As Jon says, I replaced my Plus 8 one (after 11 years) and it's accessible from the top if you are reasonably agile, I'm 74..

I replaced like for like @ 11 years it owed me nothing and never saw a battery charger but I use it throughout the year.

The radio memory will go as will the temporary fine mixture adjustments for the ECU but a few miles down the road and it will relearn.r [Linked Image]

This was mine 68 quid delivered.