eli5, why do batteries from the factory last so long?

Question

Watches, key fobs, car batteries all seem to last at least 5 to 10 yrs, sometimes longer. But once they are replaced, you need to do so yearly?

In: 10

Answer 1

Usually it’s because the manufacturer will use high-quality batteries with a guaranteed lifetime, so that they don’t need replacing within the warranty period.

Whoever is replacing them is using cheaper batteries. It’s as simple as that.