Which factors have the biggest impact on battery life?

[Stanton]

I forgot that in US there are more problems with high temperatures than with low temperatures.
Not the case where I live but for hotter Leafs I made a little more research :ugeek:

Yes, it's all about the heat here in Texas (and much of the Southern US)!
There are several things you mention that I do already:
1) I don't "punch the pedal" or "slam on the brakes"...especially when hot
2) I timer charge to 80% a lot...except when I know I have a long trip (so I don't return empty)
3) I tend to drive in ECO when I hit LBW (about the only time I drive in ECO)

While I tend to be very careful about high SOC (like not charging to 100%/not charging when hot), I will pay more attention to low SOC than I used to (which hopefully will be much less with the new battery pack).

 

[dhanson865]

a. no reason for the 100% option because 100% is really 92-95% most of the time. Choosing 90% vs what you get at 100% is almost no change. Still I'd love to have the 60, 70, 80 options. I don't need both 90 and 100, just call it one or the other and I'm fine with that.

b. preheat how high, say to 50F if below 50F? Currently it only preheats to 20F. I'd be OK with raising it to preheat a little more but I wouldn't want it to go above 50F because degradation at higher temps and it takes so long to get rid of heat in the pack I'd rather have some buffer below ideal temp for the possibility it will heat up later that day.

Like others said, 90% and 100% of the accessible capacity. Also I want 90% because it is more efficient on the grid. I hope many know that getting that last 0,5kWh of juice takes a lot of time. And at below 4 temperature bars it is very very long process. But charging has parasitic load that is just wasted (relays, management modules, pump). 0,5kW from grid almost constantly and about the same into the battery. But it can take 1-3 hours. So there's a difference between 90% and 100%. Noticeable difference.

To be clear I mean no noticeable difference in range. I'm not claiming there isn't a noticeable difference in heat, power, time to complete charge and such.

I'm just trying to address the "I just bought a leaf and my car only goes 3 miles further at 100% than it does on 90% charge" style complaints.

and I'm assuming Nissan won't bother with the effort of trying to scale the SOC% between turtle and normal end of charging. I agree it'd be nice to have, I don't agree that Nissan will do it.

 

[dhanson865]

Not specifically for Leaf cells:

I find it hard to beleive that is an accurate curve for the 2011/2012 pack since they seem to have slow degradation above 40F/5C and fast acceleration above 70F/21C and yet that curve implies fast acceleration doesn't start until over 140F/60C

hmm it does say 50F/10C is as hot as you can get away with, I'd buy that as a reasonable temperature to stop charging at if you were somewhere cold and wanted to prolong battery life.

It's just sitting in the parking lot at work I see 86F/30C pack temps just sitting there baking on the asphalt. I have no choice to avoid the >50F pack temps unless I don't drive the car 8 months out of the year.

Even when it is below freezing outside my pack is hanging around at 45F to 50F in my garage and gets heated by the charging cycle. As soon as it gets above 60F outside my pack is going to drive above 50F and stay there for 8 months.

 

[edatoakrun]

...the 2011/2012 pack...seem to have slow degradation above 40F/5C and fast acceleration above 70F/21C ...

The actual capacity degradation results reported from the AVTA LEAF pack torture test conclusively prove that statement is incorrect (IMO).

="edatoakrun"
...Look at the capacity loss and average battery temperatures over the seasonal periods marked by 10,000 mile capacity tests:

There are very high rates of capacity loss at very high battery temperatures, which averaged over 104 F while charging for the DC LEAFs during the April to October 20 k miles driven, resulting in ~62% of the total average capacity loss over 50 k miles occurring during just those 20 k miles.

In contrast, over the only 10k miles driven entirely in the winter (January-March) but still with relatively high average battery temperatures of over 80 F (that's still higher than my warm-climate LEAFs average pack temperature is when it is charged in the early morning in mid-Summer!) the DC LEAFs only experienced ~9% of the total average capacity loss over 50k miles, less than one third of the rate of capacity loss reported from April to October.

What is missing, is data on how much lower capacity loss is at cooler pack temperatures, which almost all LEAFs experience for three-to-twelve months of the year....

http://www.mynissanleaf.com/viewtopic.php?f=27&t=14271&start=60

 

[Stanton]

It's just sitting in the parking lot at work I see 86F/30C pack temps just sitting there baking on the asphalt. I have no choice to avoid the >50F pack temps unless I don't drive the car 8 months out of the year.

