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My LifePo4 battery has a 6000 cycle guarantee at 60% capacity. So its not even close yet

deng 4y ago
> So its not even close yet Yes, if you compare just capacity fade, that's true. But the longevity of LiFePo4 comes with a lower charge density than Li-Ion, about 170 mAh/g. This NaS battery currently has 1017 mAh/g, so almost a factor of 6. If the capacity is higher, you don't have to cycle as often, but of course, mileage depends on the use case.
- cogman10 4y ago
  That lower capacity comes at a cost cut and a huge materials advantage. LFPs are made of highly available materials. (Lithium, iron and phosphate). The higher capacity NMC batteries are constrained on nickel production.
Retric 4y ago
The question is more how many kWh can you store and extract over a lifetime at a given cost rather than how many cycles can it take. If the 5999th charge is only holding appropriately 60% of a LifePo4 battery you don’t get 6,000 cycles * full battery capacity.
- jacquesm 4y ago
  True, but you probably will get more before the battery becomes unusable in total. It would be very nice if batteries were super predictable as in 'perfect until the 6 thousandth cycle and then dead', instead you get this gradual drop-off to the point where a battery is no longer usable for its intended purpose. Whether or not that is at 60% of the original capacity or not is moot if it doesn't make it to the 60% in the first place (lots of batteries get murdered well before the end of their design life), on the other hand if that means that the drop-off itself slows down then you might be able to get much more life out of them when treated carefully. The big ones - in my experience, which is obviously not the final word on this - is to ensure that you don't charge batteries when they're very cold, that you don't use currents in excess of what they're made for (and preferably a bit below that) and that you don't subject them to mechanical stress. If you live by those rules you can make them stretch for a very long time, enough for technology itself, rather than that battery, to make your battery obsolete. Witness the old lead-acid batteries used in cars, telephone switch boards and submarines. In cars they would last a couple of years at best, in telephone switch boards and submarines they would routinely outlast the rest of the installation.

deng 4y ago

> So its not even close yet Yes, if you compare just capacity fade, that's true. But the longevity of LiFePo4 comes with a lower charge density than Li-Ion, about 170 mAh/g. This NaS battery currently has 1017 mAh/g, so almost a factor of 6. If the capacity is higher, you don't have to cycle as often, but of course, mileage depends on the use case.

cogman10 4y ago
That lower capacity comes at a cost cut and a huge materials advantage. LFPs are made of highly available materials. (Lithium, iron and phosphate). The higher capacity NMC batteries are constrained on nickel production.

Retric 4y ago

The question is more how many kWh can you store and extract over a lifetime at a given cost rather than how many cycles can it take. If the 5999th charge is only holding appropriately 60% of a LifePo4 battery you don’t get 6,000 cycles * full battery capacity.

jacquesm 4y ago
True, but you probably will get more before the battery becomes unusable in total. It would be very nice if batteries were super predictable as in 'perfect until the 6 thousandth cycle and then dead', instead you get this gradual drop-off to the point where a battery is no longer usable for its intended purpose. Whether or not that is at 60% of the original capacity or not is moot if it doesn't make it to the 60% in the first place (lots of batteries get murdered well before the end of their design life), on the other hand if that means that the drop-off itself slows down then you might be able to get much more life out of them when treated carefully. The big ones - in my experience, which is obviously not the final word on this - is to ensure that you don't charge batteries when they're very cold, that you don't use currents in excess of what they're made for (and preferably a bit below that) and that you don't subject them to mechanical stress. If you live by those rules you can make them stretch for a very long time, enough for technology itself, rather than that battery, to make your battery obsolete. Witness the old lead-acid batteries used in cars, telephone switch boards and submarines. In cars they would last a couple of years at best, in telephone switch boards and submarines they would routinely outlast the rest of the installation.