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Nissan Leaf
- Thread starter efusco
- Start date
The focused, technical response to the (my interpretation) "flippant" use of "air cooled brain".
Kipernicus
Model S Res#P1440
DuncanWatson
Member
Tony,
I agree with you. They have painted themselves into a corner. I am waiting to see if they come out with anything that works for the SE US. I don't think their current proposal will be enough. Nissan is the only company that is even close to Tesla. They have a lead on the others but this issue may squander that lead. I do wish them well and hope a 48Kwh version of the Leaf comes out with a 160+ mile range and CHAdeMO L3 charging.
But the heat issue may kill them. The world isn't getting any cooler.
darthvdr
Member
There's one particularly vocal Leaf owner at my work here in San Diego who has basically had to stop driving his car, because it will no longer reliably get him to work and back. San Diego actually has a fairly mild climate compared to much of SoCal. Anyway, it's another data point.
This is the main reason why I jumped from 40kWh to 85kWh. I was worried about my normal driving about 5 years from now. I would be doing 80% of the 'standard charge' a couple times a week.
TonyWilliams
Active Member
We've come a long way from last September 2012 when Nissan was publically stating from the highest levels of the company that the batteries were all fine, and we LEAF owners didn't know what we were talking about (and any problems we thought we observed were merely the instruments).
Now, they're actively working on the "heat resistant" battery and the former LEAF manager is "retired" from Nissan (at age 55 while directly in the middle of this potentially LEAF ending issue).
I'd like to think we at least started to turn the ship around on Sept 15, 2012... Nissan did pay for all our testing costs post facto:
All The Results From Independent Test Of Nissan LEAFs With Lost Capacity. Not All Instrument Failure
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Just to jump in. The TMS on a Tesla doesn't kick in until over 100 degrees. It may just be that a TMS isn't needed in most climates if they aren't charged quickly.
The most cost effective option would be an optional TMS. Obviously, Phoenix and FL need something regardless of battery chemistry. Lots of So Cal too. But I live in the SE US but I don't experience anything like Phoenix. Over 100 wasn't seen this summer and is on average seen 5 days a year and then probably for 2 hours total. So I don't see what Tesla's TMS would have done unless I was supercharging or QCing (which I don't do).
While the Leaf isn't actively air cooled (you have to agree that active/passive brings some clarity to the issue), most of the time it gets to ambient eventually but has a pretty significant latency b/c of significant mass. It also doesn't get that much higher than ambient if you don't QC.
I do think that using the a/c pump already there to run some cool air over the battery in high temps or during QCing makes a lot of sense.
Lastly, while the battery isn't actively air cooled, I do hear pumps running when I charge at 20 amps that I don't hear when charging at 10 amps.
The most cost effective option would be an optional TMS. Obviously, Phoenix and FL need something regardless of battery chemistry. Lots of So Cal too. But I live in the SE US but I don't experience anything like Phoenix. Over 100 wasn't seen this summer and is on average seen 5 days a year and then probably for 2 hours total. So I don't see what Tesla's TMS would have done unless I was supercharging or QCing (which I don't do).
While the Leaf isn't actively air cooled (you have to agree that active/passive brings some clarity to the issue), most of the time it gets to ambient eventually but has a pretty significant latency b/c of significant mass. It also doesn't get that much higher than ambient if you don't QC.
I do think that using the a/c pump already there to run some cool air over the battery in high temps or during QCing makes a lot of sense.
Lastly, while the battery isn't actively air cooled, I do hear pumps running when I charge at 20 amps that I don't hear when charging at 10 amps.
stopcrazypp
Well-Known Member
Depends on the chemistry of the battery. My LEAFs battery has probably only seen north of 100F a couple times and for short periods of time. Yet after 2.5 years capacity is down about 15% despite living in a very moderate climate. Tesla cooled the Roadster's battery pack more aggressively and GM cools the Volt's battery more aggressively, too. But even with cooling, I suspect the LEAF would still see faster than expected capacity loss because Nissan chose not to use an expensive separator in their battery. They are reportedly testing a battery with a tougher separator which is supposed to start production first half of next year if testing goes well - this is the "hot" battery which Nissan has referenced before and supposedly has twice the heat durability of the current battery. Even then, I don't think it will be enough for areas like Phoenix or Palm Springs.
My LEAF's battery seems to stay around 5 F over ambient during the day. A 20-25min QC will raise pack temps by 10-12F typically.
Is this on a LEAF or Model S you are referring to? Probably the OBC as stopcrazypp mentions, but at least on my '11, the cooling pumps run regardless of charge rate.
stopcrazypp
Well-Known Member
There's a small nuance to that point about the 100F too: that specification is only for when the car is off. The TMS is definitely on when the Model S is on.