I used to see the same thing...when I had to park outside at my old job (old battery pack).
Now that I've got covered parking, it should help in the long run.

 

[dgpcolorado]

Not specifically for Leaf cells:

I find it hard to beleive that is an accurate curve for the 2011/2012 pack since they seem to have slow degradation above 40F/5C and fast acceleration above 70F/21C and yet that curve implies fast acceleration doesn't start until over 140F/60C

hmm it does say 50F/10C is as hot as you can get away with, I'd buy that as a reasonable temperature to stop charging at if you were somewhere cold and wanted to prolong battery life.

It's just sitting in the parking lot at work I see 86F/30C pack temps just sitting there baking on the asphalt. I have no choice to avoid the >50F pack temps unless I don't drive the car 8 months out of the year.

Even when it is below freezing outside my pack is hanging around at 45F to 50F in my garage and gets heated by the charging cycle. As soon as it gets above 60F outside my pack is going to drive above 50F and stay there for 8 months.

That curve might be for the chemistry used in Tesla battery packs. As we have learned, Nissan's chemistry — while very safe from a fire perspective — is much more sensitive to heat than the Tesla battery chemistry.

Just guessing though. But we know perfectly well that Nissan's batteries wilt at temperatures in the 40ºC range. Florida batteries degrade rapidly even though they don't (usually) get even that hot, for example.

 

[dhanson865]

...the 2011/2012 pack...seem to have slow degradation above 40F/5C and fast acceleration above 70F/21C ...

The actual capacity degradation results reported from the AVTA LEAF pack torture test conclusively prove that statement is incorrect (IMO).

="edatoakrun"
...Look at the capacity loss and average battery temperatures over the seasonal periods marked by 10,000 mile capacity tests:

There are very high rates of capacity loss at very high battery temperatures, which averaged over 104 F while charging for the DC LEAFs during the April to October 20 k miles driven, resulting in ~62% of the total average capacity loss over 50 k miles occurring during just those 20 k miles.

In contrast, over the only 10k miles driven entirely in the winter (January-March) but still with relatively high average battery temperatures of over 80 F (that's still higher than my warm-climate LEAFs average pack temperature is when it is charged in the early morning in mid-Summer!) the DC LEAFs only experienced ~9% of the total average capacity loss over 50k miles, less than one third of the rate of capacity loss reported from April to October.

What is missing, is data on how much lower capacity loss is at cooler pack temperatures, which almost all LEAFs experience for three-to-twelve months of the year....

http://www.mynissanleaf.com/viewtopic.php?f=27&t=14271&start=60

It might point to the correct numbers being slightly higher but the gist of my statement is correct. The exact knee of the curve is unknown but it is obvious that the Leaf pack doesn't like higher temps.

If you think the AVTA data is all you need to know then go for it live your life around that data. I'm willing to look at other data as well.

 

[dgpcolorado]

This is what EVs need to start showing us. When I'm driving the car, I don't care whether the maximum allowable SoC is 93%, 95%, or something else. What I care about is that it's 100% of what I can charge to. In the same vein, I don't care if turtle happens at 5%, 3%, 10% or whatever. All I care is that I cannot drive any more. So show me a percentage SoC relative to what is accessible to the user. It's really the only thing that makes sense to display on the dash.

I disagree. What EVs — ALL EVs — need to show is a fuel gauge in energy units. The problem with percent is that it is relative to the current capacity of the battery. What I want to know is how far I can go and that is usable energy divided by my energy used per mile.

Getting my LEAF DD completely changed how I use my LEAF because it lets me know my SOC in Gids. When grocery shopping I know that if I have 170 Gids I can make it home, even in winter, because I have measured it. I might get home with 12 Gids in very cold weather, but I will make it.

The actual energy unit doesn't matter. I like Gids because it is a small unit (about 75 Wh). But kWh measured in tenths would suffice. And Tesla's "rated miles" is also a functional energy unit because it doesn't change with the battery capacity, it just reflects the current SOC. The actual unit used doesn't matter, just that it is consistent and predictable. Much better than a variable percent number, IMO.

 

[GRA]

This is what EVs need to start showing us. When I'm driving the car, I don't care whether the maximum allowable SoC is 93%, 95%, or something else. What I care about is that it's 100% of what I can charge to. In the same vein, I don't care if turtle happens at 5%, 3%, 10% or whatever. All I care is that I cannot drive any more. So show me a percentage SoC relative to what is accessible to the user. It's really the only thing that makes sense to display on the dash.

