12 Volt Electric Wire - Length and Current

Maximum length of copper wire with 2% voltage drop

Maximum one-way length for two conductor copper wire from power source to load in a 12 volt system with 2% voltage drop is indicated below:

Wire Length - feet

12 volt copper wire maximum length

Wire Length - meter

12 volt copper wire maximum length

  • double the distance if 4% loss is acceptable
  • multiply distance by 2 for 24 volts
  • multiply distance by 4 for 48 volts

Example - Maximum Length of Wire

The current to a light bulb with power 50 W be calculated with Ohm's law

I = P / U

  = (50 W) / (12 V)

  = 4.2 A

From the diagram above the maximum length should not exceed approximately 8 m for wire gauge #10 (5.26 mm2). By increasing the size of the wire to gauge #2 (33.6 mm2) the maximum length is limited to approximately 32 m.

Related Topics

  • Electrical - Electrical units, amps and electrical wiring, wire gauge and AWG, electrical formulas and motors

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