Battery temp management for new leaf

[johnlocke]

All Leaf's rely on convection cooling of the sealed battery pack. Most of that is provided by airflow across the bottom of the battery. Although the battery does bolt onto the chassis there are no thermal pads to provide a heat path to the chassis and the bolt pads provide only a small contact area for heat transfer. It is safe to say that the major cooling effect is by convection and is only effective when the car is moving.

Nissan sealed the battery packs to prevent corrosion and contain any battery fluid leaks. Their cooling solution is adequate for the British Isles and Europe. It even works in the northern half of the U.S. for the most part. It is not suitable for the southern half of of the U.S.

[edatoakrun]

You have packed quite a bit of misinformation in your post below.

Next time you park your LEAF with the battery temperature significantly above ambient, watch the rate at which the pack temperature declines to see for yourself that this statement is false.

All Leaf's rely on convection cooling of the sealed battery pack. Most of that is provided by airflow across the bottom of the battery. Although the battery does bolt onto the chassis there are no thermal pads to provide a heat path to the chassis and the bolt pads provide only a small contact area for heat transfer. It is safe to say that the major cooling effect is by convection and is only effective when the car is moving.

Nissan sealed the battery packs to prevent corrosion and contain any battery fluid leaks. Their cooling solution is adequate for the British Isles and Europe. It even works in the northern half of the U.S. for the most part. It is not suitable for the southern half of of the U.S.

Why do those who have such serious anxiety regarding battery temperatures in passively manged packs keep buying LEAFs, and continue sharing their insecurities on this forum?

[johnlocke]

You have packed quite a bit of misinformation in your post below.

Next time you park your LEAF with the battery temperature significantly above ambient, watch the rate at which the pack temperature declines to see for yourself that this statement is false.

All Leaf's rely on convection cooling of the sealed battery pack. Most of that is provided by airflow across the bottom of the battery. Although the battery does bolt onto the chassis there are no thermal pads to provide a heat path to the chassis and the bolt pads provide only a small contact area for heat transfer. It is safe to say that the major cooling effect is by convection and is only effective when the car is moving.

Nissan sealed the battery packs to prevent corrosion and contain any battery fluid leaks. Their cooling solution is adequate for the British Isles and Europe. It even works in the northern half of the U.S. for the most part. It is not suitable for the southern half of of the U.S.

Why do those who have such serious anxiety regarding battery temperatures in passively manged packs keep buying LEAFs, and continue sharing their insecurities on this forum?

When you burn your finger, do you blow on it to cool it off or do you hold it still in stagnant air? The battery takes literally hours to cool when sitting still overnight even when the temps are significantly lower. While there is some cooling effect in stagnant air, convection cooling works best when there is moving air. That's why your computer has fans inside. To move air around and exhaust heated air from the system.

As to why I bought a Leaf, it was the only electric car I could afford that met my needs. Really would have liked to get a Tesla S but $70K is out of my price range. As to why I complain, I have a 22 mo. old car with 35,000 mi on it and only 73% of its original capacity! I thought that Nissan had solved their battery problems since they were offering a 100,000 mi. warranty. Rest assured that I won't be buying another car with a passively cooled battery. I bought this car with the intention of driving it for 150,000 mi +. That's probably not going to happen. Even if I get a couple of replacement batteries out of Nissan, at the rate of degradation I'm seeing currently the third battery will be shot at 120K and the resale value will be zilch.

[Oils4AsphaultOnly]

Why do those who have such serious anxiety regarding battery temperatures in passively manged packs keep buying LEAFs, and continue sharing their insecurities on this forum?

Because the leaf was what I could afford too! And Nissan never said that the leaf wasn't appropriate for my area either. Their local radio ad made no mention of this restriction either! As a matter of fact, my local dealer had 7 on hand when I was deciding whether or not to get mine.

It's one of those lessons some of us has had to learn firsthand, as it wasn't common knowledge.

[GerryAZ]

Passive battery cooling is the best option for my usage pattern so I accept some deterioration over time. I will not buy an EV that has battery chemistry which requires active cooling even when parked. My 2015 LEAF is doing much better than the 2011 (both original and replacement batteries). I am disappointed to hear of so many 30 kWh batteries in milder climates losing capacity bars at low mileage. My 2015 with original battery has 48,653 miles and 11 capacity bars right now as I am using the third QC in the past 8 hours. It is clear that I will be far beyond the capacity warranty end at 60,000 miles before it is down to 8 bars (unless capacity starts dropping rapidly).

