As some used to “gotchas” and things aren’t free, I’m wondering what kind of shortcomings[1] these batteries have that others do not.

[1] for example acid batteries can push a lot of power, but they are heavy and contain lead and well… acid. The nickel cadmium doesn’t contain lead and acid, but has memory so you should follow discharge them before charging again. They are lighter, but still not light. Lithium ion are light, don’t have memory, but can explode, also lose life if they are kept fully discharged or charged for long periods of time. They also slowly discharge when not in use, mainly due to protective circuit needing electricity to run.