I vaguely recall there were connections on the jetty at DOLPHIN and more firmly that there was a power house for machines to convert the normal AC supply into DC. As happens it was manned by the local Electrical Trade Union secretary and through him I got the valued skilled membership card that was very useful in finding civilian work when I left the RN, in the period before we sailed to NZ.
I didn't think much about these shore connections at the time as they were common in the main dockyards simply to supply DC power to ships alongside.
The drawings for the 'A' class clearly show labeled shore charging connections and ammeters, but we never used these connections in normal service outside the main dockyard in refit when obviously the engines could not be used. Even then I think when the refurbished battery was refitted, the service load was supported but no charging.
I believe the depot ships had charging kit, yet the SCOTSMAN was always charged by another submarine even if alongside the depot ship.
http://www.submariners.co.uk/Dits/Articles/scotsman.phpPerhaps in the early days of the smaller boats, they charged them more often from shore?
All more info than anyone wants to know, but battery charging was a big business in boats in all circumstances.
Lofty