Yep! Old batteries tend to still hold a charge quite well- they become less efficient under the same load, which gives the impression that they lose capacity m

Yep! Old batteries tend to still hold a charge quite well- they become less efficient under the same load, which gives the impression that they lose capacity much faster than is actually the case. If you derate them they perform quite well- a battery may last 60% as long as it did originally, but when used more slowly it will hold more like 80% of its original capacity. In fact, battery degradation has in some cases been slower than battery innovation! Batteries have gotten better so quickly that the newer ones may have 50% more capacity even if the old ones didnt degrade much at all. Edit: its also complicated by the multitude of batteries and chemistries. Li ion is incredibly diverse compared to other battery families, and the various types can't be used together. Practically speaking you can only reuse batteries of a single chemistry and form factor, and the chemistry changes every few years or less. Its just not a stable enough industry for that yet.