Capacity Loss on 2011-2012 LEAFs

JeremyW said:

It's gotten so bad that I'm seriously considering getting a used portable air conditioner off craigslist.

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Jeremy, I think you are doing more than could be reasonably expected. I wouldn't worry about it too much if I was leasing. Who knows, maybe we'll see some big break-trough in battery technology next year, and all of this will be moot anyway.

edatoakrun said:

The results from 8/30/12 were:

97.3 miles to VLB, 98.9 miles in total, by the odometer.

CW: 96.5 (~2.5% under-report) total miles, at 5.7 m/kWh, 16.8 kWh used from 100% to about the same capacity level, slightly past VLBW.

Compare this test with my first test on 9/7/11:

91.5 miles to VLB, 93.4 in total, by the odometer

CW: 91.1 (~2.5% under-report) total miles, at 4.9 m/kWh, 18.7 kWh used from 100% to about the same capacity level, slightly past VLBW.

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Ed, did you use 2 kWh less energy for the range test this year? That would be consistent with the performance I saw in my Leaf recently. It's good to see such energy economy numbers. They seem to be often higher than last year, which is great.

Herm said:

JRP3 said:

Higher energy density cells, which do exist, could be installed and still allow room for a TMS. It is not technically impossible, though it may not be a cost effective retrofit. Or there is other lithium chemistry that are possibly not as susceptible to heat issues. SCIB and A123 are possibilities.

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I also dont think its prohibitively expensive to retrofit an active cooling system.. it could be done without opening up the battery pack but its likely you will need to drop it to install the insulation.

The battery modules are in thermal contact with each other and with the bottom of the battery case, not the sides or the top. Attach 4 AC condensor plates to each corner of the bottom of the case, add a diverting/metering freon valve and hook it up to the AC circuit. It will not be as sophisticated as the system used in the Volt but it will cool all the cells, you may need to do a bit more balancing since all the modules will not have an equal temperature but at least it will be low. Yes your range will be reduced so the upgrade should be made optional. Once the cells reach 60% SOC it will stop any attempt to cool.

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OK a hopeful idea. Granted, the pack would be actively cooled during charging, at the expense of charging energy economy. But even if Nissan could do that, and I doubt that they would be able to engineer, test and roll out such a major revision in less than two years of testing, crash testing, EPA testing and approvals, how would that actually help improve driving range? Cars that sit unplugged in hot environments for many hours, such as in outdoor parking lots at work sites, would draw down the SOC quickly by powering their AC systems for pack cooling. If pack cooling is shut down at some point, 60%, 50%, whatever you choose, then the pack will return to hot ambient temperature quite quickly. The packs would still bake and you'd have reduced driving range by running the AC for hours before the SOC hit the cutoff.

This is something that I've been wondering about with the Ford Focus EV. Apparently, that car reminds the owner to plug in when it's in a hot environment. What if there is no plug available for 8 hours of a work day? Does the car use its active TMS, running down the SOC, or does the pack bake?

It seems that a less heat sensitive pack chemistry must be at least part of the solution.

surfingslovak said:

edatoakrun said:

The results from 8/30/12 were:

97.3 miles to VLB, 98.9 miles in total, by the odometer.

CW: 96.5 (~2.5% under-report) total miles, at 5.7 m/kWh, 16.8 kWh used from 100% to about the same capacity level, slightly past VLBW.

Compare this test with my first test on 9/7/11:

91.5 miles to VLB, 93.4 in total, by the odometer

CW: 91.1 (~2.5% under-report) total miles, at 4.9 m/kWh, 18.7 kWh used from 100% to about the same capacity level, slightly past VLBW.

Click to expand...

...Ed, did you use 2 kWh less energy for the range test this year? That would be consistent with the performance I saw in my Leaf recently. It's good to see such energy economy numbers. They seem to be often higher than last year, which is great.

Click to expand...

