A CR1220 battery may be a temporary substitute for a CR1620 battery in some cases but the CR1620 is not a suitable substitution for a CR1220 and the two batteries are not interchangeable. Individuals should use the size recommended by a product's manufacturer in all cases.
CR1220 and CR1620 batteries are both 3-volt lithium batteries. Both of them are 2 millimeters high, but the CR1220 has a 12.5-millimeter diameter and the CR1620 battery has a diameter of 16 millimeters. A product with a battery compartment that fits a CR1220 battery cannot accommodate a CR1620 battery in most cases, although a CR1620 battery compartment may allow the use of a CR1220. The difference in size gives these batteries different capacities.