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Lithium-ion Battery Usable Capacity Formula:
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The usable capacity of a lithium-ion battery refers to the actual amount of energy that can be safely extracted from the battery, taking into account depth of discharge limitations and system efficiency factors.
The calculator uses the formula:
Where:
Explanation: This calculation accounts for the fact that not all of a battery's rated capacity is practically usable due to discharge limitations and energy conversion losses.
Details: Accurate usable capacity calculation is crucial for proper battery sizing, system design, and ensuring reliable power supply in various applications including electric vehicles, renewable energy systems, and portable electronics.
Tips: Enter the battery's rated capacity in Ah, depth of discharge as a decimal (e.g., 0.8 for 80%), and system efficiency as a decimal (e.g., 0.95 for 95% efficiency). All values must be valid positive numbers within their respective ranges.
Q1: What is typical DoD for lithium-ion batteries?
A: Most lithium-ion batteries have a recommended DoD between 80-90% to maximize cycle life, though this varies by chemistry and manufacturer.
Q2: What factors affect system efficiency?
A: Efficiency is affected by charge/discharge rates, temperature, battery management system losses, and inverter/convertor efficiency in the system.
Q3: Why is usable capacity less than rated capacity?
A: Usable capacity is reduced due to DoD limitations (to preserve battery life) and system efficiency losses during energy conversion.
Q4: How does temperature affect usable capacity?
A: Lower temperatures reduce both rated capacity and efficiency, while higher temperatures can increase capacity but may reduce battery lifespan.
Q5: Should this calculation be used for battery sizing?
A: Yes, this calculation is essential for proper battery bank sizing to ensure the system meets energy requirements while maintaining battery health.