As of my last knowledge update in September 2021, flexible printed batteries can come in various voltage ratings, depending on their specific design, chemistry, and intended applications. The voltage rating of a flexible printed battery is typically determined by the materials used in its construction and the arrangement of its cells.
Common flexible battery chemistries, such as lithium-ion or lithium-polymer, usually provide voltages in the range of 3.6 to 3.7 volts per cell. These cells can then be connected in series to achieve higher voltage ratings. For example, a battery consisting of two cells in series could provide a total voltage of around 7.2 to 7.4 volts.
It's important to note that advancements in battery technology and manufacturing may have occurred since my last update. To get the most accurate and up-to-date information about the voltage rating of a specific flexible printed battery, I recommend checking with manufacturers or industry sources that specialize in flexible battery technology.