Electric Charge: Coulomb's Law, Battery Capacity & Electrochemical Storage
Authoritative guide to electric charge quantization, battery mAh ratings, Faraday electrolysis laws, and SI unit conversions across mobile and automotive energy storage.
Charge Quantization & Coulomb Definition
Electric charge is strictly conserved and quantized in nature. Every observable charge in the universe exists as an integer multiple of the fundamental elementary charge e carried by a proton (+e) or electron (-e):
Total Charge Equation (N = Number of Electrons, e = 1.602176634 × 10⁻¹⁹ C, I(t) = Instantaneous Current)
By integration over time, a continuous current of 1 Ampere flowing through a wire for 1 hour transfers exactly 1 A × 3,600 s = 3,600 Coulombs = 1 Ampere-hour (Ah).
Battery Ampere-Hour (Ah) vs Milliampere-Hour (mAh)
The electrochemical industry utilizes charge capacity to specify battery endurance:
Consumer Electronics: Milliampere-Hours (mAh)
Standard lithium pouch cells for smartphones (3,000–5,000 mAh) and wearable electronics (200–600 mAh). 1 mAh = 0.001 Ah = 3.6 Coulombs.
Automotive & Grid Storage: Ampere-Hours (Ah)
Lead-acid starter batteries (45–100 Ah) and electric vehicle traction packs (100–300 Ah per module). 1 Ah = 1,000 mAh = 3,600 Coulombs.
Peukert's Law & High-Drain Capacity Derating
In chemical batteries, available delivered charge decreases under high discharge currents due to internal electrolyte diffusion resistance. This phenomenon is modeled by Peukert's Law:
Peukert's Equation (I = Discharge Current, t = Discharge Time, k = Peukert's Constant ≈ 1.1 to 1.3)
Discharging a battery at high C-rates delivers less total charge (fewer effective mAh) than a slow, low-drain discharge.