Actually, I hope I made it clear in my entire post on the other thread, that I believe my m/kWh reports from my dash, nav screen, and CW, and so also the kWh use numbers you quoted above, are probably not correct.

Please take another look.

surfingslovak said:

Jeremy, I think you are doing more than could be reasonably expected. I wouldn't worry about it too much if I was leasing. Who knows, maybe we'll see some big break-trough in battery technology next year, and all of this will be moot anyway.

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Oh, totally. But hey, I'm having fun with it. We've still got another month of heat up here, and dang it I want to see five TB's!!! And yeah, I've got a lease, but I think it may be too long if I don't get a replacement sometime in the future. :shock:

On a side note, check out this PDFof the experiences of the Gen 1 Rav4 EV owners. There's a few historical repeats in there. :roll:

My favorite part:

The Nickel Metal Hydride traction battery used in the RAV4-EV was made by Panasonic EV, and dubbed the
model EV-95, to represent its amp-hour capacity rating. It is essentially a second generation NiMH, an
improvement (higher capacity) over the ECD model used in the GM EV-1 Gen II. The traction pack performs
admirably, when air cooled as here and is arranged as three rows positioned underneath the cabin area beneath
the floorboards. Weighing about 1000 pounds, it has an energy capacity of 26 kWh, and provides over 100
freeway miles at 65 miles per hour in good condition. Even with over 100,000 miles, this pack still can
deliver this same kind of freeway performance.

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While I don't think those 100,000 mile packs were in AZ, part of me wonders if the oil industry bought a really, really good battery patent. :roll: I'm starting wonder if NiMH will in fact make a comeback after the patent expires.

Jeremy

surfingslovak said:

Ed, did you use 2 kWh less energy for the range test this year? That would be consistent with the performance I saw in my Leaf recently. It's good to see such energy economy numbers. They seem to be often higher than last year, which is great.

Click to expand...

That's not the only possible conclusion here. Another one is that the car is reporting less energy usage for the same amount of consumption. Or some combination of both inaccurate consumption numbers AND less battery capacity. Considering that we calculate battery capacity from the consumption numbers, there is no easy way to differentiate the two except to measure wall energy for a recharge.

And, no, I am not saying this is the problem in AZ, but with TickTock's car it appears it was part of it.

JeremyW said:

While I don't think those 100,000 mile packs were in AZ, part of me wonders if the oil industry bought a really, really good battery patent. :roll: I'm starting wonder if NiMH will in fact make a comeback after the patent expires.

Jeremy

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Not likely. Don't forget many of the original RAV packs did not make it to 100K miles and have been replaced, and though it does seem a durable chemistry it also has worse charge efficiency, lower specific energy density, lower volumetric energy density, and higher self discharge. I think continued improvements in lithium chemistry will eventually make lithium even better than it is, and it's already better than NiMH in most aspects. Nissan just picked the wrong version of lithium batteries to run without a TMS. A simple cooling loop tied to the A/C, and a heating loop tied to the heater, with an insulated battery enclosure, would have probably eliminated these heat issues and provide better cold weather range. The A/C need not run all the time, just cooling the pack when plugged in and charging would probably make a huge difference in capacity preservation.

RegGuheert said:

jspearman said:

I don't see how Nissan will be able to avoid a full recall at this point.

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I guess I don't see that happening since many (most?) LEAFs are likely to meet the expectations set forth by Nissan. For those that fall way short, I would expect to see some sort of warranty put in place.

The issue will be for those cars that fall short, but not way short. I expect Nissan to stick with their party line of "It's normal," for owners of those cars.

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I can't see how they can stick with that if they intend to sell many EVs. The general public is skittish enough about electric vehicles. With horror stories AND lack of warranty, they're going to stay away in droves. I've got to believe that Nissan understand this and aren't going to piss away their investment or their future, for which Goshn rightfully asserts that EVs are a necessity if the personal automobile is to survive.

