mux wrote:End of life, ... and that's typically defined at 80% of initial capacity left.
End of life is usually defined in economic terms, and 80% isn't the typical EOL threshold. 70% EOL or less is more common, see the numbers below to understand why.
Suppose you need 1Wh of capacity. You could define EOL as any percentage, for example if you define EOL as 80% you would need to start with 1.25Wh. If you define EOL as 70% you would need to start with 1.4286Wh. With EOL at 60% start with 1.6667Wh.
If loss is linear with time/usage, then the 80% battery would need to be replaced every 2T, and the 70% battery would need to be replaced every 3T. The 60% battery every 4T.
The cost of replacements over time is:
80%= CostPerWh*1.25Wh/2T = 0.65 CostPerWh/T
70%= CostPerWh*1.4286Wh/3T= 0.4762 CostPerWh/T
60% = CostPerWh*1.6667Wh/4T = 0.416666667 CostPerWh/T