Not all CI's have rechargable batteries either. And I have yet to find a standard 675 hearing aid battery that is rechargable. Some of those CI's use standard 675 hearing aid batteries.
hmm, I had a rechargeable 675 system when I was in high school almost 20 years ago, I assure you there is one.... it was about an inche and a half long, with a sliding lid, and then the power plug to plug directly in the wall. It worked, but I didn't appreciate needing to change my rechargeables every day, and often forgetting to throw in the charger...... for 20 years now, I prefer disposeable in my HA.... they often last a week or more...