Off-Grid Storage Design

Off-Grid Battery Bank Sizing Calculator

Solar cabin sizing, marine long-range cruising electrical design. Calculates total required Amp-hour capacity for an off-grid system to survive consecutive cloudy days without solar production.

Off-Grid Battery Bank Sizing Calculator
Watt-Hours (Wh)
Days
Volts
Ratio
Calculated Result
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Instant Calculation
Auxiliary Value
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Engineering Output
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Step-by-Step Derivation ▼ Show Steps
Governing Formula Verified Physics
Bank Ah = (Daily Wh × Days of Autonomy) / (System Volts × DoD × Efficiency)

Calculations adhere to standard electrical equations and National Electrical Code guidelines.

Engineering Principles & Calculations

This calculator uses the exact mathematical relationships between Daily Energy Consumption (Wh/day), Days of Autonomy (1-3 days), System Voltage (12/24/48V), Battery Chemistry (AGM / LiFePO4) to determine Required Battery Ah, Number of Parallel/Series Batteries, Total Weight Estimate. In practical applications, electrical systems must account for safety derating factors, nominal vs actual voltages, and conductor resistance losses.

Calculates total required Amp-hour capacity for an off-grid system to survive consecutive cloudy days without solar production.

Typical Application & Best Practices

Solar cabin sizing, marine long-range cruising electrical design.

Reference Matrix

Off-Grid Battery Bank Sizing Calculator Benchmark Lookup Table

Daily Wh UsageDays of Autonomy12V Bank Ah24V Bank Ah48V Bank Ah
1,000 Wh/day1 Day116 Ah58 Ah29 Ah
2,400 Wh/day2 Days556 Ah278 Ah139 Ah
4,000 Wh/day2 Days926 Ah463 Ah232 Ah
6,000 Wh/day3 Days2,083 Ah1,042 Ah521 Ah
FAQ

Frequently Asked Questions

What does 'Days of Autonomy' mean? +
Days of autonomy refers to how many days your battery bank can power your electrical loads continuously with zero solar input (such as during heavy cloud cover or rain).
Should I build a 12V, 24V, or 48V battery bank? +
For systems under 1,500W, 12V is fine. Between 1,500W and 3,000W, 24V is significantly more efficient. Above 3,000W, 48V is the industry standard to prevent massive cable sizes.
Why factor in Depth of Discharge (DoD)? +
Discharging batteries to 100% causes premature cell death. Lead-acid should only be discharged to 50%, while LiFePO4 can be discharged to 80-90%.

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