Electrical & Engineering5 min read
Battery Backup Runtime: Hours of Power From Your Battery
Runtime = usable Wh × inverter efficiency ÷ load in W. A 12 V 100 Ah battery at 90% efficiency and 150 W lasts 7.2 hours, but only 3.6 if half is usable.
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- Electrical & Engineering5 min read
Battery Capacity in Ah and Wh: What the Rating Means
Battery energy in Wh = nominal volts × amp-hours: a 12 V 100 Ah battery holds 1,200 Wh. Convert mAh, compare packs and learn the 100 Wh flight limit.
- Electrical & Engineering5 min read
Capacitive and Inductive Reactance Formulas
Xc = 1 ÷ (2πfC) and Xl = 2πfL. At 50 Hz a 1 µF capacitor is 3,183 Ω and a 100 mH inductor is 31.4 Ω. See how both change with frequency.
- Electrical & Engineering5 min read
How Much Energy Does a Capacitor Store?
Stored energy E = ½ × C × V². A 1,000 µF capacitor charged to 12 V holds 0.072 J, and doubling the voltage quadruples it to 0.288 J.
- Electrical & Engineering5 min read
Watts to kWh: Electrical Power and Energy
Power is volts × amps and energy is power × time. A 230 V, 8.7 A heater draws 2.0 kW, so 3 hours uses about 6 kWh. Costing it explained.
- Electrical & Engineering5 min read
Wire Resistance from Resistivity, Length and Area
Resistance R = ρ × L ÷ A. A 20 m copper run of 2.5 mm² (ρ = 0.0175 Ω·mm²/m) measures 0.14 Ω one way, or 0.28 Ω there and back.
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