Monitoring the state of charge (SoC) in lithium-ion batteries is crucial for efficient use and maintenance. Several methods are employed to achieve this:
Common Methods for Monitoring SoC
- Open Circuit Voltage (OCV) Method:
- This method involves measuring the voltage of the battery when it is not in use (i.e., at rest).
- The OCV is correlated with the SoC, but the battery must be in equilibrium for an accurate measurement, which can take several hours.
- Coulomb Counting (Current Integration):
- This technique involves measuring the current flowing into or out of the battery over time.
- By integrating the current, you can calculate the total charge added or removed, thus estimating the SoC.
- This method provides continuous monitoring during battery use but may require recalibration to account for measurement errors.
- Impedance Measurement:
- This involves continuously monitoring the battery’s internal resistance and capacitance during operation.
- Changes in impedance can be correlated with SoC, allowing for dynamic monitoring without requiring the battery to be at rest.
- Volume Expansion Monitoring:
- Lithium-ion batteries change volume during charge and discharge.
- Techniques like using graphene sensors to measure these volume changes can provide insights into SoC and state of health (SoH).
New Technologies and Sensors
- Graphene Sensors: These can detect small changes in battery volume by monitoring electrical resistance changes, allowing for rapid SoC determination without interrupting battery operation. They also help detect early signs of cell failure.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-do-you-monitor-the-state-of-charge-in-lithium-ion-batteries/
