I read that it is permissible to use hearing aids on Shabbat as long as they are switched on before Shabbat. Furthermore some poskim permit adjusting the volume and some charging as well. Many hearing aids are chargeable either by placing them in a charging cradle connected to AC power supply (via a stepdown transformer). The hearing aid is switched off when the charger comes on. It does not come on automatically again, but needs to be switched on manually. Others can be charged in a battery powered cradle that was charged before Shabbat. Are either of these charging methods permissible on Shabbat? Additional information follows to evaluate this: When the hearing aids are put into the cradle, the hearing aids are switched off and an orange LED light comes on indicating the hearing aid is now off. The hearing aids are then charged. On removing the hearing aid it switches on and a green LED light comes on and a while later a sound is emitted to advise that the hearing aid is now on. A fully charged hearing aid will last about 22 hours if left on the whole Shabbat, which means the last two or three hours the hearing aid will no longer be active or 26 hours or more on two day holidays. Is there an issue of muktze once the hearing aid is discharged?

ב"ה Shalom, Sorry, I didn't answer you sooner. I wanted to answer your question before Shabbat, but I there were certain details which I wasn't able to verify on time. Recently, I have also familiarized myself with many of the Halachic issues of hearing aids. Although you mentioned many issues, I will only address your last question, which is: Does the hearing aid become muktzeh once the it is no longer charged? The opinion of many poskim is that the hearing aid is not muktze even it if is not charged, since it did not become useless item which has to be discarded, but temporarily is not functioning. See ישיב יצחק חלק לא סי' ט"ו , במנחת שלמה ח' ב' סי' י"ח וכ"כ בשו"ת שבט מיהודה ח"ב סי' ל"ה בשם החזון איש שהתיר למעשה ולא חשש משום מוקצה עיין ג"כ בשו"ת באר משה ח"ו קו"א י"ד אות א ד"ה ועוד ושו"ת יביע אומר ז או"ח לח ג There are some poskim who see it as muktze because of "issur" , but it seems one can be lenient on this issue. See שמירת שבת כהלכתה פרק כח הערה מז וראה גם הערה נב All the best