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The CR series of batteries are the most common “coin battery” types used in most modern car key fobs in the past few decades. The most common car key fob battery is the ubiquitous CR2032 battery.
The “CR” before the numbers stands for two things. First, the “C” is for Lithium. The “R” is for round, the shape of the battery. Then next two numbers indicate the battery size. A CR2032 has a diameter (length across the battery) of 20mm, and a height of 3.2mm.
CR batteries a not rechargeable. A common rechargeable key fob battery is the VL2020.
Let’s take a look at each common battery.
Most common key fob batteries
The CR2032 is the most common key fob battery type. It’s small size makes it perfect to power lock/unlock functions of older key fobs. Modern smart keys may have a larger CR2450.
Often used is larger, modern smart key fobs, the CR2450 is the largest commonly used key fob battery. It’s large capacity can handle years of passive connectivity such as on BMW‘s comfort access key fobs.
See my in-depth page on the CR 2450 battery.
The small CR2025 is often combined with itself to form a larger battery cell. This is the case in many Ford smart fobs where two CR2025 batteries are required.
The smallest common key battery, the CR2016 is found in Scion unlock/lock fobs. Due to it’s small size, this key battery is usually found only on fobs that lock or unlock a vehicle.