The supposed limit of active battles in the same minute is 3. This means finishing one at the beginning of the minute, doing another & starting a 3rd at the end of the minute is still out. At least that's the system in DMM as far as I know.
Other than that, there are the outright cheats, like being active in multiple battles, scripting & the likes.
I just google translate it. It isn't good with detailed information, but if you get used to its silliness, even the mistranslated parts tend to follow pattern.
As for the link.. http://xn--hckqz0e9cygq471ahu9b.xn--...BC%B7%E5%8C%96
If you plan to use this wiki & have trouble navigating through it, there's a link in my signature for a guide on how to use it.
EDIT: nice avatar, Kitty.