Battery lifetime is measured by how many cycles of full charge and discharge it takes to get down to 80% max battery capacity. For the Vesper Endurance Battery, internal testing shows that this is more than 500 cycles. The battery will still be functioning, just at slightly reduced flight time at that point. It's similar to how iPhone batteries operate at reduced capacity over time.

Lithium-ion cells all also lose capacity over time in storage. Stored at 50-75% charge, Vesper batteries will take about 3 years to reach 80% capacity.

We also strongly advise ensuring that each battery has at least 50% charge every 6 months even if the unit is not in use. This ensures that the battery will not discharge completely, which could affect its ability to recharge.