Capacity Loss on 2011-2012 LEAFs

[Stoaty]

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. ... What_To_Do" onclick="window.open(this.href);return false;

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

[siai]

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 ) 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.

[Herm]

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.

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.

[Herm]

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.

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.

[Stoaty]

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.

Reference or link?

[Boomer23]

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.

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.

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

[opossum]

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.

[shrink]

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.

LOL.



Is he terminating his lease?

[opossum]

He is.

[TonyWilliams]

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

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