Running the Organelle on batteries is possible, and it shouldn't damage the hardware or SD memory, but we don't officially recommend it for a couple reasons. Both of these have to do with the batteries running low. First, the Organelle will power off without shutting down. This shouldn't damage the hardware (or SD card which is read only), but files could get corrupted on the USB drive. Many of the patches write files to the USB drive, so you want to make sure those processes finish before power is removed. The second issue we noticed happening is loud noise coming from the audio output when the batteries die (enough power to have the audio hardware powered up, but CPU powered down), which is not really workable in any kind of live setting!
So it is possible, but only for experimental / use at your own risk scenarios.