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Comment by sengstrom | Hacker News Reader

I wonder if using the supercharger deteriorates the battery more than a more gentle charge (I am warned about this for fast charging my Leaf). Find it interesting that they ask that question on the supercharger FAQ but don't answer it:

"How often can I Supercharge? Is it bad for my battery? Supercharging does not alter the new vehicle warranty. Customers are free to use the network as much as they like."

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Charging the battery fast isn't necessarily so bad in and of itself, but fast charging tends to generate a lot of heat, and high heat is bad for lithium ion longevity. The Model S has a battery cooling system built into the car which kicks on when needed, so this is not such a big issue.

The Leaf doesn't have any battery chillers though, so fast charging may indeed be bad for it. Also, even though most DC fast chargers only put out 50kW (as opposed to 120kW for Superchargers), if you consider how much smaller the Leaf pack is, you're actually charging the battery faster than a Supercharger can charge a Tesla.

That said, this study seems to indicate that fast charging isn't all that bad for Leafs anyway: http://insideevs.com/idaho-national-laboratory-dc-quick-char...

I am not a battery scientist, but from everything I've read, using the supercharger should have no effect on battery life long-term. So long as it's kept within certain charge and temperature ranges, the only thing that counts down the lifetime of the battery cells are actual charge cycles, which you can pretty conveniently measure in miles of normal driving use (expected up to 30% loss after 100K miles, and the 5+ year old Roadsters actually averaged just 15% loss after 100K miles with older battery tech). The supercharger doesn't do anything that would reduce that life expectancy; it communicates with the battery about its health and charging speed begins to slow progressively after about 50%.

Not really true, there's many variables including how 'full' you charge the battery, how much you discharge it, what the charge and run temps are, it's not a simple equation.

For example, if you don't charge and discharge the battery fully, you can get many many times more cycles out of them.

Charging quickly does release more heat, which can reduce the lifecycle of the battery, but there are workarounds to minimize this.

I am not an expert at battery chemistries, but I work with EV charging systems quite a bit.

> Charging quickly does release more heat, which can reduce the lifecycle of the battery, but there are workarounds to minimize this.

I suspect that's why the GP was warned not to quick-charge his/her Leaf too often: The Leaf battery does not have an active cooling system.

What part is "not really true"? Despite only writing three sentences, I touched on every factor you just mentioned. The Tesla charger and battery system keep the battery within the safe charge and temperature ranges at all times, even when supercharging. It has active heating and cooling, even when the car is turned off, and will neither fully discharge nor fully charge the battery pack even if left unattended. There's nothing inherently damaging about temporarily charging faster AFAIK as long as you control for all those variables, which Tesla's tech does.

It must damage the battery somehow. If it didn't, Tesla would have said so in the FAQ, instead of trying to sidestep the question.

Truth is, the type of use these batteries get isn't well understood yet. No one really knows the long term effects, we can make educated guesses but until a lot of them are in the field with average use cases for years, we won't see much of the nuance.

Sorry, I was referring specifically to your statement: "the only thing that counts down the lifetime of the battery cells are actual charge cycles"

That was immediately preceded with the qualifier, "So long as it's kept within certain charge and temperature ranges...."

Which are two of the very many variables. His point that a certain number of cycles is consistent is not correct, it's affected by drive and charge style, and a lot of variable inherent in the design of the system.

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