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Comment by Robotbeat | Hacker News Reader

Yes, it would, but that’s part of making the overall car and it depends on lifetime. As EV batteries can now last 500,000 miles (vs 250,000 miles for first generation long range EVs), that’s not as big of an impact as many assume. (A lot of papers assume really low EV lifetimes, like just 100,000 miles, and no secondary reuse of the battery and they assume really outdated and inefficient numbers for manufacturing the cells.)

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Only tangentially related, but I wonder what the expected battery lifetime drops to when you factor in crashes. You mention that the cells might last 500,000 miles but is that really relevant if you're likely to have your car totaled before 200,000?

Are there diminishing returns if you are a company working on a million mile battery since virtually no vehicles will make it that far?

I am speaking as someone who has had three cars totaled before 100,000 miles (none of which were my fault!)

I imagine most of the longevity research is actually being done for the stationary battery market.

The fact it carries over to vehicles is just a bonus.

Besides the salvage value of a battery pack would be huge, so I suspect a battery would be about the last piece of a car to end up on the scrap heap.

The point is that the worst quality studies do assume that the battery ends up on the scrap heap, way before the car itself does.

Totaled EVs are a great source of second-hand battery modules, used either for fixing broken batteries or even for grid storage.

Lots of commercial vehicles make it to a million miles. Those are the ones that will want the longest lived batteries.

> You mention that the cells might last 500,000 miles but is that really relevant if you're likely to have your car totaled

The market for batteries pulled from wrecks is hot! For my own personal interest I wish it wasn't so I could batteries for cheap.

Why are batteries typically measured in miles, rather than years and or recharges? Age and charge cycles are the two hardest things on batteries, not distance traveled. I for example will not drive 500k in my life, but I'm sure the battery is going to have much less capacity and life left in 10 to 20 years regardless.

It depends on what you are talking about. If you are talking about a battery car, then it is better to use a number that makes sense for the end user, and number of charge cycle is not an easy one. If you recharge from 70% to 90% every day, is that a cycle, is that 1/5th of a cycle?

The main problem is the number of full capacity cycling a battery cell can do can change widely based in how it is used. So it depends on how it is integrated into a car and how the car is being used. A typical Li-Ion cell will last a few hundred cycles if cycled completely at a high rate without proper thermal control. But this number can easily be multiplied by 10 with proper thermal management, not charging it to max voltage and doing shallower cycling. If you want to give a number for a final product, you are bound to make assumptions on how it will be used. And at this point you just have an equivalence between distance driven and cycling count.

Also, age has less impact than cycling count in the context of a properly designed battery pack. The two main factors for battery degradation are time spent at high temperature and high state of charge, and cycling count (with speed and depth being the key elements). EV manufacturers are keeping a buffer for that purpose and their batteries do not spend a lot of time at high state of charge where the chemical degradation is more effective.

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