Battery Energy (Wh) vs. Capacity (Ah): What's the Difference?

When choosing a lithium battery, many buyers focus on its Ah rating. However, Ah alone does not tell you how much energy a battery can store.

Understanding the difference between Wh and Ah helps you choose the right battery for your solar and ESS applications.

1. Battery Energy (Wh)

Wh measures the total electrical energy stored in a battery.

Formula: Energy (Wh) = Voltage (V) × Capacity (Ah)

For example:

• 12V × 100Ah = 1.2kWh

• 24V × 100Ah = 2.4kWh

• 51.2V × 100Ah = 5.12kWh

• 102.4V × 100Ah = 10.24kWh

The same Ah rating can represent different energy capacities depending on battery voltage.

2. Battery Capacity (Ah)

Ah measures the amount of electrical charge a battery can deliver.

Formula: Capacity (Ah) = Current (A) × Time (h)

For example, a 100Ah battery can theoretically supply 10A for 10 hours or 20A for 5 hours.

Actual performance depends on discharge rate, temperature and battery operating conditions.

3. How Does Discharge Rate Affect Battery Performance?

Higher discharge currents can cause greater internal voltage drop and reduce usable capacity.

Therefore, when selecting a battery, it is important to consider not only its rated capacity but also its continuous discharge current and power capability.

4. What Should You Check When Choosing an ESS Battery?

Always consider these key specifications:

• Nominal voltage (V)

• Rated capacity (Ah)

• Total energy (kWh)

• Usable energy and DoD

• Continuous charge and discharge current

• Cycle life

Conclusion

Remember:

• Ah measures electrical charge capacity.

• Wh / kWh measures stored electrical energy.

• Voltage × Ah = Wh.

At KOODSUN, we manufacture LiFePO4 batteries and provide low-voltage, high-voltage and complete ESS solutions for residential, commercial and industrial applications.

KOODSUN – Reliable Battery Solutions for a More Sustainable Future.