I heard about that too. I was quite surprised they skimped on the separator. The cathode chemistry itself (lithium manganese) is more thermally stable so everyone expected the batteries to do fine in hot climates (esp. given Nissan PR was so confident early on). Hopefully the new separator addresses most of the problem, but a TMS would be the thing that guarantees it's not a problem. Even though the Spark is a compliance car and uses a cell that has been tested to do fine in high temperatures (a123), GM still went with a liquid cooling system for the battery. It's just something that shouldn't be skipped.
I live in Texas where it's 95 or above July through September, so if I had a LEAF then I would see battery loss just because of the high temps or is it high temps plus charging?
All this info is great to learn for when I'm ready to buy an EV. Thanks! The LEAF is my backup if I can't afford the GEN III, hopefully Nissan will have extremely improved the battery situation by then.
All this info is great to learn for when I'm ready to buy an EV. Thanks! The LEAF is my backup if I can't afford the GEN III, hopefully Nissan will have extremely improved the battery situation by then.
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There are two factors that lead to battery capacity loss. All lithium batteries suffer from this to some degree and some more than others.
1. Calendar life losses. Lithium batteries will lose capacity just sitting there. The two primary factors that affect the rate of calendar life loss are temperature and state-of-charge. Approximately for every 10C increase you double the rate of capacity loss, see Arrhenius' Equation. In general, optimal state of charge for storage is between 30-50% charged with high states of charge being the worst. It generally starts to spike as you get above 80-90% SOC depending on the battery.
2. Cycle life losses. Lithium batteries will lose capacity after charge/discharge cycles. In general, shallow, gentle cycles around 50% SOC is easiest on the battery. Full cycles (100% to 0% and back) are the hardest. One reason is because lithium batteries expand slightly when charged and shrink slightly when discharged. Again, the effects of this are largest at very low SOC and very high SOC. One might think that 2 75%-25% discharge/charge cycles are the same as one 100%-0% discharge/charge cycle, but because the battery doesn't undergo the stresses of being fully charged or discharged, a battery will suffer much less damage after 2 50% cycles than 1 full cycle.
Yep. It is.
The whole PDM stack on my '13 :Leaf gets quite warm after many hours of charging. And, I can feel what's almost certainly circulation through the hoses when the pumps are running.
I knew the battery lost capacity over the years from the number of cycles, but from reading the past several posts, didn't know if getting one in Texas would be a good thing if it can't do well in extreme heat. I know other Texans have them, I even see one driving the same way to work in the morning, but I'm glad I'm on these boards learning the ins and outs. Thanks for the detailed information, that was great to learn.
A lease is your friend in hot climates with the LEAF, especially a 2 year lease. By the time the lease is over Nissan had better get the fast capacity loss in hot climates under control, otherwise their whole EV program will be in jeopardy.
It will be very interesting to see if Model S packs hold up as well as Roadster packs have, the Roadster is really the benchmark to beat when looking at capacity loss over time/miles.
So the 2013 runs fans only when charging at high amperage. I have an adjustable EVSE and when I set at 10 amps, I don't hear the fans.
While the TMS runs on the Tesla at lower temps when the car is running, the vast majority of life is spent sitting. Since that is the calendar life temp issue, cooling more when the car is running barely helps for that. It certainly allows and helps for spirited driving but for calendar life degradation, it isn't bad.
Losing 15% at 2 years isn't horrible especially since the degradation should plateau. No question the Model S seems to be a longer lasting battery but I suspect most of that is not related to TMS but more to battery design. Everyone likes to blame the TMS but I think the issue is not that simple.
It should be noted that the NREL study showed that 50-25% cycle is better for the battery than 75-50%. I believe they even found that 50-0% was better than 75-25% despite what everyone says about very low SOCs.
While the TMS runs on the Tesla at lower temps when the car is running, the vast majority of life is spent sitting. Since that is the calendar life temp issue, cooling more when the car is running barely helps for that. It certainly allows and helps for spirited driving but for calendar life degradation, it isn't bad.
Losing 15% at 2 years isn't horrible especially since the degradation should plateau. No question the Model S seems to be a longer lasting battery but I suspect most of that is not related to TMS but more to battery design. Everyone likes to blame the TMS but I think the issue is not that simple.
It should be noted that the NREL study showed that 50-25% cycle is better for the battery than 75-50%. I believe they even found that 50-0% was better than 75-25% despite what everyone says about very low SOCs.
I agree - I think it's the battery itself more than the lack of TMS given the rate of capacity loss even in pretty mild weather areas.
Yes, I recall seeing the same study/data - basically the battery lasts longer because the average SOC is lower. I would love to see similar tests on batteries used in today's EVs and PHEVs.
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