I have already done that so that no optimazing battery closes it on bg if I listen to music. However on Samsung ultra powersave mode you select which apps you want to use. But Poweramp doesn't support it and it is not listed. Samsung music player is supported tho and it works on ultra powersave. But you know Poweramp is way better music player. Even Facebook & messenger work in ultra powersave XD but if you have open screen & Facebook & data powersaving doesn't do much. But I believe Poweramp could be listed there and work pretty well tho and with closed screen I would no longer worry about battery drain on my trips.