Choosing the Right Battery Capacity for a 5kVA Inverter

When selecting the appropriate battery capacity for a 5 kVA inverter, it is crucial to consider several key factors including the inverter's output voltage, desired backup time, and the load you intend to power. This guide will walk you through a step-by-step process to help you determine the necessary battery capacity.

1. Determine Load Requirements

Identify the total wattage of the appliances you plan to run, which should be based on the maximum input rating of the inverter, typically around 5000 watts for a 5 kVA inverter, assuming a power factor of 1. Take into consideration whether you need to support only continuous loads or if peak loads are also a factor.

2. Calculate Battery Capacity

Most inverters operate at 12V, 24V, or 48V. Check your inverter specifications to determine the optimal voltage. Knowing the desired backup time and applying the correct formula can help you calculate the required battery capacity in amp-hours (Ah).

Formula:

Battery Capacity Ah (Total Load W × Backup Time h) ÷ Battery Voltage V

Example Calculation

Total Load: 4000 watts
Inverter Voltage: 48V
Desired Backup Time: 4 hours

Calculate the capacity:

Battery Capacity Ah (4000 W × 4 h) ÷ 48 V
Approximately 333.33 Ah

3. Consider Battery Efficiency and Depth of Discharge (DoD)

Ensure you take into account the efficiency of both the inverter and the battery. A typical inverter efficiency ranges between 85-90%. If using lead-acid batteries, it is advisable not to discharge them below 50% to maximize their lifespan. Lithium batteries can tolerate higher DoD without compromising performance.

To adjust the capacity for efficiency and DoD, you can modify your initial calculation as follows:

Example: If we desire to account for 90% efficiency and a DoD of 50%, the adjusted capacity would be:

Adjusted Capacity Ah 333.33 Ah ÷ (0.9 × 0.5)
Approximately 740.74 Ah

Conclusion

To summarize, for a 5 kVA inverter with a load of 4000 watts and a backup time of 4 hours, the required battery capacity would be approximately 740 Ah at 48V, when accounting for efficiency and DoD. Make sure to adjust your calculations based on your specific load, inverter voltage, and desired backup time.

Understanding these factors will help ensure a reliable and efficient power system for your home or business.