Nope, don't have to disconnect the batteries or even have them switched off. Just have to carefully open them to see the levels. And fill, as necessary. With the right water!
There are sealed batteries made that don't need to be checked. Some people love them, others have gone from them back to the ones needing to be checked. They are more expensive initially.
And I concur with the view of NOT letting these batteries completely loose a charge. While many kinds of batteries should be discharged occasionally, that's not true of these. There's a link somewhere on this forum to battery care - will go see if I can find it.
Here's the article I've posted before:
http://www.windsun.com/Batteries/Battery_FAQ.htm
Beth
“Dare to live the life you have dreamed for yourself. Go forward and make your dreams come true.” ~ Ralph Waldo Emerson ~
"He who treasures the small things in life has found the path to true happiness"