While this setup will work, it is not the best practice, and not ideal for long term operation. Operating at the cable’s maximum current rating leaves no safety margin, which can lead to excessive heat rise, voltage drops, and premature degradation. While the cable conductor material itself may be rated to easily handle 20A operation, many laser and TEC cables use multi-pin connectors. As a majority of heating occurs at the connection interfaces, users should verify the current rating per connector pin prior to operating at max conditions.
It is also important to consider application needs such as cable length, strain relief, and cable routing when operating at or close to max current ratings. A longer cable will introduce more resistance, which creates a voltage drop from your laser driver to your laser diode. While your laser driver may compensate for the voltage drop, the lost voltage turns into waste heat within the cable. This additional heat stress will not only affect system performance and efficiency, but can cause long term durability concerns. Likewise, proper cable strain relief and routing can significantly improve performance and longevity. A kinked cable leads to additional resistance by putting stress on the cable’s conductor and insulation materials, while coiled cables can introduce resistance, heat, and EMI.
For best results, select a cable that is rated above your controller’s maximum current rating, consider higher current connectors such as a 13W3 D-sub connector or bus bar terminal, and keep cable lengths as short as possible (while remaining practical) to provide as much thermal headroom as possible.