I am designing a wearable for medical application and I am searching for a rechargeable small size battery. I have searched a lot,but couldn't find one. Can anyone help me with some ideas/options?
Rechargeable hearing aids must have tiny batteries. Not sure about rechargeable electric toothbrushes.
The smallest rechargeable I have seen sold is 'N' size. 1.5V. About half the length of AAA. They were around a couple decades ago. You may need to search to find them today.
Each of my hearing aids use one tiny 312 zinc-air battery cell that is inexpensive and lasts for one week. Watches use the same cell. Rechargeable battery cells are not needed.
Toy and hobby remote controlled helicopters use a small rechargeable Li-Po battery cell.
What size is your wearable device? Do you know what is the current consumption? Most of today’s wearable devices (non-medical, iWatch for example) use lithium ion batteries. If the device is small and high current consumption, you don’t have much choice but go with lithium batteries.