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DC voltage drop
Include both copper conductors and temperature.
HB3YAQ · Ajdin HadzicLearning to take awayhttps://hb3yaq.ch/en/tools/voltage-drop
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Formula & context
R = ρ₂₀[1 + α(T − 20)] · 2L/A; ΔU = I · R; P = I²R
One-way distance is doubled for outgoing and return conductors. The model uses approximate copper values ρ₂₀ = 0.0175 Ω·mm²/m and α = 0.00393/K.
A worked example
3 m, 2.5 mm² and 10 A at 20°C give about 0.42 V drop and 4.2 W cable dissipation.
Assumptions & limits
Does not size ampacity or protective devices. Contacts, fuses and connectors add resistance in practice.
Voltage drop in supply wiringUnderstand the reasoning →From reading to experimenting
DC voltage drop
3 m, 2.5 mm² and 10 A at 20°C give about 0.42 V drop and 4.2 W cable dissipation.
Open example with starting values →Supply voltage: 13.8 V · Current: 10 A · One-way cable length: 3 m · Copper cross-section: 2.5 mm² · Conductor temperature: 20 °CBack to the learning article →Then change exactly one value. Compare the result and use the formula to explain why it changes. The model limits below the calculator also apply here.