Can you find out how often that you could recharge your rechargeable batteries?
There are two general different types of rechargeable battery devices: NiMH and NiCd.
(Nickel-Cadmium and Nickel-Metal Hydride)
Does your rechargeable device, for your hearing aids, have a switcher for you to pick one of these batteries?
My twelve NiCd batteries for my digital camera have been recharged about 200 hundred times for a few years. After that, they started to wear out that last about 100 pictures. It used to be about 300 pictures as new fresh batteries. I think I was told that the slower charger is better which let the batteries hold much longer than a faster 1-hour charger. But, I made a choice to buy a faster one that saves my time. I still use my batteries now ever since I bought them.
Battery (electricity) - Wikipedia, the free encyclopedia