Designing the right battery bank is one of the most important steps when building a reliable solar PV system. Size it too small, and you will run out of power during cloudy days. Size it too large, and you will overspend on storage you do not actually need.
In this practical, easy-to-follow guide, we walk you through exactly how to size your LiFePO₄ battery bank so your home, RV, cottage, or off-grid cabin stays powered — day and night.
Why LiFePO₄ Is the Best Battery Chemistry for Solar Storage
If you are sizing a solar battery bank today, LiFePO₄ (Lithium Iron Phosphate) is the gold standard, and for good reason.
Benefits of Enexer LiFePO₄ Batteries:
- Up to 100% usable capacity, 80% Depth of Discharge recommended (vs. approximately 50% for lead-acid).
- 3,000–5,000+ cycles for 10+ years of use
- Safe, thermally stable chemistry
- Lightweight and maintenance-free
- Fast charging and perfect for solar PV
- Bluetooth monitoring through the Enexer mobile app
Whether you are going fully off-grid or just want reliable backup power, LiFePO₄ is the smartest long-term investment.
How to Size Your Solar Battery Bank (Step-by-Step)
Step 1: Calculate Your Daily Energy Consumption (Wh per day)
Make a list of every appliance or device you plan to run off solar, such as:
- Lights
- Fridge
- Router
- Fans
- TV
- Laptop
- Water pump
- Phone chargers
- Any additional loads
For each one, multiply:
Wattage × Hours Used Per Day = Watt-Hours/Day (Wh/day)
Example:
- Fridge: 150W × 10 hours/day = 1,500Wh/day
- Lights: 40W × 5 hours/day = 200Wh/day
- Laptop: 60W × 4 hours/day = 240Wh/day
Total Daily Usage = 1,940Wh/day
Enexer Pro Tip: Always estimate slightly higher than you think as solar systems perform best with some buffer capacity.
Step 2: Choose Your Desired “Days of Autonomy”
Days of autonomy is the number of days you want your system to run with no solar input (cloudy weather, storms, winter).
Typical scenarios:
- 1 day for RVs and weekend cabins
- 2–3 days for off-grid homes or cottages
- 3+ days in remote or northern regions
Example (2 days):
1,940Wh/day × 2 days = 3,880Wh (Total Required Energy)
Step 3: Adjust for LiFePO₄ Depth of Discharge (DoD)
Enexer LiFePO₄ batteries allow up to 100% usable capacity however, it is recommended to limit DoD to 80%.
Use the formula:
Required Battery Storage (Wh) = Total Required Energy ÷ 0.80 (DoD)
Example:
3,880Wh ÷ 0.80 = 4,850Wh
This is the minimum usable storage you need from your battery bank.
Step 4: Convert Watt-Hours (Wh) to Amp-Hours (Ah)
Use:
Battery Capacity (Ah) = Required Battery Storage (Wh) ÷ System Nominal Voltage (V)
Common system voltages: 12V, 24V, 48V
Nominal voltages: 12.8V, 25.6V, 51.2V
Example (12V system):
4,850Wh ÷ 12.8V = 378Ah
Step 5: Choose Your Battery Size and Quantity
Now divide your required Ah by the size of the battery you want to use.
Examples:
1. Using 12.8V 100Ah Enexer LiFePO₄ batteries:
378Ah ÷ 100Ah = 3.78 batteries
Round up: you need 4 batteries.
Final Requirement:
4 × Enexer 12V 100Ah LiFePO₄ batteries.
2. Using 12.8V 200Ah Enexer LiFePO₄ batteries:
378Ah ÷ 200Ah = 1.89 batteries
Round up: you need 2 batteries.
Final Requirement:
2 × Enexer 12V 200Ah LiFePO₄ batteries
3. Using 12.8V 400Ah Enexer LiFePO₄ batteries:
378Ah ÷ 400Ah = 0.945 batteries
Round up: you need 1 battery.
Final Requirement:
1 × Enexer 12V 400Ah LiFePO₄ batteries
Step 6: Determine Your Wiring Configuration for Multi-Battery Systems
Parallel and series connections affect your voltage and capacity differently.
Parallel
- Increases capacity (Ah)
- Voltage stays the same
Series
- Increases voltage (V)
- Capacity stays the same
Example:
- For a 12V 100Ah system: all 4 batteries wired in parallel for 400Ah total
- For a 12V 200Ah system: all 2 batteries wired in parallel for 400Ah total
Enexer Pro Tip: Always match your:
- Inverter voltage
- Charge controller voltage
- Battery bank voltage
Quick Reference Formula
Use this formula to size your battery bank quickly:
Battery Bank Size (Ah) = (Daily Load (Wh) × Days of Autonomy) ÷ (System Nominal Voltage × DoD)
Where:
- DoD for LiFePO₄ = 0.80
- System nominal voltage = 12.8V, 25.6V, or 51.2V
Enexer Pro Tips for Perfect Solar Sizing
- Choose LiFePO₄ for the longest lifespan and highest usable capacity
- Use a solar charge controller that supports lithium iron phosphate battery profiles
- Keep wiring distances short to reduce voltage drop
- Plan expansion space if you will add solar panels later
- For large systems (3kWh+), get a professional design review
Power Your Solar System with Enexer
Whether you are upgrading an RV, installing a home backup system, or building a full off-grid cabin, Enexer offers reliable, high-performance LiFePO₄ batteries built to last.
Shop Enexer LiFePO₄ Batteries:
https://www.enexertech.com/collections/solar-pv-energy-storage-batteries
Need help sizing your battery bank? Our experts are ready to help:
https://www.enexertech.com/pages/contact
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