This does point to a disconnect in Nissan somewhere, so far. I think they have a lot of folks really committed to the LEAF's success but somewhere in the chain, "Go Fever" took hold and someone or some group told higher-ups what they *thought* they wanted to hear, instead of what they needed to know. I've seen this more than once in personal experience.

Boomer23 said:

Herm said:

I also dont think its prohibitively expensive to retrofit an active cooling system.. it could be done without opening up the battery pack but its likely you will need to drop it to install the insulation.

The battery modules are in thermal contact with each other and with the bottom of the battery case, not the sides or the top. Attach 4 AC condensor plates to each corner of the bottom of the case, add a diverting/metering freon valve and hook it up to the AC circuit. It will not be as sophisticated as the system used in the Volt but it will cool all the cells, you may need to do a bit more balancing since all the modules will not have an equal temperature but at least it will be low. Yes your range will be reduced so the upgrade should be made optional. Once the cells reach 60% SOC it will stop any attempt to cool.

Click to expand...

OK a hopeful idea. Granted, the pack would be actively cooled during charging, at the expense of charging energy economy. But even if Nissan could do that, and I doubt that they would be able to engineer, test and roll out such a major revision in less than two years of testing, crash testing, EPA testing and approvals, how would that actually help improve driving range? Cars that sit unplugged in hot environments for many hours, such as in outdoor parking lots at work sites, would draw down the SOC quickly by powering their AC systems for pack cooling. If pack cooling is shut down at some point, 60%, 50%, whatever you choose, then the pack will return to hot ambient temperature quite quickly. The packs would still bake and you'd have reduced driving range by running the AC for hours before the SOC hit the cutoff.

Click to expand...

Consider cooling the battery pack to about 70F each night before or during charging, and again in the morning (similar to the climate timers). The battery is massive enough that it likely wont warm up much during the day - and a little insulation would go a long way. Don't bother cooling it when unplugged. Everyone plugs in at least once a day, right?

The pack would still warm up, but time above 90F would be greatly reduced, and wouldn't get as hot as a never-cooled pack.

I wouldn't circulate freon... but chilled water is a very good alternative. Fewer opportunities for freon leaks, water leaks are cheap to fix, and water is cheap to replace. While you're at it, use the water loop to keep the battery warm in place of the battery heaters (maybe not - I don't know how the battery heaters are installed.)

Not that any of this would be part of a retro-fit. This would be better suited for a (re)design. It would also depend on having a higher power charger to power the A/C and still have something left to charge.

JRP3 said:

I think continued improvements in lithium chemistry will eventually make lithium even better than it is, and it's already better than NiMH in most aspects. Nissan just picked the wrong version of lithium batteries to run without a TMS.

Click to expand...

+1

JeremyW said:

On a side note, check out this PDF of the experiences of the Gen 1 Rav4 EV owners. There's a few historical repeats in there. :roll:

Click to expand...

Nice find! Be sure to visit the RAV4 EV 100k club created by darelldd. One of my favorite EV sites.

RegGuheert said:

That's not the only possible conclusion here. Another one is that the car is reporting less energy usage for the same amount of consumption. Or some combination of both inaccurate consumption numbers AND less battery capacity. Considering that we calculate battery capacity from the consumption numbers, there is no easy way to differentiate the two except to measure wall energy for a recharge. And, no, I am not saying this is the problem in AZ, but with TickTock's car it appears it was part of it.

Click to expand...

I missed your comment, I'm sorry. Yes, you are absolutely correct. One more thing I should note: I drove the car down to turtle quite a few times to perform a range test, record the total usable energy and measure the kWhs needed to charge it back up to full. This data shows declining total capacity and range. Starting with 3-5% last winter, up to about 8-10% this summer. This type of loss would be roughly consistent with the 15% reported from Casa Grande a month ago. Obviously, this behavior could be caused by a software bug. For what it's worth, I've been monitoring pack voltage for about 8 months now. I would consider this to be a source of truth, and although it does fluctuate a bit, it was never below 393 Volt. Typically, it's 394 or 394.5 Volt after a full charge.

surfingslovak said:

JRP3 said:

I think continued improvements in lithium chemistry will eventually make lithium even better than it is, and it's already better than NiMH in most aspects. Nissan just picked the wrong version of lithium batteries to run without a TMS.

