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Would this be a correct summary of the paper? 1) eliminates Cobalt 2) improves energy density (more range) 3) faster charge rate 4) less SOC (state of charg

Would this be a correct summary of the paper? 1) eliminates Cobalt 2) improves energy density (more range) 3) faster charge rate 4) less SOC (state of charge) swing, meaning less cost & weight 4) 5x longer lifespan

alanh 7y ago
what is 'state of charge swing'?
- hwillis 7y ago
  I think it is referring to the fact that it is ubiquitous to leave some amount of reserve so that the battery is never fully charged (100% SoC) or discharged (0% SoC). This formulation is capable of going the full 0-100%, while most formulations will last significantly longer if they don't do that.[1] In that graph, charging to 75% and discharging to 25% gives you about 3x more life than from 25%-100%. NB that most li-ion cells are rated for 300-1000 cycles at 100% Depth of Discharge. Reducing the DoD to 90% or 80% will get you thousands or tens of thousands of cycles, although it is abnormal to actually measure that long. A charge-discharge cycle at .1 C (the former standard) takes 20 hours. [1]: https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg https://batteryuniversity.com/_img/content/DST-cycles-web2.j...
  - FooHentai 7y ago
    24kw leaf battery is an example of this with user stats seemingly bearing it out. Charge it to 80% each time, you can expect 3000 cycles before it's spent (drops below 85% of original capacity). If you charge to 100% each time, you'll only get 1000 cycles. 3-4 years versus 8-10 years use makes a big difference.
    - taneq 7y ago
      The 85% capacity benchmark seems pretty arbitrary to me. I'd imagine most owners very rarely use more than 85% of their range (or at least, could avoid doing so easily) at which point 85% isn't "needs expensive battery replacement", it's just "slightly less range buffer". I imagine in 20 years' time we'll see plenty of old beaters, student cars etc. with 50% or less range that are still quite happily driving around.
      - drcross 7y ago
        That's already the case, you can pick up 2013 Nissan Leafs with very small batteries for small money. They're used for commute cars or grocery pickup.
hwillis 7y ago
1) 532 is not a new chemistry. It's not even the lowest cobalt chemistry; there's 511 and 811 beyond that (811, or 80% nickel, 10% manganese, and 10% cobalt, is not yet technically feasible). 2) Range is decreased. 532 has lower energy density. 3) Maybe..? But nothing truly significant. The additives in this chemistry mean a lot of heat gets generated during charge/discharge. Heat is the limiting factor during charge, so swapping directly to this would mean lower top charging speed. However with better cooling... maybe? It can sustain high charge current for longer, but not as high overall. 4) The buffer for EVs is ~10%. It's not a big factor in cost or weight. 5) Yes, 5x longer lifespan. The caveat is that they havent actually tested >3 years, but IMO this is probably a 50 year battery. The paper is more conservative and gives it 20 years. This will be pretty enormous for grid storage, since a battery that lasts 5x as long costs 5x less. It may be important for trucks and buses, since they are much higher mileage and will want to run at 100% depth of discharge. Cars on the other hand run closer to 20%, where normal batteries will also last for many thousands of cycles.
- DuskStar 7y ago
  > since a battery that lasts 5x as long costs 5x less. This is only true if there is an inflation-adjusted discount rate of 0%, which is unrealistic even in this era of low interest rates. Adjusted for inflation, paying $10 now and again at years 10, 20, 30 and 40 is better than paying $50 up front would be. (By adjusted for inflation, I mean that the $10 you pay in 10 years might actually be $11, but still $10 in 2019 dollars)
  - BubRoss 7y ago
    That's assuming that batteries would stay the same price while currency inflates.
    - DuskStar 7y ago
      It's assuming that the item you're purchasing would maintain the same real price. If it cost $10 to start, and after 10% inflation the battery now costs $11, this holds. (Well, it holds if you have some way to beat inflation with safe returns. US government bonds often but not always meet this requirement) In the case of batteries specifically, I think it's likely that prices drop even without adjusting for inflation. This makes the price advantage even clearer.

