LEAF's "gradual capacity loss NOT covered" battery warranty

I dunno know if this belongs here in "General / Main Owners Forum" or in "Range / Efficiency / Carwings" or in "Batteries & Charging", but, here goes.

I was having a bit of a "discussion" with an EV skeptic who asked how long the battery lasts. I trotted out the party line of "80% capacity after 10 years". He raised an eyebrow and asked "How do you know that? Is that what Nissan tells you? It seems like I'm always buying batteries for my laptop every couple of years." I should have mentioned that such is how Nissan warranties the battery, but I forgot about that so I started hem-ing and haw-ing about how laptop batteries are not cooled, how they have cylindrical cells and run hotter, how heat is a battery's enemy, etc.

Later, I remember the battery warranty, but then I wonder, what's the official terms of the battery warranty? I went searching and found in Nissan's LEAF Warranty Information Booklet, on page 12:

The Lithium-ion battery (EV battery), like all lithium-ion
batteries, will experience gradual capacity loss with time
and use. Loss of battery capacity due to or resulting
from gradual capacity loss is NOT covered under this
warranty.

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I Google'd for "battery warranty" within mynissanleaf.com. The top three threads show latest posts dated back in Nov 2010. I was not able to find any recent information on what people think about the "gradual capacity loss is NOT covered" clause of the battery warranty. Is anybody bothered by Nissan's "gradual capacity loss is NOT covered" battery "warranty"? What's your plan if you think your battery is losing capacity faster/more than it should?

My delivery is "pending in April" and this battery non-warranty gives me a bit of a chill in my feet...

The Nissan battery is not actively cooled either. There has been discussions of this in many places on the forum. There are many who plan to lease so that the battery issue is moot for three years. Certainly by the third year we should have a lot of real world data to know the rate of capacity loss. My thought is that by then the value of used Leafs will be quite dependant on that data-- if batteries hold up well the car will be worth far more than the 45% residual that Nissan is figuring. If there is reason for concern it will be worth less than that-- but leasees will have Nissan carry that risk, while buyers are taking that on themselves.

I haven't decided which way I am going, I want to see the numbers side by side and decide based on the difference between leasing then buying and just buying outright. I think I am willing to pay 1,000 more for the assurance the lease provides, but some have suggested that the differential may be more than that.

There was a "Will you cancel your purchase without a capacity warranty?" poll and a 16-page thread on this issue when the terms of the battery warranty were first revealed. Read it and vote here:
http://www.mynissanleaf.com/viewtopic.php?f=9&t=1709

TT

Laptop usage is pretty different from EV charging. Laptops are frequently left plugged in for long periods of time (100% charged), or allowed to run all the way to zero for long periods of time. Both are bad for lithium longevity.

It is unclear what happens to a Nissan LEAF after it is returned from a typical lease.

A. Will Nissan subject a lease return vehicle to some rigorous multi-point vehicle test before it being re-released back into the market?

B. Will Nissan swap out the battery before they re-release it back into the market?

C. Or worst case, the return leased vehicle is "dealer inventory" and the dealers simply decide what they wish to do with the vehicles....

Just wondering....

There are many unanswered questions regarding the LEAF battery and mode of capacity fade. If one of the modules degrades more rapidly than the others, it could conceivably be replaced at lower cost than the whole battery pack. If the whole pack degrades in concert, then this is a different problem, with higher cost for replacing the pack. Based on my experience with Nissan, I am giving them the benefit of the doubt and purchasing rather than leasing. Of the 3 major Japanese auto manufacturers, Nissan has the greatest experience with Li-ion batteries and their use in EVs.

There is NO Nissan warranty on the pack capacity of any kind at all, zero warranty coverage. That is the answer and for more discussion people should post here-

http://www.mynissanleaf.com/viewtopic.php?f=9&t=1709

I trotted out the party line of "80% capacity after 10 years"

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It seems that party line has changed to 70% after 8 to 10 years.

Googling will turn up a good number of references to Mark Perry citing the 70% number repeatedly over the past 6 months or more. The time range cited seems to vary from 8 years to 10 years.

Maybe someone with more "battery knowledge" can answer this. How does the number of years factor along with number of recharges? Can someone who drives 80 miles per day and does a home recharge each night hope to retain 70% in 8 to 10 years? Conversely, can the owner who only needs to charge once a week expect to see far longer battery life?

There is a lot of conjecture, mostly about other batteries or different chemistries, and it seems that Nissan has not published any use/lifetime data or graphs.

Generally, it is felt that even an unused battery will lose significant capacity over the years.

Some folks estimate that 2000 full charges or 4000 half-charges will be roughly equivalent, and possible before the battery drops too much below about 80%.

