Is there any harm in switching a Perko while underway? I personally haven't because I didn't know if the alternater freak out if it didn't have a load on it. I've done this to vehicles (older ones, not new) and it wasn't any problem. The only reason I ask, is more than once, I have shut down to switch to a different battery because I forgot to earlier. I suffer from CRS syndrome (Can't remember Sh**).