alanh 7y ago

what is 'state of charge swing'?

hwillis 7y ago
I think it is referring to the fact that it is ubiquitous to leave some amount of reserve so that the battery is never fully charged (100% SoC) or discharged (0% SoC). This formulation is capable of going the full 0-100%, while most formulations will last significantly longer if they don't do that.[1] In that graph, charging to 75% and discharging to 25% gives you about 3x more life than from 25%-100%. NB that most li-ion cells are rated for 300-1000 cycles at 100% Depth of Discharge. Reducing the DoD to 90% or 80% will get you thousands or tens of thousands of cycles, although it is abnormal to actually measure that long. A charge-discharge cycle at .1 C (the former standard) takes 20 hours. [1]: https://batteryuniversity.com/_img/content/DST-cycles-web2.jpg https://batteryuniversity.com/_img/content/DST-cycles-web2.j...
- FooHentai 7y ago
  24kw leaf battery is an example of this with user stats seemingly bearing it out. Charge it to 80% each time, you can expect 3000 cycles before it's spent (drops below 85% of original capacity). If you charge to 100% each time, you'll only get 1000 cycles. 3-4 years versus 8-10 years use makes a big difference.
  - taneq 7y ago
    The 85% capacity benchmark seems pretty arbitrary to me. I'd imagine most owners very rarely use more than 85% of their range (or at least, could avoid doing so easily) at which point 85% isn't "needs expensive battery replacement", it's just "slightly less range buffer". I imagine in 20 years' time we'll see plenty of old beaters, student cars etc. with 50% or less range that are still quite happily driving around.
    - drcross 7y ago
      That's already the case, you can pick up 2013 Nissan Leafs with very small batteries for small money. They're used for commute cars or grocery pickup.

hwillis 7y ago

1) 532 is not a new chemistry. It's not even the lowest cobalt chemistry; there's 511 and 811 beyond that (811, or 80% nickel, 10% manganese, and 10% cobalt, is not yet technically feasible). 2) Range is decreased. 532 has lower energy density. 3) Maybe..? But nothing truly significant. The additives in this chemistry mean a lot of heat gets generated during charge/discharge. Heat is the limiting factor during charge, so swapping directly to this would mean lower top charging speed. However with better cooling... maybe? It can sustain high charge current for longer, but not as high overall. 4) The buffer for EVs is ~10%. It's not a big factor in cost or weight. 5) Yes, 5x longer lifespan. The caveat is that they havent actually tested >3 years, but IMO this is probably a 50 year battery. The paper is more conservative and gives it 20 years. This will be pretty enormous for grid storage, since a battery that lasts 5x as long costs 5x less. It may be important for trucks and buses, since they are much higher mileage and will want to run at 100% depth of discharge. Cars on the other hand run closer to 20%, where normal batteries will also last for many thousands of cycles.

DuskStar 7y ago
> since a battery that lasts 5x as long costs 5x less. This is only true if there is an inflation-adjusted discount rate of 0%, which is unrealistic even in this era of low interest rates. Adjusted for inflation, paying $10 now and again at years 10, 20, 30 and 40 is better than paying $50 up front would be. (By adjusted for inflation, I mean that the $10 you pay in 10 years might actually be $11, but still $10 in 2019 dollars)
- BubRoss 7y ago
  That's assuming that batteries would stay the same price while currency inflates.
  - DuskStar 7y ago
    It's assuming that the item you're purchasing would maintain the same real price. If it cost $10 to start, and after 10% inflation the battery now costs $11, this holds. (Well, it holds if you have some way to beat inflation with safe returns. US government bonds often but not always meet this requirement) In the case of batteries specifically, I think it's likely that prices drop even without adjusting for inflation. This makes the price advantage even clearer.