🔋 Battery Life Calculator

Estimate runtime for phones, laptops, drones, solar systems, and any battery-powered device

For mAh/Ah, voltage is required
For mA/A, voltage is required
Required when using mAh, Ah, mA, or A units
⚙️ Advanced Options
%
Typical: 85-95%
%
100% = full discharge

📊 Estimated Runtime

3.15 Hours
3h 8m
Hours : Minutes
0.13
Days
Battery Capacity: 5000 mAh
Power Draw: 5 W
Battery Energy
18.5
Wh
Energy per Hour
5
Wh/h
Current Draw
1351
mA
Efficiency Loss
10
%
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🧮 How Battery Life is Calculated

Runtime (hours) = (Battery Capacity × Efficiency × DoD) ÷ Power Consumption
For Watt-based consumption: Runtime = (Capacity in Wh × Efficiency % × DoD %) ÷ Power in Watts

Unit Conversions:

1 Ah = 1000 mAh 1 Wh = 1 Ah × Voltage
1 kWh = 1000 Wh 1 Wh = 1000 mWh
1 W = 1000 mW 1 kW = 1000 W

Example Calculation: A 5000 mAh battery (3.7V) with 5W power consumption:

  • Convert to Wh: 5000 mAh = 5 Ah × 3.7V = 18.5 Wh
  • Apply 90% efficiency: 18.5 Wh × 0.9 = 16.65 Wh
  • Runtime = 16.65 Wh ÷ 5W = 3.33 hours = 3h 20m
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📱 Device Battery Life Examples

📱

Smartphone

4000 mAh, 2W usage ~7.4 hours
4500 mAh, 3.5W usage ~4.7 hours
5000 mAh, 2.5W usage ~6.7 hours
💻

Laptop

50Wh, 15W usage ~3.3 hours
100Wh, 30W usage ~3.3 hours
80Wh, 20W usage ~4.0 hours
🔋

Power Bank

20000 mAh, 10W charging ~7.4 hours
26800 mAh, 18W charging ~5.5 hours
30000 mAh, 15W charging ~7.4 hours
🚁

Drone

5000 mAh, 100W usage ~11 minutes
2000 mAh, 80W usage ~5.5 minutes
10000 mAh, 150W usage ~15 minutes
☀️

Solar System

5kWh, 500W usage ~8.5 hours
10kWh, 1000W usage ~8.5 hours
2kWh, 300W usage ~5.7 hours
🚗

Electric Vehicle

60kWh, 15kW usage ~4.0 hours
100kWh, 20kW usage ~5.0 hours
75kWh, 18kW usage ~4.2 hours
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❓ Frequently Asked Questions

What's the difference between mAh, Ah, and Wh?

mAh (milliamp-hour) and Ah (amp-hour) measure charge capacity. They tell you how much current a battery can deliver over time.

Wh (watt-hour) measures energy capacity. It takes voltage into account: Wh = Ah × Voltage.

Example: A 5000 mAh (5Ah) battery at 3.7V has 18.5 Wh of energy. mAh is simply 1/1000 of Ah.

Why is real battery life shorter than calculated?

Real-world factors that reduce battery life include:

  • Voltage drop - Batteries don't maintain exact voltage
  • Heat - Higher temperatures increase internal resistance
  • Battery age - Capacity decreases over time
  • Device efficiency - Power conversion losses
  • Background processes - Apps and services consume power

Use 80-85% efficiency for more realistic estimates.

How do I calculate battery life for solar systems?

For solar systems, use:

  • Capacity in kWh (kilowatt-hours)
  • Power in kW (kilowatts)

Also factor in:

  • Depth of Discharge - Lead-acid: 50%, Lithium: 80-100%
  • Inverter efficiency - Typically 85-95%
  • System losses - Wiring, temperature, etc.
What is depth of discharge (DoD)?

Depth of Discharge (DoD) is how much of the battery's capacity you use before recharging.

  • Lead-acid batteries: 50% DoD (using more shortens lifespan)
  • Lithium-ion batteries: 80-100% DoD (can use almost full capacity)

Higher DoD = more runtime but shorter battery lifespan.

Can I use this for EV battery calculations?

Yes! For electric vehicles:

  • Use kWh for battery capacity (e.g., 60 kWh Tesla Model 3)
  • Use kW for power consumption (e.g., 15 kW highway driving)
  • Formula: Runtime = Battery kWh ÷ Power kW

Example: 60 kWh ÷ 15 kW = 4 hours of driving (about 240 miles at 60 mph).

How accurate is this battery calculator?

Our calculator provides mathematically precise results based on:

  • Battery capacity and voltage
  • Power consumption
  • System efficiency (adjustable)
  • Depth of discharge (adjustable)

For best accuracy, measure actual power consumption with a watt meter and adjust efficiency based on your device.