I disagree. What EVs — ALL EVs — need to show is a fuel gauge in energy units. The problem with percent is that it is relative to the current capacity of the battery. What I want to know is how far I can go and that is usable energy divided by my energy used per mile.

Getting my LEAF DD completely changed how I use my LEAF because it lets me know my SOC in Gids. When grocery shopping I know that if I have 170 Gids I can make it home, even in winter, because I have measured it. I might get home with 12 Gids in very cold weather, but I will make it.

The actual energy unit doesn't matter. I like Gids because it is a small unit (about 75 Wh). But kWh measured in tenths would suffice. And Tesla's "rated miles" is also a functional energy unit because it doesn't change with the battery capacity, it just reflects the current SOC. The actual unit used doesn't matter, just that it is consistent and predictable. Much better than a variable percent number, IMO.

While I agree that showing actual capacity in kWh is the best solution, the total capacity will change based on the rate of discharge, so even that's not foolproof. The way to avoid this is to have the BMS limit the capacity to one specific value, and no more regardless of how much extra capacity is available (see Chevy Volt). From the customer perspective, especially those transitioning from ICEs, this is the way to go - you shouldn't need to worry about the temp or any other factor. All you should need to know is that when you charge to full or any other %, you will have a given kWh, and that value should never change.

 

[arnis]

This graph I posted is not about degradation that happens with time.
This graph shows that other degradation that happens when juice is pumped.
(I speaked about that in my first post).

At that time I was mainly concerned with cold climate battery degradation.
This graph shows (I didn't find specific data for Leaf chemistry) that elevated
temperatures are not contributing to charging/discharging degradation.
( on the other hand age degradation speeds up with temperature).
To sum up: there are two ideal temperatures for all batteries:
Ideal operational temperature and ideal storage temperature.
Those are not the same.

Also I should mention that slow charging is not very exothermic process.
It appears that at low SOC slow charging is even endothermic (battery cools while charging).
Somewhere at about 40% that stops and then slow charging slightly heats up the chemistry.

PS! People should not really be worried with 30C/85F battery on mid-day if SOC
is "somewhere in between". 40C is not acceptable for storage (measured in days),
but is totally acceptable for operational temperature (measured in hours).

 

[dhanson865]

PS! People should not really be worried with 30C/85F battery on mid-day if SOC
is "somewhere in between". 40C is not acceptable for storage (measured in days),
but is totally acceptable for operational temperature (measured in hours).

On a leaf 40C is not acceptable at all because once you hit it even if you somehow could put the car in a 0C chamber it will take 8 hours to get the temp back down to an acceptable level.

If I garage my car at 55F/13C and drive to work 15 miles and park in an open parking lot where the temp is 20F/-7C and let it sit for 8 hours my pack is still 45F or higher when I go to drive home.

worse is the summer case

If I drive home from work with a battery at 80F/27C and let it sit in a garage at 65F/18C overnight something like 15 hours the pack will cool maybe 5F/3C. Then I drive to work 15 miles and park in an open parking lot where the air temp is 89F/32C and let it sit over asphalt the pack will rise from the prior partial cooldown to ambient in about 4 to 6 hours.

At no time in the summer would I be able to shed heat from 40C to anything reasonable. If my pack got to 40C/104F I'd have to park it in my air conditioned garage for several days to get it back to a normal temp and even then I'd see larger than normal degradation not only that first day but probably over the next few weeks.

Hitting 40C would mean it would be at upper 30s C for the next few days and then lower 30s, and then upper 20s, then if it's cooled off like maybe fall it might dip into the lower 20s. All that time it spent above 20C it's degrading faster than anybody wants it to.

Getting a leaf pack to 40C ever would be cause for alarm to me, OK I just did a bunch of gooling the forum and found someone with leafspy data that has a pack temp above 40C.

http://www.mynissanleaf.com/viewtopic.php?f=31&t=17459&start=230#p431320

2015 S with QC. Before pulling these stats I drove it on the interstate, QC'd for 15 minutes, then more interstate, then another 20 minute QC. Total drive was 85 miles. So the battery temp is quite hot. How high should I let it go before being concerned?

