AddCAP 820 is an add-on capacitor unit designed to enhance battery power supply for drive systems using low-impedence electric motors (1-2 turns). It should also be used when the wires from your battery to your ESC need to be lengthened more than 20cm (8 inches). 
In case the wires are longer, use one AddCAP 820 for each 20cm (8 inch) section. Another advantage of adding an additional capacitor is to reduce possible interference which may be caused by current moving through your power wires. Recommended for use with 2.5-6 mm2 (14AWG – 10AWG) wires.