What is the difference between An Shi and Wa Shi
2025-09-25
Ampere hour (Ah) and watt hour (Wh) are two important units in the field of batteries, used to measure the capacity and energy of batteries, respectively. There are significant differences between the two in terms of definition, physical meaning, application scenarios, and interrelationships. Here is a detailed comparison:
1. Definition and Physical Significance
- Ah, Ampere hour
- Definition: Refers to the product of the duration of continuous discharge of a battery under specific discharge conditions (such as constant current) and the current.
- Formula: Ah=Current (A) × Time (h)
- Physical meaning: Reflecting the ability of a battery to store charge, that is, "how much current can be released". For example, a 10Ah battery can discharge for 10 hours at 1A current or for 1 hour at 10A current.
- Characteristic: Only considers the amount of charge, without involving voltage or energy.
- Wh, Watt hour
- Definition: Refers to the energy that a battery can output under specific discharge conditions, that is, the product of power and time.
- Formula: Wh=Power (W) x Time (h)=Voltage (V) x Current (A) x Time (h)
- Physical meaning: Reflecting the actual energy that a battery can provide, that is, 'what work can it do'. For example, a 100Wh battery can power a 10W device for 10 hours or a 100W device for 1 hour.
- Features: Combining voltage, current, and time to directly correlate energy output.
2. Core Differences
| dimension | Anshi (Ah) | Watt hour (Wh) |
|---|---|---|
| physical quantity | Charge quantity (current x time) | Energy (voltage x current x time) |
| Dependency factors | Only current and time | Voltage, current, and time |
| unit conversion | It needs to be converted into Wh (Wh=V × Ah) based on voltage conversion | Directly represent energy without additional conversion |
| Application scenarios | Measure battery capacity (such as mobile phone battery capacity) | Measuring battery energy (such as electric vehicle range) |
3. Interrelationships
- Conversion formula: Wh=V × Ah
- Example: A 12V, 100Ah battery with an energy of; 12V × 100Ah=1200Wh.
- Meaning: Ampere hour is the foundation of watt hour, but watt hour more comprehensively reflects the actual energy output capacity of the battery.
4. Comparison of application scenarios
- Application of Ah
- Battery capacity labeling: For example, a mobile phone battery labeled as "4000mAh" (i.e. 4Ah) indicates the time it can be discharged at a specific current.
- Current demand matching: When selecting a battery, it is necessary to ensure that its ampere hour value meets the device's current demand (such as drone batteries requiring high ampere hours to support long-term flight).
- The application of watt hour (Wh)
- Energy demand assessment: If the electric vehicle battery is labeled as "60kWh" (i.e. 60000Wh), it represents its total energy and directly affects the range.
- Device power consumption calculation: The operating time of the device can be calculated based on the watt hour value (such as a 100Wh battery supplying a 5W device for 20 hours).
- Air transport restrictions: The International Air Transport Association (IATA) has strict limits on the watt hour value of lithium batteries (such as requiring special approval for exceeding 160Wh).
5. Actual cases
- Mobile phone battery:
- Label "4000mAh" (4Ah), voltage 3.7V, then the energy is; 3.7V × 4Ah=14.8Wh.
- If the power consumption of the device is 5W, the theoretical battery life is; 14.8Wh ÷ 5W=2.96 hours.
- Electric vehicle battery:
- Label "80kWh" (80000Wh), voltage 400V, then the capacity is; 80000Wh ÷ 400V=200Ah.
- If the motor power is 20kW, the theoretical endurance time is; 80kWh ÷ 20kW=4 hours.
6. Summary
- Ampere hour (Ah): measures how much current a battery can release, suitable for comparing battery capacity or matching current requirements.
- Watt hour (Wh): measures how much energy a battery can provide, suitable for evaluating actual range or device power consumption.
- Suggestion for selection:
- When paying attention to battery capacity, check the ampere hour (such as selecting drone batteries).
- When focusing on battery life or energy output, check the watt hour (such as choosing an electric vehicle battery).
- When calculating energy, it is necessary to combine voltage (Wh=V × Ah).
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