MINNEAPOLIS — A Minnesota businessman convicted of engineering a $3.65 billion Ponzi scheme now lives in a two-person prison cell, awakened at 6 a.m. each day by clanging door locks.

Tom Petters, who led the Petters Group Worldwide corporate empire until it collapsed in 2008, now teaches other inmates at the federal prison in Leavenworth, Kan., how to develop business plans. His bank balance now averages $100 a month. He spends his evenings in the prison library, researching ways he might overturn his conviction and a 50-year sentence that could keep the 54-year-old in prison for the rest of his life, Twin Cities Business magazine reported Wednesday.

In his first media interview since before his arrest in 2008, Petters continued to maintain his innocence. Similar to his testimony at trial, he said he was betrayed by trusted associates who took a legitimate business and turned it into a Ponzi scheme behind his back.

Editor Dale Kurschner, who conducted the five-hour interview, wrote that Petters “looks tan, well-groomed, physically fit, and overall, healthy. He’s calm, positive, exhibits a good sense of humor, and is passionate about his former business activities and goals.”

Petters told the magazine he spends his days looking forward to talking with family and friends.

“I look for the best I can find in any situation. Here I’m lucky to have email and phone access. I exercise a lot, outside whenever I can, mainly calisthenics and jumping jacks; I’m not a runner. I’m in a unit where I’m safe. There have been no altercations or arguments with inmates. I go to work each weekday in the education area, doing a class teaching business plans.”

Petters said his adult daughter, Jenny, “is doing extremely well for all that has happened,” but dealings have been difficult with his ex-girlfriend, Tracy Mixon, with whom he has 6- and 4-year-old sons.

“I haven’t had great communications recently with Tracy. We talked about her and the boys coming here, but for a long time she told them I was overseas, working on my appeal. One day on the phone recently, I had to tell them the truth,” he said.

Defense lawyers last week filed a long-shot petition with the U.S. Supreme Court to take up his case after a federal appeals court affirmed his conviction and sentence. He said he expects the courts will eventually vindicate him.

“I have a very strong faith in God, and I believe the truth will eventually set me free, so I work on strategy to get the truth told,” Petters said.

First Assistant U.S. Attorney John Marti, who helped convict Petters, scoffed at his claims he was wrongfully convicted.