What is the most suitable size of copper wire for car jumper cables?

[Ella]

25 square millimeters is the most suitable size of copper wire for car jumper cables. Because the current is large when starting the engine, the smaller the resistance of the jumper cables, the better. How to use car jumper cables: First, clamp the red wire of the jumper cable to the red positive terminal of the "rescued car's" battery, then clamp the other end of the red wire to the red positive terminal of the "rescue car's" battery; Clamp both ends of the black wire to the black negative terminals of the "rescued car" and the "rescue car" batteries respectively; Start the engine of the "rescue car" first; Then start the engine of the "rescued car". Precautions for using jumper cables: After successfully starting the engine, the jumper cables must be removed in the correct order, otherwise it may cause a short circuit. If the rescued car still cannot start, check whether there is poor contact at the metal connection points.