My 80 W iron gets plenty hot for soldering big stuff like 2 mm copper plate terminations and the like, but it seems to get too hot for maintaining a respectable layer of tin. I find I dab with solder, wipe it off, repeat 3 times and then I might have a shiny surface ready to solder with, only to have it burn and become solder repellent.
I think it needs a simmerstat turned up to 9/10ths to maintain a good temperature.
Otherwise, for soldering really big stuff, I wish I actually had a bigger one. 175 W would probably do nicely. So I can blast the copper plate, melt it onto the battery tabs, and have very little of the heat make it into the cells before being chilled with a ice-water sponge or something.