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If I remember correctly from building ebike battery packs, it’s mostly the heat that kills cycle life on 18650’s. On an ebike, its more of an issue since they can see 25-60A continuous (several minutes during hill climbing), allowing the individual cells to heat up quite a bit (4P config). Also voltage stress really hurts longevity too. EX charging to 4.2v=100% then discharge to 0% under load vs a more shallow 90% charge to 60-50% discharge.

On something like the X70, the heat from the led’s will likely step down the output current before the batteries really heat up too much. I think they are using VTC6’s and they may have data on cycle life vs heat on the spec sheet. If SONY doesn’t, find another similar 18650 (Samsung, Panny/Sanyo) and they will have the data and you can see what heat does to cycle life.

Anyways, after 2-3 years there should be much better chemistry and you can buy/build a replacement pack for your now 20th brightest light in the world (hopefully). :+1: