Comment by TMWNN

My experience with a very high-end solar Casio was akin to yours, with the battery needing replacing after about five years. Perhaps gambiting is correct about the common nature of the battery, but multiple watch repair shops (both in a department store, and the "old man in a tiny room in an office building" type) refused to deal with it. I always had to mail it to an authorized Casio repair outlet.

I do not know whether this also applies to Eco-Drive.