Lithium-ion batteries are the highest-rated pacemaker batteries available, as of 2015, according to the Central Intelligence Agency. Lithium-ion is the most common type of battery used in pacemakers because of its reliability and longevity. Lithium-ion batteries are expected to last 10 years or longer.
The battery decreases its voltage when it is near the end of its life, explains the CIA. Fortunately, the decreasing voltage is an end of life indicator for the pacemaker, which then lets the doctor know that it is time to install a new device. This feature of the batteries is very important as it allows time for the battery to be changed safely before it stops working altogether.