Wh to mAh Calculator

Understanding the conversion between Watt-hours (Wh) and milliampere-hours (mAh) is essential for battery technology and energy management. This calculation helps determine battery capacity and runtime across various devices.

This article explores the technical details of Wh to mAh conversion, including formulas, tables, and real-world examples. It provides a comprehensive guide for engineers, technicians, and enthusiasts alike.

Artificial Intelligence (AI) Calculator for “Wh to mAh Calculator”

• Convert 36 Wh to mAh at 12 V
• Calculate mAh from 50 Wh at 3.7 V
• Find mAh for 100 Wh battery rated at 24 V
• Determine mAh from 10 Wh at 5 V

Comprehensive Tables for Wh to mAh Conversion

Below are detailed tables showing common Wh to mAh conversions at various voltages, reflecting typical battery voltages used in consumer electronics, electric vehicles, and industrial applications.

Fundamental Formulas for Wh to mAh Conversion

Converting Watt-hours (Wh) to milliampere-hours (mAh) requires understanding the relationship between energy, voltage, and charge capacity. The core formula is derived from the definition of electrical energy:

• mAh: milliampere-hours, the battery capacity in terms of electric charge.
• Wh: Watt-hours, the energy stored or consumed.
• V: Voltage of the battery or device in volts.

This formula assumes a constant voltage during discharge, which is a practical approximation for many battery chemistries.

Derivation and Explanation

Watt-hour (Wh) is a unit of energy, defined as power (watts) multiplied by time (hours). Power is voltage times current:

Where Ah is ampere-hours. Rearranging to find Ah:

Since 1 Ah = 1000 mAh, multiply by 1000 to convert:

Additional Considerations

• Voltage Variations: Battery voltage can fluctuate during discharge; nominal voltage is typically used.
• Efficiency: Real-world efficiency losses (heat, internal resistance) are not accounted for in this formula.
• Battery Chemistry: Different chemistries (Li-ion, NiMH, Lead Acid) have different voltage profiles.

Real-World Application Examples

Example 1: Calculating mAh for a 36 Wh Battery at 12 V

A technician needs to find the capacity in mAh of a 36 Wh battery rated at 12 V to compare it with other batteries.

• Given: Wh = 36 Wh, V = 12 V
• Formula: mAh = (Wh × 1000) / V

Step 1: Multiply Wh by 1000:

Step 2: Divide by voltage:

Result: The battery capacity is 3000 mAh at 12 V.

Example 2: Determining mAh for a 50 Wh Battery at 3.7 V

For a lithium-ion battery pack rated at 3.7 V and 50 Wh, calculate the mAh rating to assess compatibility with a device.

• Given: Wh = 50 Wh, V = 3.7 V
• Formula: mAh = (Wh × 1000) / V

Step 1: Multiply Wh by 1000:

Step 2: Divide by voltage:

Result: The battery capacity is approximately 13,514 mAh at 3.7 V.

Expanded Technical Insights

Voltage and Its Impact on Capacity Calculations

Voltage is a critical parameter in Wh to mAh conversion. The nominal voltage of a battery is often used, but actual voltage varies during discharge cycles. For example, a Li-ion cell nominally rated at 3.7 V can range from 4.2 V (fully charged) to about 3.0 V (discharged). This variation affects the accuracy of mAh calculations.

To improve precision, engineers sometimes use average voltage during discharge or integrate voltage over time for energy calculations. However, for most practical purposes, nominal voltage suffices.

Battery Chemistry and Voltage Profiles

• Lithium-ion (Li-ion): Nominal voltage ~3.6-3.7 V per cell.
• Nickel-Metal Hydride (NiMH): Nominal voltage ~1.2 V per cell.
• Lead Acid: Nominal voltage ~2.0 V per cell.

When converting Wh to mAh for battery packs, multiply the number of cells in series by the nominal voltage per cell to get total pack voltage.

Practical Use Cases

• Consumer Electronics: Smartphones, tablets, and laptops use Wh to mAh conversion to specify battery capacity.
• Electric Vehicles (EVs): EV battery packs are rated in Wh or kWh; converting to mAh helps in understanding cell-level capacity.
• Renewable Energy Storage: Solar battery banks use these calculations to estimate storage capacity and runtime.

Additional Tables: Extended Voltage Ranges and Capacities

Best Practices for Accurate Wh to mAh Conversion

• Use Nominal Voltage: Always use the nominal voltage rating of the battery for standard calculations.
• Account for Voltage Drops: For precise applications, consider voltage drop during discharge.
• Check Manufacturer Specs: Battery datasheets often provide both Wh and mAh ratings; verify calculations against these.
• Consider Temperature Effects: Battery capacity and voltage can vary with temperature, affecting conversions.

References and Further Reading

• BatteryStuff Wh to mAh Calculator
• Battery Council International: Understanding Battery Capacity
• EE Times: Understanding Battery Capacity and Energy
• Texas Instruments: Battery Capacity and Energy Calculations