A Detailed Explanation of Milliampere-hours (mAh) and Watt-hours (Wh): A Scientific Interpretation and Practical Guide to Lithium Battery Capacity Units

I. Core Concepts: The Essential Differences between mAh and Wh
1. Milliampere-hours (mAh) — The "Container" for Charge
- Definition:Indicates the amount of current (in milliamperes, mA) that a battery can continuously discharge for one hour.
- Calculation Formula:
- Key Features:
- It only reflects the amount of charge stored in the battery and does not directly represent energy.
- It implicitly depends on voltage: When consumer electronics (such as mobile phone batteries) are labeled with mAh, a nominal voltage (such as 3.7V) is usually implied.
2. Watt-hours (Wh) — The "True Value" of Energy
- Definition:Represents the total energy actually stored in the battery, taking into account both voltage and charge.
- Calculation Formula:
- Key Features:
- It directly measures how much "work" the battery can perform and is a universally accepted unit of energy.
- It allows for direct comparison of energy across different voltages: Batteries with different voltages (such as a 12V lead-acid battery vs. a 3.7V lithium battery) can be compared directly in terms of Wh.

 II. Why Is Wh More Scientific Than mAh?
- Scenario Comparison:The Energy Difference Between Two "5000mAh" Batteries
- Conclusion: If only mAh is considered, the two batteries may seem identical; however, the high-voltage battery actually has double the energy. Wh more accurately reflects the endurance capability.

 III. Practical Applications and Common Questions
1. Why Do Aviation Security Regulations Limit Wh?
- Regulations by the International Civil Aviation Organization (ICAO):
- ≤100Wh: Allowed in carry-on luggage (such as most laptop batteries).
- 100–160Wh:Requires airline approval (such as high-end drone batteries).
- ＞160Wh:Prohibited from being carried.
- Conversion Example:A 20000mAh power bank (3.7V) would be...
2. How to Choose a Battery?
- For the Same Type of Battery (e.g., both 3.7V lithium batteries):Compare mAh directly.
- For Different Types of Batteries (e.g., lithium battery vs. lithium iron phosphate): Wh must be compared.