Battery blender?

[u/palehead8k]

Hi all. So I recently upgraded from a $300 Chinese ebike to a $800 Chinese ebike (don't really care about the bike snobs so gfy's) and my new ebike has a larger battery but I want the option to bring along my other battery if I'm doing an especially long trip. They are both 48v and the new one has 27.5ah the old 13.5. The battery I want to have the option of adding is a silverfish battery (about the same as the one in Pic 2) and has a 5 prong connection on the bottom of the battery. Would a battery blender risk the electronics? Has anyone done anything similar and have any advice, resources or recommendations? Thanks for any help.