7/25/2014 Leafspy stats:
Location - Buford, GA
AHr = 64.38
SOH = 100% (very happy about this, but can it be true?)
Hx = 101.10%
odo = 6,298 miles
24 QCs & 149 L1/L2s
Temp F = 110.9 F avg (9.5)

110F/43C or so and man that'd concern me. There might be someone in Arizona, Texas, or Southern California that can beat that but then those are the people that ran through 4 bars in 20 months and got a free pack.

fastest to 4 bars lost

zhang000 San Jose, CA 59,996 miles 12 months VIN 001963
Scott Yarosh Phoenix, AZ 28190 miles 14 months VIN 03494
MH Phoenix, AZ unk miles, ~16 months unkown VIN
dsh Phoenix, AZ unk miles 19 months VIN 01069
gk1 Chandler, AZ 18850 miles 22.5 months VIN 05080
phxsmiley Chandler, AZ 28700 miles 23 months VIN 07837

You'll notice a close cluster in proximity with temp more important than time which is more important than miles.

 

[dgpcolorado]

While I agree that showing actual capacity in kWh is the best solution, the total capacity will change based on the rate of discharge, so even that's not foolproof. The way to avoid this is to have the BMS limit the capacity to one specific value, and no more regardless of how much extra capacity is available (see Chevy Volt). From the customer perspective, especially those transitioning from ICEs, this is the way to go - you shouldn't need to worry about the temp or any other factor. All you should need to know is that when you charge to full or any other %, you will have a given kWh, and that value should never change.

Crippling the battery, to give a consistent total kWh capacity over varying conditions and age, seems like a bizarre way to go to me. I'd like to be able to use all the battery I can, within limits of safe high and low voltages.

The whole idea of knowing total battery capacity isn't what is needed. Rather, I want an energy gauge that will tell me when I have enough to make the next leg of a trip. (The fact that the energy measurement is subject to tiny errors, due to varying measuring conditions, is essentially irrelevant; I don't cut it that close and can always adjust speed if needed. Because I am keeping an eye on the energy gauge!) I don't care what the capacity is, if it wasn't enough I wouldn't be making the trip! In the grocery shopping example I gave above, I know from measuring it that 170 Gids will get me home, doing the speed limit (to avoid annoying other drivers since there are only three brief passing lanes going uphill) at 20ºF. If I charge to at least that amount I am good to go. I've never once had to revert to "plan B" to make it home, thanks to having a reliable energy gauge.

In taking a trip in a Tesla from Salt Lake City to Price over Soldier Summit (only 7477 feet — lower than my house!) I need 118 Rated Miles in mild conditions, plus whatever small buffer I am comfortable with, perhaps 20 RM. Or about 136 rated miles at 40ºF plus the buffer. Its that simple. Nothing whatever to do with the capacity of the battery pack, so long as it is greater than needed to make the legs of the trip. If it looks as if the estimate was off, perhaps because of wind, it is a simple matter to slow down until the range remaining calculation improves.

I think it takes some years of driving electric to come to realize how best to handle the range of an EV. For early LEAFers the invention of the Gid-meter revolutionized the ability to comfortably stretch the range of the short range LEAF. In the case of the Teslas, it is more a matter of optimizing time spent driving versus charging, given that they generally have more total range than needed for most legs of a trip.

My 2¢.

 

[arnis]

Heating up and cooling down happens at the same rate if everything else stays the same.
If heat is locked in a pocket below the vehicle (heat rises cold falls down) that may change things.

For those who have garages can use regular fan just to circulate air better under the belly.
Weak 20-50W fan is all that is needed. Hardest part is to get air moving in the gap between
battery and car. Also cooling down interior should help (open window).

30C is optimal working temperature for battery. Pretty much ideal for hardcore usage.
But 40C is the upper edge for optimal working temperature, ok for use but not for rapidcharge.
30C is upper edge for storage. Nothing bad in 8hours of storage at 30C.
35C is above optimal storage and 40C is upper edge.

PS! have an idea. I believe battery service plug cover is a direct access to that air gap between car and battery.
I believe that just removing carpet and metal cover will allow MASSIVE airflow improvement.
I ask somebody to do some measurements with hot battery (no need for hot weather) :idea:
If it works then it will drastically speed up battery heat dissipation.
It is even possible to push cold AC air from cabin onto the battery upper part if vehicle is stationary and
air recirculation is disabled. Tight space between car and battery is ideal for uniform distribution of airflow (stationary).
It is safe only if there are no children inside the vehicle. But for adults it is absolutely safe. Just don't remove the fuse.
Depending on airflow this might have to be closed when driving on highway.


