# Are the maximum battery voltage and the open circuit voltage (equivalent circuit ) of the battery the same?

If you model the battery equivalent circuit with Rint circuit, Are the maximum battery voltage and the open circuit voltage of the battery the same?

And can we interpret the range in which the terminal voltage decreases due to the resistance of the circuit when the current flows as the available voltage range of the battery?

Ex. battery info. Max output voltage : 900 Vdc Output voltage range : 650 - 900 Vdc

If you model the battery equivalent circuit with Rint circuit, Are the maximum battery voltage and the open circuit voltage of the battery the same?

Yes. Because in open-circuit no current is flowing, therefore no voltage drop across the resistance. That means if you measure the terminals you measure the actual internal battery voltage.

And can we interpret the range in which the terminal voltage decreases due to the resistance of the circuit when the current flows as the available voltage range of the battery?

In part. Don't forget the battery voltage itself decreases as the battery discharges. So the open-circuit voltage itself decreases as the battery is discharged.

• I know that the voltage doesn't change much in the 30 to 80% range. So, does that mean the modeling I'm talking about is correct in this range?
– Lee
Mar 23, 2021 at 7:05
• @Chan If I understand what you are asking, yes. Mar 23, 2021 at 7:05
• Thank you, I understood the concept well
– Lee
Mar 23, 2021 at 7:09

Maximum battery voltage is achieved when there is no load on the battery (open circuit) and the battery is fully charged (100% SOC), if there is a load then the internal resistance will cause the terminal voltage to drop, if the battery is not fully charged then the terminal voltage will be lower.

So at 100% state of charge, after just disconnecting the battery from the charger the open circuit voltage will equal the maximum, other than that no, they won't be equal.

Also, many batteries may be charged to higher voltages but then after disconnecting from the charger would settle at lower voltages, for example lithium charged to 4.2V may settle at 4.1V, nickel metal hydride charges to 1.6V and settles at 1.3-1.4V, and lead acid charges to 2.3V but settles to 2.2V