Impact of Charging Voltage on Lithium-ion Battery Performance
1. Cycle Life vs. Charging Voltage
– Most lithium-ion cells are charged to a standard peak voltage of about 4.20V per cell. Charging to this voltage typically yields a cycle life of around 300–500 charge/discharge cycles.
– Reducing the peak charge voltage by 0.10V per cell can approximately double the battery’s cycle life. For example, charging to 4.10V/cell can extend the cycle life to about 600–1,000 cycles; charging to 4.00V/cell can yield 1,200–2,000 cycles; and charging to 3.90V/cell can extend life even further to 2,400–4,000 cycles.
– The optimal voltage for longevity is around 3.92V/cell, which minimizes voltage-related stresses that contribute to battery degradation.
2. Capacity Trade-Off
– Lowering the charging voltage reduces the battery’s maximum stored capacity. Every roughly 70mV decrease in charge voltage results in about a 10% reduction in capacity. This means the battery will hold less energy and power less runtime between charges.
– However, if the battery is subsequently charged at the standard higher voltage, full capacity is restored. Thus, a balance can be struck depending on whether capacity or lifespan is prioritized.
3. Voltage Range for Charging
– The ideal charging voltage range for lithium-ion cells generally lies between 3.6V and 4.2V per cell. Charging below 3.6V is effectively deeply discharged and can harm battery health, while charging above 4.2V risks overcharging and damage.
– During charging, the voltage increases from about 3.6V at low state of charge to 4.2V at full charge. Toward the end of charging, the current tapers off as the voltage holds steady near 4.2V to ensure full capacity without overcharge.
4. Effects of Temperature
– Although not directly a charging voltage effect, battery voltage and capacity can be influenced by temperature, with lower temperatures causing lower voltage and capacity delivery. This interacts with charging voltage considerations since performance will differ under varying conditions.
Summary Table of Charging Voltage Effects
| Charging Voltage (V/cell) | Approximate Cycle Life | Capacity Impact | Notes |
|---|---|---|---|
| 4.20V | 300–500 cycles | 100% capacity | Standard full charge voltage |
| 4.10V | 600–1,000 cycles | ~90% capacity | Doubling life with slight capacity loss |
| 4.00V | 1,200–2,000 cycles | ~80% capacity | Longer life, moderate capacity loss |
| 3.90V | 2,400–4,000 cycles | ~70% capacity | Optimal longevity, significant capacity reduction |
| ~3.92V | Maximum longevity | Slight capacity reduction | Voltage stress minimized |
Conclusion
Charging voltage is a key parameter balancing lithium-ion battery capacity and lifespan. Higher voltages (near 4.2V/cell) maximize capacity and runtime but shorten cycle life due to increased voltage stress. Lowering the charge voltage reduces stress and greatly extends cycle life but at the cost of usable capacity. An intermediate charging voltage around 3.9–3.92V/cell is considered optimal for prolonging battery life without excessive capacity loss. This trade-off allows customization of battery use for either longer life or greater energy storage depending on application needs.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-charging-voltage-impact-the-performance-of-lithium-ion-batteries/
