The firm, which emerged from Loughborough University, manufactures zero-emission fuel cells and now has 250 staff across the UK, California, India and Japan.
Intelligent Energy previously used AxiCom to handle its PR, but split the brief into two separate accounts as it wanted to bring specialist financial PR firepower on board.
Last month, it brought in Racepoint Group to deliver trade and consumer PR campaigns, and has hired Powerscourt to advise on more business-oriented comms. The Powerscourt team is led by partner Giles Sanderson.
In February, Intelligent Energy closed a $30m (£18.8m) fundraising, which valued the firm at around $500m (£314m). It is thought that Powerscourt will look to communicate directly to the UK investor community and grow Intelligent Energy's corporate profile and capitalise on recent growth.
Earlier this year, the firm signed a joint agreement with Suzuki Motor Corporation to develop zero-emission fuel cell systems for vehicles, which were then used for transporting VIPs during London 2012.