CR1220
Direct Answer
A CR1220 coin cell is a 3.0V Lithium Manganese Dioxide battery measuring 12.5mm in diameter and 2.0mm in thickness, with a nominal capacity of about 35 mAh. Its small size makes it common in car key fobs, small LED lights, and low-power Bluetooth beacons.
Source: IEC 60086-3
Specs
| Diameter | 12.50 mm |
| Height | 2.00 mm |
| Nominal Voltage | 3.00 V |
| Nominal Capacity | 35 mAh |
| Chemistry | Lithium Manganese Dioxide |
A Compact Cell for Compact Electronics
At just 12.5mm across, the CR1220 is among the smallest coin cells in common use -- roughly 60% the diameter of a CR2032 -- yet it follows the same IEC 60086-3 naming convention, where '12' encodes the 12.5mm diameter and '20' encodes the 2.0mm thickness. That small footprint caps its capacity at around 35mAh, a fraction of the CR2032's 225mAh, but it's more than sufficient for the low-duty-cycle devices it typically powers.
Car key fobs are the CR1220's signature application: a fob only draws current in short bursts when a button is pressed, so even a small cell can deliver years of service, and the format's slim profile fits easily inside a key's plastic housing.
Beyond Key Fobs
The same combination of small size and long shelf life has made the CR1220 popular in other intermittent-use electronics, including some laser pointers, small LED flashlights, glucose meters, and Bluetooth low-energy beacons used for asset tracking. Because it shares its lithium manganese dioxide chemistry with larger CR-series cells, it delivers the same flat 3.0V output and multi-year shelf stability rather than the sloping discharge curve typical of alkaline cells -- a useful property when a device needs to behave predictably as its battery ages.