Size your battery pack fast with engineering-grade assumptions. Tune efficiency, reserve and overhead for masses. Download tables as CSV or print-ready PDF anytime now.
| Scenario | Usable Energy (Wh) | Voltage (V) | DoD (%) | Efficiency (%) | Reserve (%) | Specific Energy (Wh/kg) | Overhead (%) | Estimated Mass (kg) |
|---|---|---|---|---|---|---|---|---|
| Small drone | 600 | 22.2 | 80 | 90 | 10 | 220 | 12 | 3.79 |
| Backup UPS | 3000 | 48 | 70 | 92 | 20 | 160 | 18 | 38.05 |
| Light mobility | 12000 | 48 | 80 | 92 | 15 | 200 | 12 | 93.75 |
The calculator first converts your usable energy target into the nominal energy the battery must carry:
Mass is computed from specific energy and then adjusted for pack overhead:
Capacity is estimated by CAh = Epack ÷ Vnom. A simple series/parallel estimate uses cell voltage and capacity.
Start with the energy your load must receive. Enter usable energy in watt-hours, not nameplate capacity. A 12,000 Wh mobility target means 12.0 kWh delivered to the DC bus after conversion losses. If duty is 750 W for 2.5 hours, usable energy is 1,875 Wh. The calculator converts this into required nominal pack energy using margins and losses.
Reserve margin covers cold, aging, and uncertainty. A 15% reserve multiplies energy by 1.15. Depth of discharge limits planned utilization; 80% DoD means dividing by 0.80. Efficiency captures inverter, wiring, and thermal losses; 92% means dividing by 0.92. Together, 15% reserve, 80% DoD, and 92% efficiency scale usable energy by 1.15 ÷ (0.80×0.92) = 1.56.
Specific energy (Wh/kg) converts required nominal energy to cell mass. Typical ranges are 140–180 Wh/kg for LFP, 190–240 Wh/kg for NMC, and 25–45 Wh/kg for lead‑acid. If required nominal energy is 18,720 Wh, cell mass is 18,720 ÷ 200 = 93.6 kg at 200 Wh/kg. Presets are starting points; overwrite them with vendor data.
Packs weigh more than cells. Overhead includes frames, busbars, contactors, enclosure, cooling plates, fasteners, and the BMS. Light packs often add 8–15%, while rugged enclosures can exceed 25%. With 12% overhead, 93.6 kg of cells becomes 93.6×1.12 = 104.8 kg total. Tune overhead to match your mechanical approach.
Capacity is estimated with CAh = Epack/Vnom. At 18,720 Wh and 48 V, capacity is 390 Ah. With 3.7 V, 5.0 Ah cells, series is round(48/3.7)=13s and parallel is ceil(390/5)=78p, or about 1,014 cells. Treat this as planning-level, then refine with voltage limits.
Enable the volumetric check for packaging. At 500 Wh/L, an 18,720 Wh pack is about 37.4 L before mounting space. Use CSV export for trade studies and PDF export for print-ready reviews. Re-run scenarios by changing one parameter at a time to see sensitivity and risk. For quick comparisons, sweep specific energy and overhead to bracket best and worst cases, and document the assumptions used for test temperature, end‑of‑life capacity, and safety margins during early sizing.
Usable energy is what your load receives. The calculator increases it to cover reserve margin, efficiency losses, and a limited depth of discharge so the pack meets the real mission requirement.
Lower DoD means you plan to use a smaller fraction of nameplate energy. To deliver the same usable energy, the nominal pack energy must rise, so estimated cell mass increases.
No. Presets are typical engineering values for quick studies. Use your supplier’s tested Wh/kg at the module or cell level, especially if temperature, discharge rate, or safety features differ.
Start with 10–15% for lightweight consumer designs, 15–25% for robust modules and cooling, and higher for armored or sealed enclosures. Adjust after comparing to similar real packs.
It is planning-level. It uses rounded series count and required amp-hours to estimate parallel strings. Final designs should account for voltage window, cell sag, balancing strategy, and allowable current.
The PDF button opens a print view containing your results table. Use your browser print dialog and choose “Save as PDF” to generate a shareable report.