Battery Replacement Program Details

[TomT]

I don't think it is much of a deal in Washington regardless... It just doesn't get that warm there for long enough...

If you're worried about heat, just do what I do, and then forget about it. Use the car as much as possible because the batteries will degrade whether used or not.

 

[cgaydos]

Is it possible that even when the car is only exposed to 85-95 degree heat for a short period (2-3 weeks) that degradation is accelerated? I think that is why we see more degradation in mild southern California climate then we do in say the Northwest. Maybe it only takes a week of 90 degree weather to do damage. It is interesting that Steve Marsh in WA only saw 22% degradation @ 100,000 miles and he beats the living hell out of his battery.

I live in Taos where the climate only goes above 90 for 2-3 weeks. When I get a Leaf or an I-Miev I plan on running the AC during the day when the car is sitting in the shade during this period and maybe even run a swamp cooler under the car.

It seems like more damage is done during this 3 week period then the rest of year combined?

Thoughts?

I don't think there is enough data to be ultra-precise about battery degradation, but yes you are on to something. Outside of heat the two biggest predictors are age and miles driven. There are other factors but they appear to have only slight impacts on longevity.

The problem is knowing just how much damage is done if the battery temp is at 80F for a day, or 90F, and so on ... although we believe that the heat impact is greater if the battery is at 100% charge during the heat wave. So it's hard to say that 3 weeks at 90F will do more battery damage than the rest of the year combined - but it will do some additional damage.

A key is that it's the temp of the battery, not necessarily ambient temps. In low-humidity Taos (a wonderful town, by the way) parking in a shaded spot which has temps lower than outside will protect the battery from the heat. On our rare 90F days in our also low-humidity climate my garage - which has an apartment above that absorbs the heat from the direct sunlight - is usually cooler at maybe 72-76F. On the other hand, parking under a tree in the town plaza won't provide the same heat protection.

Another key is that the battery has a very slow heat transfer rate. So if you start in a cool garage, drive 10 miles through heat to another cool garage, the time in the heat probably won't raise the battery temps anywhere close to the ambient temp (although using the battery does raise the temp, too, as does charging it).

I don't think running the A/C in the car while parked in the shade will help keep the battery cooler - in fact since it will be draining battery power it may have the opposite effect.

 

[Stoaty]

On the topic of capacity loss and temperature, I noted that during the summer (4 days per week parked in full sun in the San Fernando valley with temps up to 100 degrees) my capacity was dropping like a rock. For the last 4 months (late fall/winter), parked in the same spot for work, the capacity loss has basically stopped cold. I think the rate of capacity loss in winter is about 20% the rate of capacity loss in the summer. Expecting that by June or July the loss will ramp up again.

 

[EV4Taos]

Thank you. This is the kind of feed back I was looking for. Very helpful!

I still might blow the swap cooler under the pack for the 2 hottest weeks, but I think your right about the AC; could make the battery hotter.

 

[cgaydos]

Thank you. This is the kind of feed back I was looking for. Very helpful!

I still might blow the swap cooler under the pack for the 2 hottest weeks, but I think your right about the AC; could make the battery hotter.

Certainly an idea worth exploring, if the ambient temps in the shaded parking spot are over 80F for hours on end.

 

[cgaydos]

On the topic of capacity loss and temperature, I noted that during the summer (4 days per week parked in full sun in the San Fernando valley with temps up to 100 degrees) my capacity was dropping like a rock. For the last 4 months (late fall/winter), parked in the same spot for work, the capacity loss has basically stopped cold. I think the rate of capacity loss in winter is about 20% the rate of capacity loss in the summer. Expecting that by June or July the loss will ramp up again.

Very interesting - and I very much appreciate all the work you've done on capacity loss data.

I'm going to offer this anecdote for consideration in thinking about how the various factors work together. Our 2011 LEAF was delivered in October 2011 to the Nissan Dealer in Baytown, Texas (next to Houston). It stayed there for 16.5 months until early March, 2013, when I bought it as a demo with 1624 miles and had it shipped to Colorado. I've never been to Baytown but per on-line sources the weather seems to benefit from a "Gulf effect" and isn't quite as hot as nearby inland areas - July and August average peak temps at 92F and min temps of 76F. So this LEAF basically sat outside and baked for one Baytown summer, apparently often at 100% charge, plus two winter seasons.

Tested at arrival it appeared to have about 6-8% battery degradation. We tested range against our 4-month old (actually 6 months since arrival at dealership) 2012 LEAF, with then 5000 all-winter miles, and the 2012 LEAF demonstrated maybe 3-4% more range in identical situations.

