Zojirushi rice cookers have lithium batteries that are used only for retaining timer and cooking memory for if there is a power interruption. The batteries have an estimated lifespan of around 5-10 years depending on use. These batteries are not essential to the operation of the rice cookers but can be replaced only at authorised Zojirushi service centres if you feel you need to have it replaced. After warranty you would need to contact one of these centres if you wish the battery to be replaced.