But, in my mind, it is not clear what we should expect from a GOOD, but high-usage battery, other than perhaps a 30% capacity loss over "some" number of years.

Chuckster said:

Maybe someone with more "battery knowledge" can answer this. How does the number of years factor along with number of recharges? Can someone who drives 80 miles per day and does a home recharge each night hope to retain 70% in 8 to 10 years? Conversely, can the owner who only needs to charge once a week expect to see far longer battery life?

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80 miles a day is a lot, and requires a deep cycling of the battery every day.. most likely you will not get that long a life, probably it includes long periods of hwy travel at high speeds (for me anything faster than 55mph is high). That would be around 20k miles a year far outside the normal patterns.

There is a battery life simulation study that was mentioned here, cant find the link now.. it has a lot of details on what determines life.. mostly it is the temperature of the battery and it will range from 6 year in Phoenix to 12 years in Seattle. The thread title is how to increase battery life or something like that.

Here is link to another article that discusses life of Li-ion batteries. This information is relevant to portable applications, but is also applicable for EVs.

http://powerelectronics.com/portable_power_management/battery_charger_ics/proper_care_extends-li-ion-battery-0425/index2.html

The article discusses techniques to boost battery life, and I have taken the liberty to paraphase some of them.

Use partial-discharge cycles - Using only 20% or 30% of the battery
capacity before recharging will extend cycle life considerably. As a general rule, 5 to 10 shallow discharge cycles are equal to one full discharge cycle.
Avoid charging to 100% capacity - Reducing the float voltage will increase
cycle life and service life at the expense of reduced battery capacity
Select the correct charge termination method - Selecting a charger that uses minimum charge-current termination (C/10 or C/x) can also extend battery life by not charging to 100% capacity
Limit the battery temperature - Limiting battery-temperature extremes extends battery life, especially prohibiting charging below 0°C.
Avoid high charge and discharge currents - High charge and discharge currents reduce cycle life. Some chemistries are more suited for higher
currents such as Li-ion manganese and Li-ion phosphate. High currents place excessive stress on the battery.
Avoid very deep discharges (below 2 V or 2.5 V) - Very deep discharges will quickly, permanently damage a Li-ion battery.

These techniques have been discussed in various threads on MNL but is useful to remind ourselves on the limitations of the Li-ion technology.

Herm said:

There is a battery life simulation study that was mentioned here, cant find the link now.. it has a lot of details on what determines life.. mostly it is the temperature of the battery and it will range from 6 year in Phoenix to 12 years in Seattle. The thread title is how to increase battery life or something like that.

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linkim said:

Here is link to another article that discusses life of Li-ion batteries. This information is relevant to portable applications, but is also applicable for EVs.

http://powerelectronics.com/portable_power_management/battery_charger_ics/proper_care_extends-li-ion-battery-0425/index2.html

The article discusses techniques to boost battery life, and I have taken the liberty to paraphase some of them.

Click to expand...

We have to be careful with information like this because it's too easy to get confused or worried. For example:

linkim said:

Use partial-discharge cycles - Using only 20% or 30% of the battery capacity before recharging will extend cycle life considerably. As a general rule, 5 to 10 shallow discharge cycles are equal to one full discharge cycle.

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There's no magic here. We can use our full allowable capacity in one 'sitting' for one 100 mile cycle, or we can drive 20 miles a day for five days. If we redefine our 20 mile days as a 'cycle' then it appears we have a longer life. We can eat the M&Ms in one sitting or eat a couple a day. In the end, it's still only one bag of M&Ms.

linkim said:

Avoid charging to 100% capacity - Reducing the float voltage will increase cycle life and service life at the expense of reduced battery capacity

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The Leaf already does this. The car's management system will not let us use full 100% capacity - we're already restricted to about 80%. We can restrict charging additionally if we choose (charging to consumer 80%) but the gain is smaller than the initial restriction from 100% of ultimate capacity to 80% of ultimate.

linkim said:

Select the correct charge termination method - Selecting a charger that uses minimum charge-current termination (C/10 or C/x) can also extend battery life by not charging to 100% capacity

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The car already does this.

linkim said:

Limit the battery temperature - Limiting battery-temperature extremes extends battery life, especially prohibiting charging below 0°C.

Click to expand...

The car already does this.

linkim said:

Avoid high charge and discharge currents - High charge and discharge currents reduce cycle life. Some chemistries are more suited for higher currents such as Li-ion manganese and Li-ion phosphate. High currents place excessive stress on the battery.

Click to expand...

