RE: can someone help me????
I've never used a seperate unit so not sure how it hooks up, I've only used ESC's with them built in. Basically when the LiPo reaches a minimum voltage (if you discharge a LiPo below 3.0V per cell it will ruin the battery) the cutoff will cut power. I've also seen some that just lightup an LED to let you know to stop.
Edit: [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXPGN1&P=7]Here[/link] is a Novak 4s LiPo cutoff. In order to use it though you would have to make a harness to connect your packs together (The ESC does this internally anyway so it wont hurt anything).
Edit 2: Removed