My ex has not seen the our kids in over a year and I was told that I could file for abandonment and he could loose all rights of the kids he is so far behind in childes support

Please provide your location as laws vary by locality.

I live in Madison Indiana

He needs to be abusive or neglectful - leaving the child unattended. Child Abandonment Laws in Indiana | eHow.com

I see no benefit to you IF you are able to cause him to lose all "rights" to the child. What is your purpose in doing this?

Failure to pay child support is not abandonment. Have you gone to a collection agency?

The Courts will NOT declare that he has abandoned his child(ren) when the issue is child support - visitation is not a club with which to beat the parent over the head.

You may use abandonment as a reason to file a motion to change his visitation and other rights, it does not get rid of his rights, only restricts his use, unless he fights it, or refiles latter asking for specific rights back.

Child support is not connected to his "rights" it is his obligation, and normally non payment or late payment is not a reason to lose other rights.