nothing other than you need a supply capable of delivering a MINIMUM of 5 Amps. When the motors peak or have an 'in rush' current, any less could overload a smaller power supply and cause it to fail.
in my honest and professional electrical experience, even the 24v units work better closer to or at 30v. the 24v was some sort of regulation they were forced to put in. I test all dolphin units I repair at 34v DC.