If this is the case I guarantee a massive change in battery cooldown period while stationary (or heatup for nordic users):
stationary in garage, windows ajar, heat rises by itself.

stationary but climate switched on (remote precool or rapid charging and waiting):

Technically that last one is active air cooling

I believe I should make another topic in this forum. This is promising. Anybody thought about that ever? Any other topics?
We shall not waste this idea if it has a slightest truth in it.

 

[dgpcolorado]

...I believe I should make another topic in this forum. This is promising. Anybody thought about that ever? Any other topics?
We shall not waste this idea if it has a slightest truth in it.

That idea has been mentioned before, although I wouldn't want to try to find where. It wouldn't surprise me if Nissan tries something like that for the much longer range LEAF 2. Unless they can come up with a chemistry that is much more heat stable than the current one (which is really poor in heat).

 

[arnis]

True, if Nissan used cabin exhaust as battery conditioner, that would change a lot.
It is possible to add short fins and have direct contact (or circulation fan inside the battery).
The upper part of battery case is always warmer than the other side.

I'll make another topic so we don't mess this up.
http://mynissanleaf.com/viewtopic.php?f=8&t=21374

 

[dhanson865]

30C is optimal working temperature for battery. Pretty much ideal for hardcore usage.
But 40C is the upper edge for optimal working temperature, ok for use but not for rapidcharge.
30C is upper edge for storage. Nothing bad in 8hours of storage at 30C.
35C is above optimal storage and 40C is upper edge.

Sorry, I don't know where you are getting these numbers from. 30C is way too hot for a Leaf pack. It might be optimal for providing power but it too high vs degradation.

Either you are looking at battery data for something other than the leaf or you are looking at theoretical data not observed data.

Real world data from actual leaf owners shows major issues with degradation at the temps you are posting about.

I personally lost 6% capacity in my pack with battery temps around 30C last summer. I don't consider losing 5% or 6% capacity in a 3-4 month period to be optimal.

I hope you don't go on repeating those numbers in other threads. I'd say your quotes on acceptable temps are misleading enough that if I saw them posted in response to another users question about degradation I'd strongly consider moderating your post. At the least I'd have to post counter to yours as a warning.

 

[GRA]

While I agree that showing actual capacity in kWh is the best solution, the total capacity will change based on the rate of discharge, so even that's not foolproof. The way to avoid this is to have the BMS limit the capacity to one specific value, and no more regardless of how much extra capacity is available (see Chevy Volt). From the customer perspective, especially those transitioning from ICEs, this is the way to go - you shouldn't need to worry about the temp or any other factor. All you should need to know is that when you charge to full or any other %, you will have a given kWh, and that value should never change.

Crippling the battery, to give a consistent total kWh capacity over varying conditions and age, seems like a bizarre way to go to me. I'd like to be able to use all the battery I can, within limits of safe high and low voltages.

Yes, Dave, but you're an early adopter, and I'm talking about mainstream users coming over from ICEs. People have been very happy with the Volt's lack of (user-detectable) degradation over the long haul, and happy customers make for lots of referral and repeat sales. GM could have used a smaller battery in the Volt and used a greater SOC range, reducing the cost of the car and lightening it somewhat. I'm very glad they took the conservative approach they did, and my only worry is whether Volt 2 will show an equal lack of user-detectable degradation over a similar period, as they've opened up the usable SOC range from 65 to 75%.

The whole idea of knowing total battery capacity isn't what is needed. Rather, I want an energy gauge that will tell me when I have enough to make the next leg of a trip. (The fact that the energy measurement is subject to tiny errors, due to varying measuring conditions, is essentially irrelevant; I don't cut it that close and can always adjust speed if needed. Because I am keeping an eye on the energy gauge!) I don't care what the capacity is, if it wasn't enough I wouldn't be making the trip! In the grocery shopping example I gave above, I know from measuring it that 170 Gids will get me home, doing the speed limit (to avoid annoying other drivers since there are only three brief passing lanes going uphill) at 20ºF. If I charge to at least that amount I am good to go. I've never once had to revert to "plan B" to make it home, thanks to having a reliable energy gauge.