The car already does this. The owner's manual suggests that if we avoid jack-rabbit starts that'll help with battery life. After controlling charge and discharge current by properly sizing the motor and inverter and controlling the amount of energy recovered by regenerative braking, the last large current spike comes from taking off from a standing start.

linkim said:

Avoid very deep discharges (below 2 V or 2.5 V) - Very deep discharges will quickly, permanently damage a Li-ion battery.

Click to expand...

The car already protects us from this - we can't discharge below 3.0V.

linkim said:

These techniques have been discussed in various threads on MNL but is useful to remind ourselves on the limitations of the Li-ion technology.

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Yes - good reminders - especially if we're designing and building our own battery. They're only of fringe value for those of us buying a Leaf, however, as this work has already been done by Nissan's engineers and we simply do not have to worry about it.

All tech has limits - absolutely. It's very good to know that our lithium batteries are significantly better than the lead-acid and NiMH that's come before.

Good points AndyH. Clearly the LEAF has a highly sophisticated BMS to keep the consumer from murdering the pack.. However, within the allowable sandbox we get to play, are you planning any strategies to extend the life of your pack? That is what I would find interesting.

AndyH said:

We have to be careful with information like this because it's too easy to get confused or worried.

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I agree, you have to be careful with most of the information you find on the internet. One way is to vett the information by the source, and I prefer to believe results from peer-review journals. The link I posted was based on results for portable electronic devices, but as I stated, I think they are useful for Li-ion batteries for EV application. Clearly, there are more data for Li ion batteries in portable devices and much of the research on EV batteries start with single cells. Tesla uses cells developed for portable applications so there is a connection.

Yes linkim there is a connection - the info absolutely does apply and I'm not in any way suggesting that it does not.

HOWEVER - and this is a significant however - peer-reviewed engineering papers are looking at a bare cell on a bench. They're talking about how to protect RAW CELLS as they're assembled into a finished battery and then put to work in the real world.

Nissan engineers have already done the battery design and management work. We are not allowed to do anything to the battery that would hurt it - and that's a very good thing!

While the engineering-side papers are interesting background for those geeks that are interested in the work Nissan engineers did to protect our cars from us, they're NOT very useful beyond that point -- because a properly engineered battery does not allow the consumer to ever get into a battery danger zone.

ENIAC said:

Good points AndyH. Clearly the LEAF has a highly sophisticated BMS to keep the consumer from murdering the pack.. However, within the allowable sandbox we get to play, are you planning any strategies to extend the life of your pack? That is what I would find interesting.

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Thanks ENIAC. I'm still working on my own process, and now that I've moved from May(be) to penduary I've got more time to think about it.
At this point, I plan to plug the car in, then unplug and drive it. I'll probably charge to 80% and recharge every couple of days because that'll give me the range I need. I don't have any reservations about charging to 100% though and will do that as needed for longer drives.

I work with raw lithium cells and battery management systems daily and frankly, I'm SO looking forward to using the Leaf like a 'toaster' - plug it in and it works. :lol:

Does lower current equate to lower voltage or does voltage not make a difference?

DaveinOlyWA said:

Does lower current equate to lower voltage or does voltage not make a difference?

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For rechargeable batteries, on discharge, lower current means higher voltage. On charge lower current is associated with lower voltage. For the same charge/discharge current, the closer the two voltages are, the higher the voltaic efficiency.

AndyH said:

Nissan engineers have already done the battery design and management work. We are not allowed to do anything to the battery that would hurt it - and that's a very good thing!

While the engineering-side papers are interesting background for those geeks that are interested in the work Nissan engineers did to protect our cars from us, they're NOT very useful beyond that point -- because a properly engineered battery does not allow the consumer to ever get into a battery danger zone.

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Hi AndyH,
I initially started out to mention a link to some work reported on battery life that involved Li-ion cells for portable electronics because there was a question on capacity fade. My point is not to debate the engineering or BMS of battery packs for EVs. You have more experience on these aspects than me. My experience is with R&D on Li-ion cells so I tend to reference results based on single cells, which IMHO provide valuable information that can be a guide to battery performance relevant for EVs.

I agree with you that Nissan does try to protect the consumer from putting the battery in a danger zone. However, that doesn't mean some inquisitive minds haven't tried to see what makes the battery and BMS function. It wouldn't surprise me if some adventuresome owner attempts to add an extra battery pack to the LEAF to extend the range.

I appreciate an enthusiast like you, present owners and others on the MNL forum who provide a valuable service by sharing your knowledge/experience so we can all learn what to expect with the use of the LEAF. My goal is to achieve a reasonable driving distance with the LEAF, and with minimal hassle to reliably charge it.