battery-capacity-dat

• 18650-dat - 26650-dat

battery test

2. Example for a Typical Li-ion 26650 (5000 mAh)

• Discharge Current: 0.5 A (500 mA)
• Expected Capacity: 5000 mAh Time = 5000 mAh ÷ 500 mA = 10 hours

3. Practical Notes

• Cutoff Voltage:
  
  • Li-ion NMC/NCA: ~2.5–3.0 V
    
  • LiFePO₄: ~2.0–2.5 V
    
• Temperature: Test at room temp (~25 °C) for rated results.
• CC Test: Your tester should log voltage & time; capacity is the area under the discharge curve.

Car Sedan Lead-Acid battery

• lead-acid-battery-dat

• Typical Voltage (V): 12 V

• Typical Capacity Range (Ah): 40 Ah to 70 Ah

Calculating Energy (Wh) = Voltage (V) × Capacity (Ah)

• Minimum Energy: 12 V × 40 Ah = 480 Wh
• Maximum Energy: 12 V × 70 Ah = 840 Wh

So, the energy stored in a typical car lead-acid battery is usually between 480 Wh and 840 Wh.

20000 mAh * 3.7V

Energy (Wh) = 20 Ah × 3.7 V = 74 Wh

2.6Ah * 12V

Energy (Wh) = 2.6 Ah × 12 V = 31.2 Wh

1000 Wh

1000 watt-hours (Wh) == 1 度

Runtime = 1000 Wh / 5V * 1A = 1000 Wh / 5W = 200 hours

quick calculation

2000 mAh = 2 Ah Runtime ≈ (2 Ah * 3.7 V * 0.85) / (1 A * 5 V) ≈ 1.26 hours

for 20000 mAh, == 12.6 hours

Calculating Runtime for a 2000mAh Power Bank Supplying a 1A @ 5V Device

Here's a breakdown of how to estimate the runtime:

1. Power Bank Energy

• Capacity: 2000 mAh (milliampere-hours) = 2 Ah (ampere-hours)
• Nominal Voltage: 3.7 V (typical for lithium-ion/polymer batteries)
• Total Energy (Watt-hours, Wh): Capacity (Ah) × Voltage (V)
  • 2 Ah * 3.7 V = 7.4 Wh

2. Device Power Consumption

• Current: 1 A (ampere)
• Voltage: 5 V (standard USB output)
• Power Needed (Watts, W): Current (A) × Voltage (V)
  • 1 A * 5 V = 5 W

3. Efficiency Consideration

Power banks are not 100% efficient when converting their internal battery voltage (3.7V) to the required 5V output. Energy is lost, primarily as heat, during this conversion.

• Estimated Efficiency: Let's assume an average efficiency of 85% (or 0.85). This can vary between 80% and 95% depending on the quality of the power bank circuitry.

4. Effective Energy Available

This is the amount of the power bank's stored energy that can actually be delivered to the device after accounting for conversion losses.

• Effective Energy: Total Energy (Wh) × Efficiency
  • 7.4 Wh * 0.85 ≈ 6.29 Wh

5. Calculate Runtime

• Runtime (hours): Effective Energy Available (Wh) / Device Power Consumption (W)
  • 6.29 Wh / 5 W ≈ 1.26 hours

Conclusion

A 2000mAh, 3.7V power bank can theoretically supply a device drawing 1A at 5V for approximately 1.26 hours, or about 1 hour and 15 minutes.

Disclaimer: This is an estimate. Actual runtime depends on factors such as:

• The precise efficiency of the specific power bank.
• The age and health of the battery cells.
• The quality of the charging cable (resistance losses).
• Ambient temperature.
• Whether the device's power draw is constant or fluctuates.

ref

• Lead-acid-battery-dat