So, by itself one summer of heat just sitting in the lot didn't appear to do that much more battery damage than just sitting there in moderate temperatures would have done. Perhaps because it was rarely driven anywhere, thus the battery had few charge/discharge cycles?

 

[EV4Taos]

Considering your Leaf from Texas had twice as much degradation (6-8%) with a 1/3 less miles on it as your Colorado Leaf (3-4%), heat seems to be a major factor here.

Degradation is the cause by plating on the SEI layer of NMC batteries, so I think heat becomes a bigger factor after 20,000 miles. My concern is not so much under 20,000 miles (unless you live in Phoenix), but between 20,000-100,000 miles. I will most likely be buying a Leaf in the 20k-40k range, so I would like to get at least 50 miles (40 miles to ski valley) of range in 5F weather for 4 to 5 years of ownership. I'll do anything I can to protect the battery during the summer, so I can see squeak through 5 years. I am betting if I don't let the battery get too hot a 7.5 year old leaf will have 70% capacity in Taos.

More thoughts?

 

[DaveEV]

Is it possible that even when the car is only exposed to 85-95 degree heat for a short period (2-3 weeks) that degradation is accelerated?

The rate at which the battery loses capacity due is easily estimated using Arrhenius' equation.

Rule of thumb: For every 10C increase in battery temperature, you double the rate of capacity loss.

3 weeks of 90F heat (32C) is like 6 weeks of 72F heat (22C).

I think the rate of capacity loss in winter is about 20% the rate of capacity loss in the summer.

Which is about right. If in the winter the battery is around 60F (15C) and in the summer the battery is around 95F (35C), in the summer the battery should age 4 times faster.

That said, I do think that there appears to be a good amount of lag in the reported capacity. For example, my reported Ah has been hovering around 54.0 Ah +- 0.1 Ah since Jan 1. That's 4+ months of the same Ah reading with battery temps mostly in the upper 60F low 70F range. But the previous 4 months averaged around 0.4 Ah / month of loss, and pretty linear across those months.

So, by itself one summer of heat just sitting in the lot didn't appear to do that much more battery damage than just sitting there in moderate temperatures would have done. Perhaps because it was rarely driven anywhere, thus the battery had few charge/discharge cycles?

It does make sense that avoiding cycling the battery in high temps could limit the effect of high temps - especially if the state of charge is kept low which is possible.

 

[surfingslovak]

Degradation is the cause by plating on the SEI layer of NMC batteries, so I think heat becomes a bigger factor after 20,000 miles. My concern is not so much under 20,000 miles (unless you live in Phoenix), but between 20,000-100,000 miles. I will most likely be buying a Leaf in the 20k-40k range, so I would like to get at least 50 miles (40 miles to ski valley) of range in 5F weather for 4 to 5 years of ownership.

No, this is incorrect. The model Stoaty empirically derived from owner data shows that the rate of degradation slows with age, but it's nearly imperceptible by the owner.

 

[cgaydos]

Considering your Leaf from Texas had twice as much degradation (6-8%) with a 1/3 less miles on it as your Colorado Leaf (3-4%), heat seems to be a major factor here.

Definitely, but given that the Texas LEAF was 3x "older" (measured by time since delivery to dealer) how much of that was heat and how much age? Not expecting answers, just pointing out that while we have sufficient data to draw good conclusions regarding major factors, the data just aren't precise enough especially regarding how the different factors interact.

 

[EV4Taos]

No, this is incorrect. The model Stoaty empirically derived from owner data shows that the rate of degradation slows with age, but it's nearly imperceptible by the owner.

What your saying is true and is probably what Nissan is banking on with their battery warranty. I'm just trying to say that its easier to see degradation at 20K miles than it is a 5K. Granted I said it poorly.

Is there anyway to get the full version of this chart? Its very interesting. It would be nice to know what the colors mean.

Definitely, but given that the Texas LEAF was 3x "older" (measured by time since delivery to dealer) how much of that was heat and how much age? Not expecting answers, just pointing out that while we have sufficient data to draw good conclusions regarding major factors, the data just aren't precise enough especially regarding how the different factors interact.

Very true, age is a big factor. Thought it would have been nice if the your older Leaf was sitting in the Northwest instead of Texas. That would give us degradation mostly from calendar life and not so much weather/heat.

 

[DaveinOlyWA]

What your saying is true and is probably what Nissan is banking on with their battery warranty. I'm just trying to say that its easier to see degradation at 20K miles than it is a 5K. Granted I said it poorly.

well that is stating the obvious since your need is less covered at 20K miles than 5 K miles. it is however, a valid concern which is why we are in so much a better position now since we do have monitoring equipment from day one...

obtw; my degradation has begun and it was about 5100 miles...

