I concur, Andy, and would just like to add a couple of additional points.
Charge efficiency can be up to 95% for standard lead-acid batteries, but as low as 70% for gel types, so be prepared for even longer charging times if you have that type.
Also, with standard types you can see when full charge has been reached by the gassing of the electrolyte, if it's an old-fashioned one with removable caps to the cells.
It is bad news to continue charging when the gas stage has been reached, so either then drop the charging voltage back down to around 13.8 volts (14.8 - 15 volts to gas stage) or get a clever charger that does it automatically.
Halfrauds do one, but you MUST disconnect the battery completely with that, because it uses pulse charging, which would upset the car's electronics.
I hope that helps; battery charging can be a lifetime study!
Ron.