🔋 Battery Life Calculator

Calculate how long a battery will last based on capacity and current draw

📏 Input Parameters

Battery Capacity (mAh)

Current Draw (mA)

Efficiency (%)

📊 Results

Battery Life

16.0 hours

Days

0.67 days

📚 Understanding Battery Life

How Battery Life is Calculated

Battery life depends on the battery capacity (measured in mAh or Ah) and the current draw of your device. The basic formula is simple, but real-world factors affect actual runtime.

Formula

Battery Life (hours) = (Capacity in mAh / Current Draw in mA) × Efficiency

Capacity: Total charge stored in the battery (mAh)
Current Draw: Average current consumption (mA)
Efficiency: Typically 80-90% due to losses

Factors Affecting Battery Life

Temperature: Cold reduces capacity, heat accelerates degradation
Discharge Rate: Higher currents reduce effective capacity
Battery Age: Capacity decreases over time
Battery Chemistry: Li-ion, NiMH, alkaline have different characteristics

Tips to Extend Battery Life

Reduce current draw through efficient design
Use sleep modes when device is idle
Optimize software to minimize active time
Choose appropriate battery chemistry for your application

Frequently Asked Questions

Why is my actual battery life less than calculated?

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Real-world factors like temperature, discharge rate, battery age, and inefficiencies reduce actual runtime. The efficiency factor (typically 80%) accounts for some losses, but extreme conditions can reduce it further.

What is a good efficiency percentage to use?

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Use 80% for general estimates. For high-quality batteries with moderate discharge rates, you can use 85-90%. For high discharge rates or poor conditions, use 70-75%.

How do I measure my device's current draw?

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Use a multimeter in series with the battery to measure current. For variable loads, measure over time and calculate the average. Consider using a USB power meter for USB-powered devices.