This is one of the most important features that you want to keep a close eye on when sleuthing for new emergency radios. A replaceable battery is a good thing to have, because it allows you to swap out the battery over time.
Here’s the deal: rechargeable batteries don’t last forever. Every time you fill and drain, the capacity of the battery is reduced by a miniscule amount. After a few seasons with significant use, the battery simply won’t last as long. It is also possible to swap out for a battery with greater capacity, as long as that battery conforms to the specifications of the radio itself.