Battery Size Calculator
Calculate required battery capacity or runtime for your applications
Calculate Battery Requirements
Power consumption of your device or appliance
Different battery types have different discharge characteristics
Nominal voltage of your battery system
How long you need the battery to power your application
Recommended: 50% for lead-acid batteries
Input Error
Application load must be greater than 0
Common Application Examples
LED Light (10W)
Power: 10 W
Voltage: 12 V
Duration: 8 hrs
Laptop (65W)
Power: 65 W
Voltage: 19 V
Duration: 4 hrs
Desktop PC (200W)
Power: 200 W
Voltage: 12 V
Duration: 2 hrs
Refrigerator (150W)
Power: 150 W
Voltage: 12 V
Duration: 24 hrs
Electric Fan (75W)
Power: 75 W
Voltage: 12 V
Duration: 6 hrs
Router/Modem (15W)
Power: 15 W
Voltage: 12 V
Duration: 24 hrs
Battery Type Comparison
Lead-Acid
• Lower cost per Ah
• Discharge to 50% max
• Heavier and bulkier
• Complex discharge curve
Lithium-Ion
• Higher energy density
• Discharge to 20% max
• Lighter and compact
• Linear discharge curve
Common Battery Voltages
Typical Power Consumption
Battery Sizing Tips
Add 20-30% safety margin to calculated capacity
Consider temperature effects on battery performance
Account for inverter efficiency losses (10-15%)
Plan for future expansion of your system
Understanding Battery Sizing
Basic Concepts
Battery sizing involves determining the minimum capacity needed to power your applications for a desired duration. The calculation depends on power consumption, voltage, duration, and battery type.
Key Formulas
Load Current
Current = Power / Voltage
Lithium-Ion Capacity
Simple linear discharge
Lead-Acid Capacity
Accounts for Peukert effect
Important Factors
Depth of Discharge (DoD)
Maximum safe discharge level varies by battery type
Peukert Effect
Lead-acid batteries lose capacity at higher discharge rates
Temperature Impact
Cold temperatures reduce available capacity
Aging Effects
Battery capacity degrades over time and cycles
Example Calculation
Scenario:
- • Power a 200W device for 4 hours
- • Using 12V lead-acid battery
- • Keep 50% charge remaining
- • Temperature: Normal (25°C)
Calculation:
- • Load current: 200W ÷ 12V = 16.67A
- • Peukert factor: (0.02 × 4 + 0.6) = 0.68
- • Required capacity: (100 × 16.67 × 4) ÷ (50 × 0.68)
- • Result: ≈ 196 Ah battery needed