Battery Bank Amp Hour Calculator
Determine the amp-hour capacity of your battery system
Battery Bank Amp Hour Calculator
For various battery chemistries and applications
How to Use the Battery Bank Amp Hour Calculator
1. Select a Mode
Use the centered toggle to choose whether you are sizing a new bank from load data or summarizing an existing stack.
- Size from load: Convert Wh or W × time into recommended Ah with DoD, efficiency, and margin controls.
- Estimate existing bank: Multiply module voltage/Ah by series and parallel counts, then compare against a load profile.
- Inline tooltips explain every field, and error/warning banners appear if entries fall outside allowable ranges.
2. Size from Load Workflow
- Pick the energy input type (known Wh or W × time) and enter your load data.
- Choose a standard system voltage or enter a custom LVDC value; chemistry selection auto-fills a DoD that you can fine-tune.
- Adjust total efficiency (0.6–1.0) and design margin (0–30%) to cover inverter losses, temperature, and growth.
- Click Calculate to see Wh, usable Ah, nameplate Ah, the final recommendation, and a continuous current estimate if runtime is provided.
- Need inspiration? Load the sample presets beneath the results card.
3. Estimate Existing Bank
- Enter module voltage and amp-hour nameplate values, then specify series (S) and parallel (P) counts; the calculator derives Vsys and Ahbank.
- Optionally input a load (W) and runtime plus DoD/efficiency targets to see whether the existing capacity meets that profile.
- Warnings flag LVDC stacks above 60 V so you can plan PPE, labeling, and shutdown requirements.
- Use the FAQ and compliance checklist below the calculator for quick references to NEC/IEC design considerations.
IEC / NEC Compliance Checklist
Quick reminders for Article 706 / 480 and IEC stationary battery standards. Always verify with your AHJ.
Applicability
- Modern ESS with inverters and BMS usually fall under NEC Article 706.
- Legacy standby rooms may default to NEC Article 480 procedures.
- Refer to IEC 62485-2 (general safety), IEC 62619 (lithium), and IEC 62933-5-1/-5-2 for ESS guidance.
Listing & Labeling
- Prefer ESS listed to UL 9540; verify UL 9540A data for siting/mitigation on lithium systems.
- Install exactly per manufacturer instructions (NEC 110.3) and keep labels legible.
OCP & Conductors
- Use Icont (when shown) as design current, then apply the 125% continuous-load factor plus derates.
- Select DC-rated breakers/fuses with proper interrupt rating and polarity.
Disconnects & Shutdown
- Provide accessible battery/ESS disconnects and emergency shutdown labeling (NEC 706.15 as adopted).
- Coordinate shutdown controls with inverter/BMS instructions.
Location & Ventilation
- Vented lead-acid banks need ventilation per NEC 480 and IEC 62485-2 gas emission guidance.
- Lithium ESS should meet NFPA 855 spacing, separation, and capacity limits plus any UL 9540A mitigations.
This tool provides engineering aids; final design must satisfy manufacturer instructions, AHJ requirements, and the latest code editions.
How to Calculate Battery Bank Amp Hours
Use these field steps to move from load planning to a bank size you can trust.
1. Gather Load Data
List every device, its wattage, and daily runtime so you can estimate the total energy draw.
- Convert amps to watts when needed (Watts = Volts x Amps).
- Group similar loads like lighting or refrigeration.
2. Convert to Watt-hours
Multiply each device's wattage by runtime (hours) and sum them to get daily Wh consumption.
- Wh Load = Watts x Hours.
- Add surge or startup loads separately.
3. Pick System Voltage
Select the nominal battery-bank voltage (12V, 24V, 48V, etc.) based on inverter size and cable runs.
- Higher voltage lowers current and cable size.
- Match inverter/charge controller ratings.
4. Apply Ah = Wh / V
Divide the total Wh requirement by the chosen system voltage to get base amp-hours.
- Ah (base) = Total Wh / System Voltage.
- Example: 3,600 Wh at 24V = 150 Ah.
5. Account for DoD
Adjust for usable depth of discharge (DoD) and inefficiencies so the bank lasts longer.
- Required Ah = Base Ah / DoD.
- For 80% DoD: 150 Ah / 0.8 = 188 Ah.
6. Size Strings
Determine how many batteries in series (voltage) and parallel (Ah) you need.
- Series adds voltage; parallel adds Ah.
- Example: Four 12V 100Ah batteries = 48V 100Ah (series) or 12V 400Ah (parallel).
Battery Bank Amp Hour Reference Chart
Estimate the amp-hour size needed for common energy targets at 12V, 24V, and 48V.
12V Systems
| Energy (Wh) | Amp-hours |
|---|---|
| 600 Wh | 50 Ah |
| 1,200 Wh | 100 Ah |
| 1,800 Wh | 150 Ah |
| 2,400 Wh | 200 Ah |
| 3,600 Wh | 300 Ah |
24V Systems
| Energy (Wh) | Amp-hours |
|---|---|
| 1,200 Wh | 50 Ah |
| 2,400 Wh | 100 Ah |
| 3,600 Wh | 150 Ah |
| 4,800 Wh | 200 Ah |
| 6,000 Wh | 250 Ah |
48V Systems
| Energy (Wh) | Amp-hours |
|---|---|
| 2,400 Wh | 50 Ah |
| 4,800 Wh | 100 Ah |
| 7,200 Wh | 150 Ah |
| 9,600 Wh | 200 Ah |
| 12,000 Wh | 250 Ah |
Adjust the chart values for your planned depth of discharge and inverter efficiency to size real-world banks.
Battery Bank Amp Hour FAQs
Quick answers to the most common amp-hour and power bank sizing questions.
How many watt-hours is a 20000mAh power bank?
20,000 mAh equals 20 Ah. Multiply by the native cell voltage (typically 3.7 V for Li-ion packs): 20 Ah × 3.7 V ≈ 74 Wh. Expect 10-15% losses when boosting to 5 V USB outputs.
What is 1 Ah equal to?
One amp-hour represents one amp flowing for one hour (3,600 coulombs of charge). Energy is Voltage × Amp-hours, so Wh = Ah × V.
How many hours is a 10000 mAh power bank?
10,000 mAh is 10 Ah. Runtime depends on the draw: Runtime (hours) = 10 Ah ÷ Load (A). A 2 A device would run for roughly 5 hours before conversion losses.
How long will a 20,000 mAh powerbank last?
A 20 Ah bank feeding a 3 A load delivers about 20 Ah ÷ 3 A ≈ 6.6 hours. Real-world runtimes are typically 5-6 hours after accounting for boost and heat losses.
Is 20000mAh power bank 100Wh?
No. 20 Ah at 3.7 V stores about 74 Wh. You would need roughly 27 Ah at the same voltage (or 20 Ah at 5 V) to reach 100 Wh, and FAA limits use the native Wh rating.
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