Ah to VA & VA to Ah Calculator
Convert battery capacity in amp-hours (Ah) to apparent power in volt-amps (VA). This calculator accurately determines VA, watt-hours, and current based on your specified battery voltage and discharge time.
How to Use Ah to VA Calculator
Converting Ampere-hours (Ah) to apparent power (VA) involves processing voltage and operating time.
- 1Enter Battery Capacity. Input the nominal capacity rating of the battery in Amp-hours (Ah).
- 2Enter Battery Voltage. Supply the operating voltage of the battery system in Volts (V).
- 3Enter Discharge Time. Specify the duration over which the battery will discharge, using the dropdown to select either Hours or Minutes.
How to Calculate Ah to VA
Volt-amps (VA) cannot be calculated from amp-hours (Ah) alone. Battery voltage and discharge time are required to complete the conversion. Using standard power principles, we first determine total energy in Watt-hours and then divide by discharge time to find apparent power.
Formulas
Battery Energy (Wh) = Ah × Voltage
Current (A) = Ah ÷ Hours
Example 1
- Battery Capacity: 100 Ah
- Voltage: 12 V
- Operating Time: 10 Hours
Apparent Power = (100 × 12) ÷ 10
Apparent Power = 120 VA
Battery Energy = 100 × 12
Battery Energy = 1200 Wh
Current = 100 ÷ 10
Current = 10 A
Example 2
- Battery Capacity: 200 Ah
- Voltage: 24 V
- Operating Time: 8 Hours
Apparent Power = (200 × 24) ÷ 8
Apparent Power = 600 VA
Battery Energy = 4800 Wh
Current = 25 A
Ah to VA Chart
The table below outlines the apparent power ratings for typical battery capacities and system voltages. Note that these values are based on a standard 10-hour discharge period; actual VA values will change depending on your specific operating time.
| Battery Capacity (Ah) | Voltage (V) | Apparent Power (VA) |
|---|---|---|
| 20 | 12 | 24 |
| 50 | 12 | 60 |
| 100 | 12 | 120 |
| 150 | 12 | 180 |
| 200 | 12 | 240 |
| 100 | 24 | 240 |
| 200 | 24 | 480 |
| 300 | 24 | 720 |
| 100 | 48 | 480 |
| 200 | 48 | 960 |
Note: All values are based on a 10-hour discharge period. Actual values depend entirely on operating time.
How to Convert VA to Ah
To size a battery for a VA load, convert VA to watts with the power factor, multiply by the backup time to get watt-hours, then divide by the battery voltage.
Example: a 1,000 VA UPS load at 0.8 PF for 2 hours on a 24 V battery needs (1,000 × 0.8 × 2) ÷ 24 = 66.7 Ah.
| Load (VA) | PF | Backup (h) | Battery (V) | Required (Ah) |
|---|---|---|---|---|
| 500 | 0.8000 | 2 | 12 | 66.67 |
| 1,000 | 0.8000 | 2 | 12 | 133.3 |
| 1,000 | 0.8000 | 2 | 24 | 66.67 |
| 1,500 | 0.8000 | 2 | 24 | 100.0 |
| 2,000 | 0.8000 | 2 | 48 | 66.67 |
| 3,000 | 0.8000 | 2 | 48 | 100.0 |
Ah to VA Calculator Frequently Asked Questions
To convert Amp-hours to Volt-Amps, you must first calculate the total Watt-hours by multiplying the Ah by the battery's voltage. Since Volt-Amps are a measure of apparent power used in AC circuits, you must also factor in the time duration and the specific power factor of your electrical equipment.
Amp-hours (Ah) measure the total volume of electrical charge stored inside a DC battery. In contrast, Volt-Amps (VA) measure the apparent power flowing through an alternating current system. Converting between the two requires knowing the system voltage and the electrical load's total running time.
Uninterruptible Power Supply (UPS) systems use VA because it accurately reflects the total apparent power the unit can handle, including both usable and wasted power in AC circuits. The internal battery Ah determines the runtime, but the VA rating ensures the internal inverter won't be overloaded.
Batteries themselves do not have VA ratings, as VA is a measurement specific to alternating current systems. However, you can determine how much VA your battery can support over a specific time period by multiplying its Ah capacity by its nominal voltage and dividing by the expected discharge time.
The power factor plays a critical role when matching a DC battery's capacity to an AC load's VA requirement. A lower power factor means your equipment draws more apparent power than real power, forcing your battery to discharge significantly faster to maintain the required electrical performance.
1500VA is the apparent output power rating of the inverter. At a standard 0.8 power factor, it can support a maximum continuous load of 1500 × 0.8 = 1200 Watts.