[DaveinOlyWA]

Passive battery cooling is the best option for my usage pattern so I accept some deterioration over time. I will not buy an EV that has battery chemistry which requires active cooling even when parked. My 2015 LEAF is doing much better than the 2011 (both original and replacement batteries). I am disappointed to hear of so many 30 kWh batteries in milder climates losing capacity bars at low mileage. My 2015 with original battery has 48,653 miles and 11 capacity bars right now as I am using the third QC in the past 8 hours. It is clear that I will be far beyond the capacity warranty end at 60,000 miles before it is down to 8 bars (unless capacity starts dropping rapidly).

It does suck that early 30 kwh packs are likely part of a batch that is defective but the degradation is so rapid, all will easily qualify for a replacement. Remember its now 100,000 miles and by the looks of it, people in the North will hit that before 60,000 while people in the South will hit it before 40,000 (some MUCH earlier)

In reality, its turning into a slow recall since all the affected packs will be replaced eventually.

[powersurge]

I think all this worry and complaint about battery cooling and deterioration is all a myth that some are using to either discredit the Nissan company or for Nissan to blame battery deterioration on temperature rather than time. If all members recall their past experience, they may see my point.

Except for those hot climates where daily temperatures are over 100 degrees, the reported posts on battery temperature are irrelevant. If posters are complaining that their battery temperatures have "spiked" up to 100 or even 112 degrees, their complaints are totally trivial. First, if you are driving in a 70-95 degree ambient temperature (and the car's battery is working hard to propel you at high speed), what is so terrible if the battery temperature goes up to 100-110 degrees? That temperature is just slightly above your normal body temperature. If you touch something with that temperature, then you would hardly perceive that it is hot at all... Maybe a bit warm. I cannot imagine that that temperature would DEGRADE any rechargeable battery. Man, my Samsung cell phone gets so hot that it burns in my pocket at times, and it still continues to work fine for years. In my opinion, battery temps of 120-140 degrees would be more damaging than at 100 degrees.

Second, this is my theory of what is happening. I have used rechargeable batteries since the 1970s in all types of products, and the following NEVER changes. Rechargeable batteries do an amazing job of holding and giving out electricity, with many cycles of discharge and charging. Truth is that rechargeable batteries have still not progressed that much. The lifetime of a cordless drill battery (my closest comparable battery to EV batteries) only last 2-4 years before they do not hold a charge.

So, it is my "conspiracy theory" belief that (except the crazy people that buy Leafs and live in desert and tropical climates) all battery deterioration that people report is a NORMAL expression of the battery's normal lifetime. Think of it, my battery has over 1500 charging cycles and is still (for now) strong. THAT is amazing. Of course, Nissan would never "to your face" tell you that their batteries are strong for only 2-3 years and go downhill from there. No one would ever consciously buy their cars then. SO.... It is easier to blame high battery temperatures (caused by users), which give us users the "fantasy" that we can extend the life of our cars with careful use. Its like the TV commercial fantasy that if you eat probiotics and organic food, you will live to 120...

I, personally, voluntarily took the plunge with my Leaf and hope that by the time my battery needs to be excised, batteries will either last longer or will have greater capacity. I really think that Leaf owners should consider themselves as trailblazers who are testing out the future technology of our planet. They should not be considering themselves as "discriminating consumers" that EXPECT all their products should work perfectly, like their continued fantasy that their world should be also perfect.

[SageBrush]

Why do those who have such serious anxiety regarding battery temperatures in passively manged packs keep buying LEAFs, and continue sharing their insecurities on this forum?

Not insecurities, disappointment with how fast the battery is aging.

Should they have known how crappy the battery is before purchase ?
Perhaps, but now they are doing their part to save others from the same fate. You know, to reduce your annoyance.

[WetEV]

Arrhenius's law.

Batteries have unwanted side reactions that degrade the chemistry of the cell. Roughly every 10C the rate of these reactions will double. So if your battery gets 10C warmer for a day, then it degrades as much as two normal days in your climate. Or if you are American, 14F warmer.

My battery this time of the year is often near 15C. I've recently taken some long trips, with multiple DCQCs, and once got my battery to 38.4C. That one day aged my battery about as much as four normal days, as was roughly 20C warmer. Actually probably more than that, as quick charge also degrades batteries faster, even at the same temperature. My previous record battery temperature was 32C, and that was in summer.

So does it matter? Yes, but not very much unless you do this a lot. As I've started to take trips like this more frequently, I'm no longer in contention for the 100k miles on a 24kWh battery before losing the first bar competition. Oh, and I'm not disappointed in how fast my battery is aging. The battery isn't "crappy", but isn't the best choice for vary hot places.

[DaveinOlyWA]

Why do those who have such serious anxiety regarding battery temperatures in passively manged packs keep buying LEAFs, and continue sharing their insecurities on this forum?

Sorry but haven't the slightest idea what you are talking about.

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