Have you ever noticed that a lithium battery's voltage drops right after it's fully charged? This is not a defect—it’s a normal physical behavior known as voltage drop. Let’s take our 8-cell LiFePO₄ (lithium iron phosphate) 24V truck battery demo sample as an example to explain.
1. What Is Voltage Drop?
Theoretically, this battery should reach 29.2V when fully charged (3.65V × 8). However, after removing the external power source, the voltage quickly drops to around 27.2V (about 3.4V per cell). Here’s why:
- The maximum voltage during charging is called the Charge Cutoff Voltage;
- Once charging stops, the internal polarization disappears, and the voltage naturally drops to the Open Circuit Voltage;
- LiFePO₄ cells typically charge up to 3.5–3.6V, but they cannot maintain this level for long. Instead, they stabilize at a platform voltage between 3.2V and 3.4V.
This is why the voltage seems to "drop" right after charging.
2. Does Voltage Drop Affect Capacity?
Some users worry that this voltage drop might reduce usable battery capacity. In fact:
- Smart lithium batteries have built-in management systems that accurately measure and adjust capacity;
- Bluetooth-enabled apps allow users to monitor actual stored energy (i.e., usable discharge energy), and recalibrate SOC (State of Charge) after each full charge;
- Therefore, voltage drop does not lead to reduced usable capacity.
3. When to Be Cautious About Voltage Drop
While voltage drop is normal, it can be exaggerated under certain conditions:
- Temperature Impact: Charging in high or especially low temperatures can cause faster voltage decline;
- Cell Aging: Increased internal resistance or higher self-discharge rates can also cause quicker voltage drop;
- So users should follow proper usage practices and monitor battery health regularly.
Conclusion
Voltage drop is a normal phenomenon in lithium batteries, particularly in LiFePO₄ types. With advanced battery management and smart monitoring tools, we can ensure both accuracy in capacity readings and the long-term health and safety of the battery.
Post time: Jun-10-2025
