Battery Bank Sizing Calculator 🔋
How to Use the Battery Bank Sizing Calculator
Enter daily consumption, battery voltage, days of autonomy (days without sun), and depth of discharge (DoD). Formula: Required Ah = (daily Wh × autonomy days) / (voltage × DoD).
Depth of discharge significantly affects battery lifespan. Lead-acid batteries should not be discharged below 50% (DoD = 50%). LiFePO4 batteries can safely discharge to 80% DoD.
Days of autonomy is your buffer for cloudy days. Off-grid systems typically use 2-3 days. More autonomy means larger battery bank but better resilience.
FAQ
What is depth of discharge (DoD) and why does it matter?
DoD is the percentage of battery capacity you can safely use. Lead-acid batteries should not exceed 50% DoD to preserve lifespan. LiFePO4 batteries can safely discharge to 80% DoD, making them more efficient per Ah.
How many days of autonomy should I plan for?
Off-grid systems typically plan for 2–3 days of autonomy (days without solar charging). In cloudy climates, 3–5 days is recommended. More autonomy means a larger, more expensive battery bank.
LiFePO4 vs lead-acid: which is better for off-grid?
LiFePO4 batteries cost more upfront but last 3–5× longer (3,000–5,000 cycles vs 500–1,000 for lead-acid), have higher DoD (80% vs 50%), and are lighter. Over 10 years, LiFePO4 is usually more cost-effective.
How do I wire batteries for the right voltage and capacity?
Series wiring increases voltage (two 12V batteries in series = 24V). Parallel wiring increases capacity (two 100Ah batteries in parallel = 200Ah). Combine both for higher voltage and capacity.
What battery voltage should I choose for my system?
12V systems suit small loads under 1,000W. 24V systems handle 1,000–3,000W efficiently. 48V systems are best for larger homes (3,000W+). Higher voltage means lower current and thinner wires.