This is a handy little non-rechargeable CR2016 Lithium Coin Cell Battery!
Sitting at 20mm diameter and is 1.6mm thick it's small but packs a punch with a nominal voltage output of 3V and a capacity of 90mAh. For other drain rates the capacity may be reduced, check the datasheet! Note that these are often "stacked" to make a 6V CR2032-sized pack of batteries.
Brand may vary from the one pictured.
TECHNICAL DETAILS
- Maxell CR2016 datasheet (not the same brand but has details on usage)
- Diameter: 20mm / 0.8"
- Thickness: 1.6mm / 0.06"
- Weight: 1.8g