In taking a trip in a Tesla from Salt Lake City to Price over Soldier Summit (only 7477 feet — lower than my house!) I need 118 Rated Miles in mild conditions, plus whatever small buffer I am comfortable with, perhaps 20 RM. Or about 136 rated miles at 40ºF plus the buffer. Its that simple. Nothing whatever to do with the capacity of the battery pack, so long as it is greater than needed to make the legs of the trip. If it looks as if the estimate was off, perhaps because of wind, it is a simple matter to slow down until the range remaining calculation improves.

ISTM that works with any reasonably accurate energy gauge, no matter what it's calibrated in. Once the charging infrastructure is ubiquitous, you won't need such a precise gauge, and something akin to the typical gas gauge will be plenty accurate.

I think it takes some years of driving electric to come to realize how best to handle the range of an EV. For early LEAFers the invention of the Gid-meter revolutionized the ability to comfortably stretch the range of the short range LEAF. In the case of the Teslas, it is more a matter of optimizing time spent driving versus charging, given that they generally have more total range than needed for most legs of a trip.

My 2¢.

I think Tesla people are operating in the manner you suggest, because the SC charge rates are always high enough that it's worthwhile to drive as fast as you want and then stop. There's no need for the elaborate calcs necessary for a car like a LEAF with a much lower charge rate.

 

[arnis]

Sorry, I don't know where you are getting these numbers from. 30C is way too hot for a Leaf pack. It might be optimal for providing power but it too high vs degradation.

Either you are looking at battery data for something other than the leaf or you are looking at theoretical data not observed data.

Real world data from actual leaf owners shows major issues with degradation at the temps you are posting about.

First of all don't put all Leaf batteries in one basket. I should mention again, that the newer
version is much more capable withstanding higher temperatures.

And nr2: Are you referring to operational temperature or ambient?
Average battery temperature tends to be up to 10C above ambient without rapid charges.
As I read real problems are in places like Phoenix:

Taking that average as ambient for many (no AC garages), 90F is 32C.
Like I mentioned 30C might be good for use, but it is not optimal for storage.
And 90F storage is already above that. As Leaf is being used every day
I suspect temp can easily go up to 40C. In shade. Because average temperature
is air at some height above the ground. Most Leaf are not white inside out.
And solar loading will not let battery (5-10C above ambient) to cool down.
Here were I live we often have cloudy weather and battery starts cooling down
few hours after driving. Temperature at 7am is often same at 3pm. This is why I
clearly see that temperature change.

And as you quoted me, 35C is above optimal storage and 40C is upper edge.
Upper edge vs optimal upper edge - sorry, I used that incorrectly. I'll rephrase:
30C is optimal working temperature
40C is maximum optimal working temperature

30C is maximum optimal storage temperature
35C is above optimal storage and 40C is upper edge (imagine thermometer with last dash value 40C)



Those two different limits (one for storage other for cycling) must be obeyed simultaneously if car is not stationary
(and stationary means that SOC is 30-60% no cycling 24/7). If first limit is exceeded (storage limit) then there is
degradation that happens because of that (let's call that S-degradation). And if the other limit is exceeded then
degradation that happens because juice is cycled in and out (let's call that C-degradation). In this case if C temp
is exceeded S temp is heavily exceeded.

It is important to know the difference because dominant degradation that happens when battery is cold is C-type.
Dominant degradation that happens with hot batteries is S-type.
Therefore using Leaf nonstop with chemistry at fixed 40C is more reasonable than not using heavily.

On the other side 3 years at -15C is OK but any usage at -15C makes things much worse (C lower limit exceeded).
At fixed -15C a lot of C-degradation happens. Luckily there is a heater that won't let the worst to happen.

Here in Estonia we have moderate summers with 20C day/night average. We do have Leafs that are
super heavily used. Battery can heat up to 9-10 bars easily. But there is not a lot of degradation. And those are
first generation Leafs with old battery. Why? Because S-degradation is not speeding up with heavy usage.
Those Leafs always cool down very rapidly in our weather (delta T is huge, especially at night). 1 week in Phoenix
(24x7=168h) is like one whole summer of heavy usage here.

Numbers I write are not black and white (those are not hard limits). And they are definitely not specifically for 2011-2012 batteries.
Also it is hard for me to believe that there is a big fleet of users who always monitor their battery temperature with LeafSpy.
Those summaries that are available (lost 1-2-3-4-5 bar list for example) also show many who have lost slightly above normal
capacity. It shows that different scenarios give different results (like heavy acceleration or parking in shade).
I would like to see more data with average cell temperature, SOC and DoD behavior rather than just mileage and hometown.

