Why are batteries rated in mAh instead of Wh?

mAh intuitively connects to current × time (2000 mAh battery, 500 mA consumption → ~4 hours). But Wh is more accurate for energy comparison. Laptop batteries are usually rated in Wh.

How many Coulombs is 1 Ah?

1 Ah = 3,600 C. The Coulomb is too small for battery engineering, so Ah/mAh are used instead.

Electric Charge Unit Conversion | Eng Unit Converter

Electric Charge Conversion Guide

Electric charge quantifies the amount of electricity transported by a current over time: Q = I × t. The SI unit is the coulomb (C), where 1 C = 1 A × 1 s. In battery engineering, ampere-hours (Ah) and milliampere-hours (mAh) are the practical units. Key conversions: 1 Ah = 3,600 C, 1 mAh = 3.6 C. Energy stored in a battery: E(Wh) = Q(Ah) × V. A 5,000 mAh battery at 3.7 V stores 18.5 Wh = 66,600 J. Charge measurement is vital in battery engineering (capacity rating), electrochemistry (Faraday's law: 1 mole of electrons = 96,485 C), capacitor design (Q = CV), ESD protection, and power electronics. Common pitfalls: comparing mAh across batteries with different voltages (mAh is charge, not energy — use Wh for fair comparison), assuming a 10,000 mAh power bank delivers 10,000 mAh at 5V output (internal cells are typically 3.7V, so usable capacity is ~7,400 mAh before efficiency losses), and confusing Ah (charge) with A (current).

! Electric Charge — Good to Know

mAh is charge, not energy. Energy (Wh) = Charge (Ah) × Voltage (V). Never directly compare mAh of batteries with different voltages.
A "10,000 mAh" power bank is usually rated at internal cell voltage (3.7V). At USB 5V output: 10,000 × 3.7/5 = 7,400 mAh, and accounting for ~90% conversion efficiency, actual usable capacity is about 6,600–6,700 mAh.

Electric Charge

Electric Charge Conversion Guide

! Electric Charge — Good to Know

Frequently Asked Questions