We recommend a maximum cable impedance of 0.4 ohm. Although resistance would be the more fitting designation, as a measured impedance always depends on the applied frequency.
For the cable however, the length of the cable is more interesting than the applied frequency. The longer the cable, the greater the resistance of the cable. For 2.5 mm² you have a resistance below 0.4 ohm up to a length of 15 metres. The resistance will become greater as of this length.
As soon as you choose a larger cable cross-section (e.g. 4 mm²) as of this length, you will keep the resistance below 0.4 ohm.
For the cable however, the length of the cable is more interesting than the applied frequency. The longer the cable, the greater the resistance of the cable. For 2.5 mm² you have a resistance below 0.4 ohm up to a length of 15 metres. The resistance will become greater as of this length.
As soon as you choose a larger cable cross-section (e.g. 4 mm²) as of this length, you will keep the resistance below 0.4 ohm.