A single cell's voltage depends on its chemistry. While a common misconception is that all cells produce a single voltage, the truth is more nuanced. Let's explore different types of cells and their respective voltages:
Lead-Acid Cells
- Nominal Voltage: The nominal open-circuit voltage of a fully charged lead-acid cell is approximately 2 volts. This is consistent regardless of the cell's size. ([Reference: Progressive Dynamics, Battery University])
- Charged Voltage: When measuring the open-circuit voltage (OCV) of a charged and rested lead-acid battery, you should expect around 2.1 volts per cell. ([Reference: Battery University])
- Charging Voltage: Noticeable gassing typically begins when the voltage surpasses 2.30 volts per cell during charging. ([Reference: Xtra Power Batteries])
Lithium-ion Cells
- Nominal Voltage: Lithium-ion cells have a nominal voltage of around 3.7 volts. ([Reference: Large.net])
- Charging Voltage: Smartphones often operate between 4.2 and 4.4 volts. ([Reference: Large.net]) However, they generally don't charge to 100% to prolong battery life. ([Reference: GM Volt Forum])
Other Cell Types
Different battery chemistries (e.g., nickel-cadmium, nickel-metal hydride) will have different nominal voltages. The specific voltage should be referenced in the battery's specifications.
Human Cells
It's important to distinguish between the voltage across a cell membrane and the voltage of a battery cell. The average potential difference across a human cell membrane is about -70 mV or 0.07 volts. This is not the same as the voltage of a battery cell which provides usable electrical power. ([Reference: Reddit - Biology])
Conclusion
The voltage of a cell is not a single, universal value. It varies greatly depending on the cell's type and chemistry. Lead-acid cells typically have a nominal voltage of 2 volts, while lithium-ion cells are closer to 3.7 volts. The voltage across a human cell membrane is significantly lower at approximately 0.07 volts.
