Battery lifetime varies on usage but eventually you will need to replace the SmartCuff's battery.
You can always check if you need to replace the battery by taking off the the sensor box’s lid either by unscrewing the top of the small red box or by popping off the lid off the black box.
Next, take out and put back the battery and check if the led is blinking. If for any chance the led is not blinking, you'll need new batteries.
You’ll need 3V CR1632 batteries for a SmartCuff™ with a red sensor and 3V CR2032 batteries for a SmartCuff™ with a black sensor.
If needed, simply open the sensor box as explained above, replace the old battery with the new one.
After you place in the new battery the LED on the blood pressure sensor's printed circuit board (right next to the battery socket) will start to blink, signalling a successful battery replacement.