I understand that with the proper charger (no internal battery), a timer can turn the charger off at the times one places the hearing aid in or removes it from the charger. What Im experiencing is that when the charger turns off, the hearing aids are on (as we want), but their proximity to each other causes a feedback sound to occur. Removing them from the charger creates more space between them and the feedback stops. If this on ok shabbas?

It's not a problem, for silencing feedback is not clearly prohibited, and regarding cases of Kavod HaBriyot (human dignity & self-respect) like hearing-aids, we are lenient on a psik reisha m'drabanan.