Results will appear here
Enter your battery sizing inputs, submit the form, and the calculator will place the complete result block here above the form.
Calculator Inputs
The page stays single-column overall, while the calculator fields use a responsive 3-column, 2-column, and 1-column grid.
Example Data Table
| Required Wh | Voltage (V) | Efficiency (%) | DoD (%) | Reserve (%) | Temp (%) | Recommended Ah |
|---|---|---|---|---|---|---|
| 500 | 12 | 92 | 90 | 10 | 100 | 55.92 |
| 1200 | 24 | 95 | 95 | 10 | 100 | 61.56 |
| 2400 | 48 | 95 | 90 | 15 | 95 | 72.42 |
| 300 | 12 | 85 | 50 | 20 | 90 | 81.70 |
| 1500 | 36 | 92 | 80 | 10 | 98 | 64.24 |
Formula Used
1) Base amp-hours:
Base Ah = Required Wh ÷ System Voltage2) Effective usable fraction:
Effective Fraction = Efficiency × DoD × Temperature Factor × (1 − Reserve Margin)3) Recommended installed battery bank:
Recommended Ah = Required Wh ÷ (System Voltage × Effective Fraction)4) Installed battery energy:
Installed Wh = Recommended Ah × System VoltagePercent values are converted to decimals before calculation. For example, 95% becomes 0.95 and 10% reserve becomes 0.10.
How to Use This Calculator
- Enter the energy demand in watt-hours.
- Enter your battery bank or DC bus voltage.
- Pick a chemistry preset or keep manual values.
- Set efficiency, discharge limit, reserve margin, and temperature factor.
- Optionally add average load and the Ah rating of one battery unit.
- Press Calculate Capacity to show the result block above the form.
- Review the graph, check the recommended bank size, and export the report as CSV or PDF.
FAQs
1) What is the difference between Wh and Ah?
Wh measures stored energy. Ah measures charge capacity. Voltage connects them, which is why the same Ah rating stores very different energy at different system voltages.
2) Why does the calculator need voltage?
Voltage is required because amp-hours alone do not describe total energy. The conversion from watt-hours to amp-hours is simply energy divided by voltage.
3) Why is the recommended Ah larger than the base Ah?
The base result ignores losses and operating limits. The recommended bank includes efficiency loss, discharge restriction, temperature derating, and reserve capacity for safer real-world sizing.
4) What does reserve margin mean here?
Reserve margin is the portion of battery capacity you intentionally avoid using. It improves reliability, extends cycle life, and gives headroom during unexpected demand spikes.
5) Are the chemistry presets exact?
No. They are practical starting points. Manufacturer data, temperature range, aging, and discharge current can change the real values, so adjust the fields when you have better specifications.
6) Can this help size solar or backup batteries?
Yes. It is useful for solar storage, UPS systems, telecom backup, RV batteries, marine banks, and other DC energy-storage designs that start with an energy requirement.
7) Why does temperature factor reduce capacity?
Many batteries deliver less effective capacity in colder conditions. The temperature factor models that reduction so the recommended battery bank is not undersized in real operation.
8) What does the parallel battery estimate show?
It estimates how many equal-capacity battery units are needed in parallel to meet the recommended Ah target at the selected system voltage. Series design is assumed to be handled separately.