida LEAF can pass the 20,000 mile or 20 month mark (whichever comes first) and keep all its battery capacity bars, I won’t be waiving the all clear flag for tropical climates, yet.

And, unless your LEAF is unique and relies on evaporative cooling to cool off the battery, humidity is irrelevant. 35C is 35C, no matter where you are.

That's very interesting! Thanks for the climatic data you provided. Any chance I could fit it in this spreadsheet?

 

[DaveEV]

So for most cases, the TMS never turns on while most commuters are parked in the sun, despite high temps.
Although I do like the insulation keeping things moderate... I still think that 110F ambient heat during the day for several hours, will put the pack temps well over the limit that requires TMS.

Well sure - leaving the car plugged in all day so it can keep the batteries at a very comfortable 75F would be ideal. But take your typical Volt which is driven as a commuter and compare it to the LEAF in Arizona heat.

The Volt pack is cooled to 75F between the time the owner leaves work and they arrive at work. Let's say that's between 6pm - 8am, or over half the day. That does leave the battery to bake for 10 hours during the day, so it's temp is probably getting close to ambient near the end of the day assuming the SOC is low enough (would be nice to have some data from a Phoenix Volt).

In contrast, the LEAF's battery is going never going to get much below 100F. Your typical garage does not cool off much at night. In the summer, Phoenix stays above 90F, so the garage will probably say around 100F through the night. In fact, TickTock plotted this for us: A day in the life of a Phoenician Leaf Battery You can see that the case of his battery is basically at 100F 24 hours a day despite having underground parking. You can see the spike to 110F during the commute home - you know for sure that a car parked in the sun will probably not take more than 3-4 hours to reach that temp since the LEAFs pack is not well insulated.

Knowing that battery degradation basically doubles for every 10C increase in temperature thanks to the Arrhenius Equation, a typical LEAF battery is spending 14 hours/day at temps 15-20C warmer than the Volt battery during the summer. Since the Volt's pack is insulated and will retain the cold for some time, let's simplify for some back of the envelope calcs.

Assume Volt pack is 20C cooler for 12 hours / day - the other 12 they are the same (take that Volt out to lunch to cool the battery off!). So for 12 hours a day, the LEAF battery is aging 4x faster than the Volt's - in other words, assuming that the Volt pack is your baseline - the LEAF pack will age 2.5 times faster than the Volt (and I imagine the actual data is even better than that since the Volt never spends any time at high SOC unless it's cooled).

That's pretty much like living near the coast in California instead of Arizona in terms of rate of capacity loss using my extremely rough back-of-the envelope estimate. In fact, this
Thermal Management Presentation from the SAE and NREL suggests that in a PHEV application, a insulated and liquid cooled pack in Phoenix will age better than a pack with no TMS in Minneapolis.

We certainly would not be having this discussion today if the LEAF were equipped with a TMS system similar to the Volts.

 

[shrink]

The Volt pack is cooled to 75F between the time the owner leaves work and they arrive at work. Let's say that's between 6pm - 8am, or over half the day. That does leave the battery to bake for 10 hours during the day, so it's temp is probably getting close to ambient near the end of the day assuming the SOC is low enough (would be nice to have some data from a Phoenix Volt).

We certainly would not be having this discussion today if the LEAF were equipped with a TMS system similar to the Volts.

Very well said, as usual, drees.

I have a Phoenix Volt, but there is no battery temperature gauge that I know of, so I would have no idea. When I do drive it to work (I typically bike), my commute is so short (less than 2 miles) that the SOC is high enough to keep the TMS periodically running. I have covered parking at work, too. All these factors help - especially during a desert summer with weeks of highs over 110F.

Would another potential benefit of a LEAF TMS possibly be more frequent quick charging? I am no engineer, but couldn't a TMS keep the battery cool and offset the heat generated from a QC? If so, I think this could potentially make the car much more useful - even to those in cooler climates, some of whom don't seem to want a TMS due to added expense. Sometimes an added expense that you may not use often is well worth it. I mean, we all have insurance, and it certainly is not a bad idea to take extra measures to improve the longevity of the most important part of the car.

