The hosts had sailed into a 2-0 half time lead at Damson Park courtesy of golas by Junior English in the 25th minute and Joel Grandison 8 minutes before the break.
Blues reduced the deficit just 5 minutes into the second period. Theo Streete handled Alpaslan Ozturk's cross into the box and Robin Shroot scored from the resulting spot-kick.
Shroot scored his and Blues' second of the night on 75 minutes when he finished well having been put through on goal by Jacob Hronec,
With the game looking to be heading towards a draw defender Kerr headed past Jack Butland in the Blues goal from a Ryan Beswick corner just two minutes from time.
Blues XI: Butland, Ozturk, Kerr, Nicholls, Matut (Hronec 60), O'Shea, Ghanore, Sammons, Newbury (Newall 67), Rowe (Reilly 83), Shroot.
Referee: Mike Bingham
Blues pre-season schedule continues this coming Saturday when they play their only home friendly of the summer against Spanish outfit Real Mallorca at St Andrews.