I refused to be coerced into buying a new reader by the built-in obsolescence of a difficult to replace battery. So I persuaded a techie friend to change the battery of my prs 505. I bought the replacement battery for very little from Amazon, and he used tools he had handy. I printed out an MS Word doc which I obtained from MR and some pages of a PDF which detailed the relevant parts of the 505 (the pdf was also available from MR).
But I did think that Sony had made the battery so hard to replace to encourage me to spend money on a new model! Why not just have a compartment, easily accessed, where the old battery can be slipped out and a new one slipped in; at most, just a couple of screws to undo?