The 12/24 controllers do require the battery connection first so they can decide whether you have a 12 or 24v battery system.
That is different from the issue of maybe frying the controller by not having a battery connection while the panels are connected, which can happen with some. Then there are some (at least one) that says don't have the panels and a load connected with no battery.
Safest thing to do for them all is just never have the panels connected without the battery connected, as recommended by previous posters.
