Hacker News Reader

Comment by Matterless | Hacker News Reader

/Up to 1000 charge cycles/ is a big damper on the excitement, for me. Does anyone know if a limitation like that is inherent to the chemistry here or is this something that they could potentially (hopefully, vastly) surpass?

View on HN

That's a comparable rating to the NMC Lithium cells used in an electric car, yet an EV can typically get > 200,000 miles from their cells. A charge cycle is defined as 0% -> 100% -> 0%. If you never do that, you get a lot more effective charge cycles.

Edit:

That's not the full explanation. 300 miles of range for a typical EV * 1000 cycle rating gives 300,000 mile rating.

You likely charge a lot more than 1000 times over those 300,000 miles, but a partial charge counts as a partial cycle.

To add on to that, battery "lifetime" is typically defined as 80% of original capacity. So after 1000 full cycles, you still have 80% capacity left!

It should be said that at that point you don’t have very many charge cycles left after the capacity drops below 80%, and the capacity will drop a lot faster for every charge cycle after that point.

I don’t have exact numbers.. based on graphs I’ve seen I would guess that if the original cycle life was 1000 cycles you may have another 500 cycles until the battery is actually unusable. But it probably depends a lot on the specific chemistry and how the car is used.

If 1000 cycles is 250,000 miles, then an additional 500 cycles also seems like a large number.

A study[1] was recently posted[2] which found that for lithium-ion batteries, dynamic use lead to much better battery life compared to fixed-current discharges which is typically used in labs to determine battery life.

From the paper: Specifically, for the same average current and voltage window, varying the dynamic discharge profile led to an increase of up to 38% in equivalent full cycles at end of life.

This tracks well with actual real-world data on BEV battery performance in cars with decent battery management.

[1]: https://www.nature.com/articles/s41560-024-01675-8

[2]: https://news.ycombinator.com/item?id=42370438

If an EV goes 400 miles on a single charge, then you're looking at 400000 miles of total range! That's absolutely acceptable.

And at more than double the energy density of today's EV batteries, its range could be considerably longer.

Up to 500 cycles is the textbook figure for Li-ion cells. Actual performances vary, that's not an indicator of a major problem in the technology.

Reply on news.ycombinator.com