Cerberus can last up to an hour in combat

Below them Cerberus smashed through the low wall around the garden and sent chunks of mortar and cinder blocks flying. An angry backhand crumpled the front of Mean Green.
They flew over Five and Four. “He’ll run out of power using it like that,” Danielle gasped. “Without Barry recharging it, the suit won’t last long at all.”
“How long?”
She was taking quick breaths through her nose. “Put us down.”
He dropped down between Stage 4 and the Edith Head Building. A few people watched them land, drawn out by the sounds. Danielle relaxed as the walls rose up around them and he set her on the ground. “Maybe forty-five minutes,” she said. “An hour tops. If you can just keep him—”

Excerpt From Ex-Purgatory, pg 608
Peter Clines
https://books.apple.com/us/book/ex-purgatory/id676938479