What does Vload mean in the Battery Loaded Voltage formula?

Vload is Terminal voltage under load (V).

Battery Loaded Voltage

Q: How do you calculate Battery Loaded Voltage?

Use the formula Vload = Voc − I × Rint. A battery under load delivers less voltage than its open-circuit voltage due to the internal resistance voltage drop. Enter the values you know in the calculator above and it solves for the remaining variable.

Q: What is the formula for Battery Loaded Voltage?

The Battery Loaded Voltage formula is Vload = Voc − I × Rint, where Vload—Terminal voltage under load (V); Voc—Open-circuit voltage (V); I—Load current (A); Rint—Battery internal resistance (Ω).

Vload = Voc − I × Rint

Quick answer

This calculator solves Vload = Voc − I × Rint for Loaded Voltage. With Open-Circuit Voltage 26.4 V, Load Current 2 A, Internal Resistance 50 mΩ, the result is 26.3 V. It solves in 4 directions, so you can enter the values you have and get the one you need.

Calculator

Open-Circuit Voltage

Load Current

Internal Resistance

Loaded Voltage (V)

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Formula

Vload = Voc − I × Rint

Description

A battery under load delivers less voltage than its open-circuit voltage due to the internal resistance voltage drop. Internal resistance increases as the battery ages, discharges, or operates in cold temperatures. For lithium-ion cells, fresh internal resistance is typically 20-80 mΩ, rising to 200+ mΩ near end of life. At high discharge currents, the voltage sag can be significant and may cause the terminal voltage to drop below the minimum operating voltage of the connected circuit even when significant capacity remains.

Variables

Vload — Terminal voltage under load (V)
Voc — Open-circuit voltage (V)
I — Load current (A)
Rint — Battery internal resistance (Ω)

Practical Notes

Internal resistance can be measured by comparing voltage at two different load currents: Rint = (V1-V2)/(I2-I1). For high-current applications (power tools, EVs), low internal resistance is critical. Cell manufacturers specify AC impedance at 1 kHz and DC resistance separately. Battery management systems monitor internal resistance as a health indicator.

Symbols and units

Symbol	Meaning	Default unit	Accepted units
Vload	Loaded Voltage	V	pV, nV, µV, mV, V, kV
Voc	Open-Circuit Voltage	V	pV, nV, µV, mV, V, kV
I	Load Current	A	pA, nA, µA, mA, A, kA
Rint	Internal Resistance	mΩ	mΩ, Ω, kΩ, MΩ

Step by step

1. What you know: Open-Circuit Voltage 26.4 V, Load Current 2 A, Internal Resistance 50 mΩ
2. The relation: Vload = Voc − I × Rint
3. Substitute: Voc = 26.4 V, I = 2 A, Rint = 50 mΩ
4. Result: Loaded Voltage = 26.3 V

Related quantities from the same inputs

P = V × I = 52.8 W

Worked examples

Minimum range

Given: Open-Circuit Voltage 0.726 V, Load Current 2 mA, Internal Resistance 0.1 mΩ

Result: Loaded Voltage = 0.726 V

Low range

Given: Open-Circuit Voltage 7.26 V, Load Current 20 mA, Internal Resistance 1 mΩ

Result: Loaded Voltage = 7.26 V

Typical

Given: Open-Circuit Voltage 26.4 V, Load Current 2 A, Internal Resistance 50 mΩ

Result: Loaded Voltage = 26.3 V

High range

Given: Open-Circuit Voltage 0.506 kV, Load Current 100 A, Internal Resistance 0.5 Ω

Result: Loaded Voltage = 0.456 kV

Maximum range

Given: Open-Circuit Voltage 5.06 kV, Load Current 1 kA, Internal Resistance 5 Ω

Result: Loaded Voltage = 60 V

Solving for each variable

Solve for Loaded Voltage

Open-Circuit Voltage 0.726 V, Load Current 2 mA, Internal Resistance 0.1 mΩ → 0.726 V

Solve for Open-Circuit Voltage

Loaded Voltage 0.33 V, Load Current 2 mA, Internal Resistance 0.1 mΩ → 0.33 V

Solve for Load Current

Loaded Voltage 0.33 V, Open-Circuit Voltage 0.726 V, Internal Resistance 0.1 mΩ → 3.96 kA

Solve for Internal Resistance

Loaded Voltage 0.33 V, Open-Circuit Voltage 0.726 V, Load Current 2 mA → 0.198 kΩ

How Loaded Voltage changes with Open-Circuit Voltage

Open-Circuit Voltage (input)	Loaded Voltage (result)
5.81 V	5.326 V
14.53 V	14.04 V
29.05 V	28.57 V
43.58 V	43.09 V
58.1 V	57.62 V
87.15 V	86.67 V
116.2 V	115.7 V
0.2324 kV	0.2319 kV
0.4067 kV	0.4062 kV
0.581 kV	0.5805 kV

The same result in other units

Unit	Value
mV	26300
V	26.3
kV	0.0263

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Frequently asked questions

How do you calculate Battery Loaded Voltage?

Use Vload = Voc − I × Rint. With Open-Circuit Voltage 26.4 V, Load Current 2 A, Internal Resistance 50 mΩ, Loaded Voltage works out to 26.3 V.

What is the formula for Battery Loaded Voltage?

The formula is Vload = Voc − I × Rint. A battery under load delivers less voltage than its open-circuit voltage due to the internal resistance voltage drop.

How do you find Open-Circuit Voltage when you know the other values?

Rearrange for Open-Circuit Voltage: with Loaded Voltage 0.33 V, Load Current 2 mA, Internal Resistance 0.1 mΩ, Open-Circuit Voltage is 0.33 V.

How do you find Load Current when you know the other values?

Rearrange for Load Current: with Loaded Voltage 0.33 V, Open-Circuit Voltage 0.726 V, Internal Resistance 0.1 mΩ, Load Current is 3.96 kA.

What units does Battery Loaded Voltage use?

Loaded Voltage is shown in mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

Related Concepts

All Battery formulas →

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