Wh vs mAh on Laptop Batteries: A Complete Guide for Buyers
When shopping for a replacement laptop battery, you’ll encounter two key specifications: Watt-hours (Wh) and milliampere-hours (mAh). Understanding the difference is crucial for choosing the right compatible battery for your device. This guide explains both units in simple terms.
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What is mAh (Milliampere-hour)?
mAh measures the battery’s charge capacity. It tells you how much electric charge the battery can store. A higher mAh rating generally means the battery can power your device for a longer time if the voltage remains the same. For example, a 4000mAh battery can theoretically deliver 4000 milliamps of current for one hour.
What is Wh (Watt-hour)?
Wh measures the battery’s energy capacity. It represents the total amount of energy a battery can deliver. Wh is a more comprehensive unit because it accounts for both voltage (V) and charge. The formula is: Wh = (mAh × V) / 1000.
Why Wh is Often a Better Indicator
When comparing replacement batteries, Wh gives a more accurate picture of potential runtime than mAh alone. This is because laptop batteries operate at different voltages.
| Battery A | Battery B | Comparison |
|---|---|---|
| 4000mAh, 10.8V | 4000mAh, 14.4V | Same mAh, different voltage |
| 43.2 Wh | 57.6 Wh | Battery B has more total energy |
As shown, even with the same mAh, Battery B will likely last longer because it has a higher Wh rating.
How to Choose the Right Replacement Battery
Follow these steps to ensure compatibility and performance:
- Check Your Original Battery: Always look for the Wh or mAh and Voltage (V) rating on your current battery.
- Prioritize Wh: If possible, match or slightly exceed the original Wh rating for similar or better runtime.
- Understand mAh with Voltage: If only mAh is listed, you must ensure the voltage matches exactly. A higher mAh with the same voltage is acceptable.
- Verify Compatibility: Use your laptop’s exact model number to find the correct compatible replacement.
Quick FAQ
Can I use a battery with a higher Wh rating?
Yes, if it is physically compatible and operates at the same voltage. A higher Wh means more energy and potentially longer battery life.
My old battery lists only mAh. What should I do?
Find the voltage (V) on the old battery label. Then, you can calculate the Wh or simply ensure any replacement has the same mAh and the same voltage.
Is a higher mAh always better?
Not necessarily. If the voltage is different, a higher mAh might not translate to more energy. Always consider both values together.
Find Your Perfect Replacement Today
Choosing the right battery doesn’t have to be confusing. By understanding Wh and mAh, you can make an informed decision and find a high-quality compatible battery that meets your laptop’s needs.