The Li-ion cells can be replaced quickly using hand tools. It appears to take forty 18650 cells, which cost about $5/cell for high-capacity cells purchased from

The Li-ion cells can be replaced quickly using hand tools. It appears to take forty 18650 cells, which cost about $5/cell for high-capacity cells purchased from reputable dealers in small quantities. Given their suggestion of replacing cells every 3 years, I find their claimed operating cost of $16/year questionable. Using the cheapest Li-ion cells you can possibly find is a good way to test how fireproof that casing really is. I like this idea, and I'd like to see user-serviceable batteries for nearly everything that uses one, but I don't love the marketing here.