wait so they refitted the ships and then basically use them as normal sea combat ship?
Well, they intended to. Their main use to Tirpitz was something else though: Marking them as obsolete so that he could push through more procurement of "real" battleships to replace them. The replacement ships came off the slips between 1909 and 1912.
They were pretty much reserve ships from their refit up until WW1. Well, technically they were part of the "Active Battle Fleet" until late 1904. Following that there were some larger-scale exercises in which the ships were activated and formed active combat ships in regular units. During this time - mostly in 1904 - they also did foreign visits as part of longer sea cruises, such as all around the UK with visits to e.g. the Shetlands, or visits to Morocco.
In the autumn maneuvers in 1909 all eight ships were activated and constituted into a single squadron, which served apparently as escorts for a transport convoy and then supported an amphibious landing with gun fire. In other maneuvers, e.g. in 1907, ships of the class served in mixed squadrons with other battleships. The homogenous squadron was an idea that came up in 1907 when the High Seas Fleet was constituted; the HSF consisted of two eight-ship battleship squadrons, with the eight obsolete Siegfried class ships forming a reserve third squadron for that.
Following the start of WW1 the VI. Squadron was constituted with the eight activated ships. However, since there wasn't really any high-sea action that these slow ships could take part in, the VI. Squadron was operationally distributed to serve coincidentally in exactly the original role - protecting the mouths of the major rivers. Only one of them saw some action in this role - SMS Hagen rescued the crew of cruiser SMS Yorck that had run into a minefield in their AoR in November 1914. SMS Beowulf was reassigned to support operations in the Baltic Sea from May 1915, firing her guns at land targets in these.
The VI. Squadron was dissolved on August 31st 1915 with the ships mostly relegated to coastal artillery divisions until manpower shortages had the Navy deactivate them and reassign the crews in early 1916.