 

[Reddy]

Considering your Leaf from Texas had twice as much degradation (6-8%) with a 1/3 less miles on it as your Colorado Leaf (3-4%), heat seems to be a major factor here.

Degradation is the cause by plating on the SEI layer of NMC batteries, so I think heat becomes a bigger factor after 20,000 miles. My concern is not so much under 20,000 miles (unless you live in Phoenix), but between 20,000-100,000 miles. I will most likely be buying a Leaf in the 20k-40k range, so I would like to get at least 50 miles (40 miles to ski valley) of range in 5F weather for 4 to 5 years of ownership. I'll do anything I can to protect the battery during the summer, so I can see squeak through 5 years. I am betting if I don't let the battery get too hot a 7.5 year old leaf will have 70% capacity in Taos.

More thoughts?

Whoa, wait a minute here. At 5 F you may have trouble achieving 50 mi even with a new Leaf, depending upon heat use and speed driven. Search out cold weather links on the forum, I've posted many links before in the past. However, with Taos' higher elevation, low humidity (e.g., cooler nights), you should be able to keep the battery a lot cooler than most in the south. Come to think of it, other high altitude Leafers have posted some impressive distances due to the higher altitude (fewer air molecules to generate wind resistance).

 

[cgaydos]

Whoa, wait a minute here. At 5 F you may have trouble achieving 50 mi even with a new Leaf, depending upon heat use and speed driven. Search out cold weather links on the forum, I've posted many links before in the past. However, with Taos' higher elevation, low humidity (e.g., cooler nights), you should be able to keep the battery a lot cooler than most in the south. Come to think of it, other high altitude Leafers have posted some impressive distances due to the higher altitude (fewer air molecules to generate wind resistance).

So first, the 40 miles is round trip between Taos and the Ski Valley, and a climb of 2200 ft one way. Even my 2011 with the heater on full could make that on a 0 F day with several bars to spare - and the nice part is that the descent is on the return so you can charge to 100% and not worry about not getting regeneration during the start of the trip, and possibly even a gain a bar on the way back due to regeneration.

Second, 50 miles at 5 F is not a problem with a new LEAF, especially the SV or SL with the heat pump. For my older 2011 and 2012 LEAFs with the degraded battery and inefficient heating coils we sometimes have to go periods of time without heat to eek out 50 miles at when ambient temps are low. Note, that when the 2012 was new we regularly did 58 mile round trips in temps like that without hitting the very low battery warning.

One advantage of Taos is that in whichever direction you drive the two-lane roads will tend to encourage reasonable speeds without a lot of stop-and-go - if you're driving a pretty steady 60 mph you'll get more miles out of the same battery.

 

[KJD]

Hi everyone. Brian Brockman from Nissan Communications again.

Hey Mr Brockman, long time no see.

 

[Stoaty]

Hey Mr Brockman, long time no see.

Kay: See ya around, Jay.

Jay: No, you won't.

MIB

 

[ttweed]

Hi everyone. Brian Brockman from Nissan Communications again.

Hey Mr Brockman, long time no see.

Interesting that Mr. Brockman's last post to the forum was in 2013, but his last visit to the forum was April 7, 2014. Is he lurking but not talking? It would be nice to hear some official update on this subject.

TT

 

[Nubo]

Hey Mr Brockman, long time no see.

Kay: See ya around, Jay.

Jay: No, you won't.

MIB

IIRC, that whole battery thing was really just the light of Venus refracted by some swamp gas. :mrgreen:

 

[TomT]

Weather balloons! :lol:

Hey Mr Brockman, long time no see.

Kay: See ya around, Jay.
Jay: No, you won't.
MIB

IIRC, that whole battery thing was really just the light of Venus refracted by some swamp gas. :mrgreen:

 

[walterbays]

Hi everyone. Brian Brockman from Nissan Communications again.

Hey Mr Brockman, long time no see.

Interesting that Mr. Brockman's last post to the forum was in 2013, but his last visit to the forum was April 7, 2014. Is he lurking but not talking? It would be nice to hear some official update on this subject.

I expect we will hear nothing until Nissan has something very good to say about batteries. I agree it would be nice if Mr. Brockman were giving us information, and I believe if he were then more drivers would wait for the improved batteries and improved battery replacement plan(s) rather than switching from Nissan.

However, given that Nissan won't release any preliminary information then I do prefer for Mr. Brockman to be here silently listening to us, than not to be here at all.