The medium-power controller versions (18v15 and 24v12) are available with the power capacitor and connectors included but not soldered in (as shown in the left picture above) or with the power capacitor and connectors pre-installed (as shown in the middle picture above).
The terminal blocks are only rated for 15 A. For higher-current applications we recommend soldering thick wires directly to the connector-free version of the board and using higher-current connectors (as shown in the right picture above). Another benefit of the connector-free version is flexibility in placement of the power capacitor (e.g. on the other side of the board) to accommodate compact installations or to make room for a heat sink.
The power capacitor has a significant effect on performance; the included capacitor is the minimum size recommended, and bigger ones can be added if there is space. A bigger capacitor might be required if the power supply is poor or far (more than about a foot) from the controller.