Click to expand...

+1

JeremyW said:

On a side note, check out this PDFof the experiences of the Gen 1 Rav4 EV owners. There's a few historical repeats in there. :roll:

Click to expand...

Nice find! Be sure to visit the RAV4 EV 100k club created by darelldd. One of my favorite EV sites.

RegGuheert said:

That's not the only possible conclusion here. Another one is that the car is reporting less energy usage for the same amount of consumption. Or some combination of both inaccurate consumption numbers AND less battery capacity. Considering that we calculate battery capacity from the consumption numbers, there is no easy way to differentiate the two except to measure wall energy for a recharge. And, no, I am not saying this is the problem in AZ, but with TickTock's car it appears it was part of it.

Click to expand...

I missed your comment, I'm sorry. Yes, you are absolutely correct. One more thing I should note: I drove the car down to turtle quite a few times to perform a range test, record the total usable energy and measure the kWhs needed to charge it back up to full. This data shows declining total capacity and range. Starting with 3-5% last winter, up to about 8-10% this summer. This type of loss would be roughly consistent with the 15% reported from Casa Grande. Obviously, this behavior could be caused by a software bug. For what it's worth, I've been monitoring pack voltage for about 8 months now. I would consider this to be a source of truth, and although it does fluctuate a bit, it was never below 393 Volt. Typically, it's 394 or 394.5 Volt after a full charge.

Click to expand...

How did you:....measure the kWhs needed to charge it back up to full.... ?

What do you mean by ...Starting with 3-5% last winter...?

How do you differentiate this from the seasonal decline from a colder battery?

I believe that I observed about a 5% maximum capacity decline last Winter, myself.

I have updated the Wiki with surfingslovaks table of estimated relative rate of battery capacity loss based on Arrhenius equation for rate of chemical reactions that 10 degree Celsius increase in temperature doubles rate of battery capacity loss:

http://www.mynissanleaf.com/wiki/index.php?title=Battery_Capacity_Loss#What_To_Do" onclick="window.open(this.href);return false;

Additions, corrections, etc. are welcome (especially from surfingslovak).

It was mentioned in a earlier post that some RAV4-EV's didn't make it to 100K miles on original batteries. However, many did. I owned a RAV4-EV that orginally came from San Diego. I took it to Michigan and then to the Florida Keys. When I sold it, ten years after it was built, it still had it's original Panasonic EV-95 pack. It still had the same range that it did when I bought it seven years before. Only a couple of the battery modules had any noticable impedence increase from new. I drove it 80 miles per day and usually had a 20 mile reserve. It had a simple air cooling system. I froze it in Michigan and cooked it in the Keys but it never seemed to bother the batteries. I know the Lithium batteries are superior on paper, but the track record of the EV-95 NiMH battery in the real world is incredible. I would trade the Lithium pack for a NiMH pack in a New York second (if they could be built---thanks Chevron :evil: ) even with the lower energy density and hence higher mass and physical size. Ten years from now it will be interesting to see how many (if any) LEAF's will have their orginal packs and orginal range.

Boomer23 said:

OK a hopeful idea. Granted, the pack would be actively cooled during charging, at the expense of charging energy economy. ... how would that actually help improve driving range? Cars that sit unplugged in hot environments for many hours, such as in outdoor parking lots at work sites, would draw down the SOC quickly by powering their AC systems for pack cooling. If pack cooling is shut down at some point, 60%, 50%, whatever you choose, then the pack will return to hot ambient temperature quite quickly. The packs would still bake and you'd have reduced driving range by running the AC for hours before the SOC hit the cutoff.

Click to expand...

