[verisimi]

The 7 years thing is from the idea I have heard that after around 7 years the functional life of the battery is effectively over.

> The Li-ion battery typically has a lifespan of 300-500 charge cycles. Suppose a fully discharged lithium-ion battery provides 1Q of charge, and not considering the decrease in charge with each charge, the lithium-ion battery can provide or replenish a total of 300Q-500Q of charge over its lifetime. It can be seen that if charged to 1/2 each time, it can be recharged 600-1000 times; if recharged to 1/3 each time, it can be recharged 900-1500 times. And so on and so forth, with an indeterminate number of charges if they are randomized. In any case, no matter how you charge, the total amount of energy replenished remains constant at 300Q-500Q.

https://cmbatteries.com/comprehensive-understanding-of-lithi...

[Tagbert]

Except there are thousands of EVs out there older than 7 years old that have no problem with their batteries. The whole point of this article is that batteries are lasting much longer than the earlier assumption suggested. Your assumption of 300-500 charge cycles is an example of that. Actual charge cycles are 3-5 times greater. Aside from some problems with early chemistries like the Nissan Leaf battery, battery life is not a problem for long lasting EVs.