1. What is Battery Capacity?

Battery capacity is the total amount of energy a battery can store, typically measured in ampere-hours (Ah). It determines how long your backup power system can run your essential loads during an outage.

2. How Does the Calculator Work?

The calculator uses the battery capacity formula:

Where:

• Load Power — Total wattage of devices you need to power
• Backup Time — Hours you need the system to run
• Battery Voltage — System voltage (typically 12V, 24V, or 48V)
• Depth of Discharge — Fraction of battery capacity you can safely use (typically 0.5-0.8)
• Efficiency — System efficiency including inverter and wiring losses (typically 0.85-0.95)

3. Importance of Proper Sizing

Details: Correctly sizing your battery bank ensures you have enough backup power while avoiding overspending on unnecessary capacity. Undersizing leads to insufficient backup time, while oversizing increases costs unnecessarily.

4. Using the Calculator

Tips:

• Calculate total wattage of all devices you need to power simultaneously
• Determine how many hours of backup you need
• Use manufacturer specifications for battery voltage
• Typical Depth of Discharge: 80% for lead-acid, 90% for lithium
• System efficiency is typically 85-90%

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between Ah and Wh?
A: Amp-hours (Ah) measure charge capacity, while watt-hours (Wh) measure energy capacity. Multiply Ah by voltage to get Wh.

Q2: How do I account for multiple batteries?
A: For parallel connections, add Ah capacities. For series connections, add voltages while Ah stays the same.

Q3: What's a typical Depth of Discharge?
A: 50% for flooded lead-acid, 80% for AGM, 90% for lithium batteries to maximize battery life.

Q4: How does temperature affect capacity?
A: Battery capacity decreases in cold temperatures - may need 20-30% extra capacity in cold climates.

Q5: Should I add a safety margin?
A: Yes, consider adding 10-20% extra capacity to account for aging and unexpected load increases.