It would not improve driving range, the purpose is to minimize battery degradation. The Volt consumes about 200Wh to keep the battery cool, even if its unplugged, a minimal use of energy. GM boasts that they are using "space age" insulation and apparently it is needed. Insulating the battery pack is crucial or you will quickly drain the battery in Phoenix.. you also want to prevent condensation from forming and that is a problem.
GM claims (and a recent study mentions it) that once the pack is discharged to 60% SOC it is fairly immune to heat degradation, thus at that point you can stop cooling the pack until it is plugged in again. True the its not exactly the same chemistry as the Leaf is using.

brettcgb said:

I wouldn't circulate freon... but chilled water is a very good alternative. Fewer opportunities for freon leaks, water leaks are cheap to fix, and water is cheap to replace.

Click to expand...

Chilled water is more complicated, now you have to add a chiller and a water pump.. there should not be too much trouble with freon leaks since this is an electric car.. no internal combustion engine shaking all the hose joints loose.. as a matter of fact I dont even see why they have to use rubber hoses... your fridge does not use any rubber hoses and it will hold a charge for decades. This is intended to be a jury rigged solution for existing Leafs, something that could be easily fitted at a dealership without having to open up the battery case.. obviously the factory can do a better job for new production. The factory could actually braze the freon loops to the bottom of the battery case itself, when they stamp those.

Herm said:

GM claims (and a recent study mentions it) that once the pack is discharged to 60% SOC it is fairly immune to heat degradation, thus at that point you can stop cooling the pack until it is plugged in again. True the its not exactly the same chemistry as the Leaf is using.

Click to expand...

Reference or link?

Herm said:

Boomer23 said:

OK a hopeful idea. Granted, the pack would be actively cooled during charging, at the expense of charging energy economy. ... how would that actually help improve driving range? Cars that sit unplugged in hot environments for many hours, such as in outdoor parking lots at work sites, would draw down the SOC quickly by powering their AC systems for pack cooling. If pack cooling is shut down at some point, 60%, 50%, whatever you choose, then the pack will return to hot ambient temperature quite quickly. The packs would still bake and you'd have reduced driving range by running the AC for hours before the SOC hit the cutoff.

Click to expand...

It would not improve driving range, the purpose is to minimize battery degradation. The Volt consumes about 200Wh to keep the battery cool, even if its unplugged, a minimal use of energy. GM boasts that they are using "space age" insulation and apparently it is needed. Insulating the battery pack is crucial or you will quickly drain the battery in Phoenix.. you also want to prevent condensation from forming and that is a problem.
GM claims (and a recent study mentions it) that once the pack is discharged to 60% SOC it is fairly immune to heat degradation, thus at that point you can stop cooling the pack until it is plugged in again. True the its not exactly the same chemistry as the Leaf is using.

Click to expand...

Sounds pretty feasible, at least energy-wise. I had assumed a larger cooling energy drain.

Scott: I lost my fourth bar today at 28,190 miles.
Me: Wow. Thought you had ditched the car by now.
Scott: It gets turned in September 15th.
Stoaty: I'm sorry for his loss. Can you provide details for the wiki?
Me: Sorry. That's all Scott told me.

opossum said:

Scott: I lost my fourth bar today at 28,190 miles.
Me: Wow. Thought you had ditched the car by now.
Scott: It gets turned in September 15th.
Stoaty: I'm sorry for his loss. Can you provide details for the wiki?
Me: Sorry. That's all Scott told me.

Click to expand...

LOL.



Is he terminating his lease?

He is.

opossum said:

Scott: I lost my fourth bar today at 28,190 miles.
Scott: It gets turned in September 15th.

Click to expand...

Well, I think it's safe to say that the car is well past the serviceable limits. Very sad, because it doesn't seem to even slow up on the way down.

I hope somebody will correct me, but I thought the capacity bars were 15%, then 7.5%, then 6.25%, etc. i cant find the actual Nissan chart. Anyhoo, four lost capacity bars is 15 + 6.25 + 6.25 + 6.25 =

33.75% minimum loss