CR1225 vs CR1220
The CR1225 and CR1220 are the two largest members of the 12.5 mm lithium coin family, both 3 volts. The CR1225 stands 2.5 mm tall and holds 48 to 50 mAh, the most this diameter offers. The CR1220 is 2 mm tall with 35 to 40. Half a millimeter decides which one fits.
| CR1225 | CR1220 | |
|---|---|---|
| Chemistry | Lithium manganese dioxide (Li/MnO2) | Lithium manganese dioxide (Li/MnO2) |
| Voltage | 3 V | 3 V |
| Diameter | 12.5 mm | 12.5 mm |
| Height | 2.5 mm | 2 mm |
| Capacity | 48-50 mAh | 35-40 mAh |
| Also sold as | DL1225, ECR1225, BR1225 (wide-temp variant) | DL1220, ECR1220, BR1220 (wide-temp variant), 5012LC |
Everything here turns on that half millimeter, because the diameter and the voltage are identical. Compartments with springy contacts often take either cell, and where that is genuinely true the CR1225 is the better fill for its extra charge. Compartments molded to one depth do not negotiate at all. A CR1225 you have to press the cover down on is the wrong cell, and a CR1220 rattling in a 2.5 mm bay makes weak contact that shows up later as resets and dropouts. Neither is a drop-in for the other; each is a maybe that the housing settles.
What each size was chosen for answers the swap question most of the time. Thermometer and small medical device makers reach for the CR1225 because they want the reserve, and it also turns up in compact remotes and small flameless tealights. The CR1220 is the fob and scale cell: older Toyota and Subaru remotes, kitchen scales, watches, medical monitors and CMOS backup circuits. When a designer had room for the taller cell and specified the shorter one anyway, the housing is usually the reason, so treat the upgrade as opportunistic rather than routine.
Two side notes save trouble in this diameter. Both sizes have a BR twin, the BR1225 and BR1220, built on carbon monofluoride for a wider temperature range and slower self-discharge in exchange for capacity and pulse current. Cars and unheated outbuildings are where an engineer picks one deliberately, so if the old cell reads BR, buy BR. The other note is the CR1130, 11.5 by 3 mm, close enough in the hand to be mistaken for both of these and compatible with neither. Age matters too: brand-name coin cells hold their charge in the package for a decade, while loose bargain cells often arrive part drained, which is why a fob can feel weak straight after a battery change.