Electric charge is measured in coulombs. Battery capacity uses ampere-hours (Ah) — both are units of charge.
What Is Charge?
Charge (Q) is carried by electrons. 1 electron = 1.602 × 10⁻¹⁹ C. 1 C = charge of ~6.242 × 10¹⁸ electrons. Current = charge flow rate: 1 A = 1 C/s.
Charge Units
- 1 Ah = 3,600 C
- 1 mAh = 3.6 C
Phone battery: 3,000–5,000 mAh. Car battery: 40–100 Ah.
Battery Capacity
A 3,000 mAh battery at 3.7 V stores 11.1 Wh. If your phone uses 2 W, it lasts ~5.5 hours.
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Frequently Asked Questions
How do I convert mAh to coulombs?
Multiply mAh by 3.6. A 5,000 mAh battery = 18,000 C.