Arney,
Unfortunately, the built in battery is not replaceable but it does have a separate compartment to house user-installed batteries. Again unfortunately, the built in generator doesn't charge the user-installed batteries. I share your "thing" for hand-crank radios and this model from Sony has been the best so far. I have a Jensen, Eaton and a couple of made in China crank radio's and the Sony gets the best reception (despite it's dial tuner), and seems to be the best built of the bunch. As you may be able to see in the pictures, I have a piece of tape over both switches (LED & radio), to keep them from moving to the "on" position while in my BOB, that happened to me several times before I taped them down.