Each PV cell produces anywhere between 0.5V and 0.6V, according to Wikipedia; this is known as Open-Circuit Voltage or V OC for short. To be more accurate, a typical open circuit voltage of a solar cell is 0.58 volts (at 77°F or 25°C). All the PV cells in all solar panels have the same 0.58V voltage.
[pdf] A lithium-ion battery has a nominal voltage of 3.7 volts per cell. When connected in series, the total voltage increases by 3.7 volts for each cell. This configuration allows for different battery pack designs.
[pdf] A fully charged lithium-ion battery typically measures between 4.1V and 4.2V per cell. This voltage range represents 100% state of charge (SOC), and it’s the maximum safe limit for most standard lithium-ion chemistries. Charging beyond this level risks battery damage or safety hazards.
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