Like I mentioned above heavy discharge has more effect and is heavily exothermic. Maybe it has more effect than we used to think.

 

[GetOffYourGas]

Heating up and cooling down happens at the same rate if everything else stays the same.
If heat is locked in a pocket below the vehicle (heat rises cold falls down) that may change things.

For those who have garages can use regular fan just to circulate air better under the belly.
Weak 20-50W fan is all that is needed. Hardest part is to get air moving in the gap between
battery and car. Also cooling down interior should help (open window).

30C is optimal working temperature for battery. Pretty much ideal for hardcore usage.
But 40C is the upper edge for optimal working temperature, ok for use but not for rapidcharge.
30C is upper edge for storage. Nothing bad in 8hours of storage at 30C.
35C is above optimal storage and 40C is upper edge.

PS! have an idea. I believe battery service plug cover is a direct access to that air gap between car and battery.
I believe that just removing carpet and metal cover will allow MASSIVE airflow improvement.
I ask somebody to do some measurements with hot battery (no need for hot weather) :idea:
If it works then it will drastically speed up battery heat dissipation.
It is even possible to push cold AC air from cabin onto the battery upper part if vehicle is stationary and
air recirculation is disabled. Tight space between car and battery is ideal for uniform distribution of airflow (stationary).
It is safe only if there are no children inside the vehicle. But for adults it is absolutely safe. Just don't remove the fuse.
Depending on airflow this might have to be closed when driving on highway.


If this is the case I guarantee a massive change in battery cooldown period while stationary (or heatup for nordic users):
stationary in garage, windows ajar, heat rises by itself.

stationary but climate switched on (remote precool or rapid charging and waiting):

Technically that last one is active air cooling

I believe I should make another topic in this forum. This is promising. Anybody thought about that ever? Any other topics?
We shall not waste this idea if it has a slightest truth in it.

Arnis, you seem to be well educated, and have provided lots of useful information. However, you repeatedly state that "heat rises" which, in itself, is untrue. Heat only "rises" in one form of heat transfer - convection. It is rising because most fluids (liquids and gasses) are less dense when they are warmer. So it's actually the warmer fluid that is rising, carrying the heat with it. A notable exception is water from 0-4C; it is weird in many regards.

There are two other methods of heat transfer: conduction and radiation. When we are talking about cooling the envelope of the Leaf's battery - which AFAIK is in a sealed container - we are mostly talking about these two methods of heat transfer. And neither one follows the "heat rises" convention. They simply flow from a hotter object to a cooler one, regardless of gravitational forces.

The implication of all of this is that just as much heat can be drawn off the bottom of the battery container as from the top. This may actually be more effective, if someone were to install cooling fins under the car that air could flow over. Of course, once you park over hot asphalt, the reverse will be true, and the battery will warm up faster.

 

[dhanson865]

First of all don't put all Leaf batteries in one basket. I should mention again, that the newer
version is much more capable withstanding higher temperatures.

and again for the 100th time I'll tell you what I've told others. The 2013 and 2015 battery pack reversions have almost no noticeable improvement for Leaf users in the southern US.

To call it "much more capable withstanding higher temperatures" is a falsehood of a high order.

You seriously need to do more reading on this forum and less writing. You have a lot to learn about degradation due to heat.

See http://www.mynissanleaf.com/viewtopic.php?f=27&t=20706 for 2015 packs degrading just as bad as 2011 packs.

See http://www.mynissanleaf.com/viewtopic.php?t=18269 for 2013 packs doing not much better than 2011 packs.

See http://www.mynissanleaf.com/viewtopic.php?f=30&t=8802 for the monster 700+ page thread that started it all including the trials and tribulations of leaf owners trying fans and other cooling methods that didn't work.

See Stoatys model http://www.mynissanleaf.com/viewtopic.php?t=14858 and dig into the spreadsheet math if you like

See http://www.mynissanleaf.com/wiki/index.php?title=Real_World_Battery_Capacity_Loss for a list of cars that lost battery capacity tallied all in one place

Please do a lot of reading and accept that you don't know enough to be writing the replies you've been writing in this thread. Please refrain from further posts until you've gained an understanding of the heat data and work that those before you have put in.