 

[spike09]

Tropics and Deserts are Very different. I haven't heard of many problems with Leaf batteries in Florida, Georgia, and other places in the HOT, but HUMID areas.
The humidity really help moderate the temps, even though humans feel hotter when the humidity is high, equipment seems to hate the dry heat more.

The Leaf wasn't available in Florida and Georgia as early as it was available in California and Arizona. I doubt the humidity is helping the Leafs in Florida. I bet we will see a whole thread of Florida Leafers missing bars come June...

How much are you willing to wager that my LEAF will still have 12 bars come June 2013? Abnormal battery loss is somewhere between 1% to 10% of the LEAF population. I will take that bet!

 

[DaveEV]

Would another potential benefit of a LEAF TMS possibly be more frequent quick charging? I am no engineer, but couldn't a TMS keep the battery cool and offset the heat generated from a QC? If so, I think this could potentially make the car much more useful - even to those in cooler climates, some of whom don't seem to want a TMS due to added expense.

It definitely would in any climate where you being your QC at 6 temp bars. And we all know that if you want to QC 2-3+ times a day QC-hopping, that will definitely raise the temperature up close to the danger zone. Active cooling may allow you to QC faster as well (delay the tapering seen past 50% SOC so you get to 80% faster).

How much are you willing to wager that my LEAF will still have 12 bars come June 2013? Abrormal battery loss is somewhere around 1 to 10% of the LEAF population. I will take that bet.

I smell a pizza bet coming on...

 

[surfingslovak]

How much are you willing to wager that my LEAF will still have 12 bars come June 2013? Abrormal battery loss is somewhere around 1 to 10% of the LEAF population. I will take that bet.

I smell a pizza bet coming on...

Me too! With the new data from no other than Mr. Weatherman (thank you), it looks like Fr. Lauderdale could be milder, and perhaps comparable to Van Nuys in terms of its climatic impact. With 9,000 annual miles, it could take you almost two years to lose the first bar, if the new weather data is correct. If the old data is correct, then the first bar could go next summer. Any idea where to get accurate climatic data for Miami? For half a pizza? ;-)

 

[spike09]

How much are you willing to wager that my LEAF will still have 12 bars come June 2013? Abrormal battery loss is somewhere around 1 to 10% of the LEAF population. I will take that bet.

I smell a pizza bet coming on...

Me too! With the new data from no other than Mr. Weatherman (thank you), it looks like Fr. Lauderdale is milder, and perhaps comparable to Van Nuys in terms of its climatic impact. How many miles do you average per month?

I average 25 miles a day and live near the coast (not close enough to hear the surf or afford a Tesla!) which is at least 10 degrees cooler than living inland where ocean cooling has no effect.

 

[Joeviocoe]

Until the first Florida LEAF can pass the 20,000 mile or 20 month mark (whichever comes first) and keep all its battery capacity bars, I won’t be waiving the all clear flag for tropical climates, yet.

And, unless your LEAF is unique and relies on evaporative cooling to cool off the battery, humidity is irrelevant. 35C is 35C, no matter where you are.

"35C is 35C, no matter where you are." Absolutely... but that is as hot as Florida normal stays during the summer (with the occasional exception). Arizona gets past 40C... and is much more consistent. Humidity does drive down the overall climate. When people say Florida gets just as hot, they are talking about how hot it FEELS...

That is why, when people from Florida visit family in Vegas or Arizona, they say, "it's hotter, but it's a dry heat".... meaning that it Feels cooler than it actually is.

My point was exactly that Batteries don't feel any real effects from humidity. And thus, won't experience as much heat as people might think in Florida.
But I too, "..won’t be waiving the all clear flag for tropical climates, yet". There needs to be more time and data collected before we know.

Has any Hawaii Leafs passed the 20k mile or 20 month mark????

 

[surfingslovak]

I average 25 miles a day and live near the coast (not close enough to hear the surf or afford a Tesla!) which is at least 10 degrees cooler than inland where ocean cooling has no effect.

Nice! Sounds like you will be fine then.

Has any Hawaii Leafs passed the 20k mile or 20 month mark????

We don't know. But it looks like the Leaf owner in Hong Kong is averaging 1,700 miles per month. High ambient temps seem to exacerbate cycling losses, as we have learned in Phoenix.