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battery glossary

OCV Curve

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Open Circuit Voltage (OCV) is a measurement of a battery cell’s voltage at a known state of charge when at resting equilibrium. The OCV curve is the mapping of the OCV from 0-100% SoC. A simple but imprecise method of estimating State of Charge is to use the manufacturer-defined relationship between voltage and charge level to look up the SoC based on a measured OCV. OCV can also be used to improve other charge-tracking methods like Coulomb Counting. Both techniques can be unreliable in many cell chemistries, especially Lithium Iron Phosphate (LFP), where the OCV relationship to charge is flat and there are significant hysteresis effects. It also fails to take into account other factors such as age, temperature, and time since the cell has last been used.

What is an Open Circuit Voltage?

Open Circuit Voltage (OCV) is a measurement of a battery cell’s voltage at a known state of charge when at resting equilibrium. The OCV curve is the mapping of the OCV from 0-100% SoC.
A simple but imprecise method of estimating State of Charge is to use the manufacturer-defined relationship between voltage and charge level to look up the SoC based on a measured OCV. OCV can also be used to improve other charge-tracking methods like Coulomb Counting. Both techniques can be unreliable in many cell chemistries, especially Lithium Iron Phosphate (LFP), where the OCV relationship to charge is flat and there are significant hysteresis effects. It also fails to take into account other factors such as age, temperature, and time since the cell has last been used.

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