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] For a standard 3.7V lithium-ion cell, voltages under 3.0V indicate deep discharge. Prolonged operation below this threshold degrades capacity, increases internal resistance, and may cause catastrophic failure.
[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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