The wren pumps are sized so that in the event of controller failure the turbine will not overspeed, you would be safe on a single LiPo at 3.7v but you may not get full power. 7.4v (2S) LiPo may not offer you the safety and may damage the controller and other aspects. You would be better to talk to Sara at Wren on this subject, your ECU may be different to mine.
J
