At the core of the Robot Guitar's pioneering technology is a lithium rechargeable battery system, which takes about 90 minutes to generate a full charge that keeps the innovative self-tuning robotic system going for approximately 200 tunings. Take any quarter-inch guitar cable and plug one end into the adaptor, and the other end into the Robot Guitar. In approximately 90 minutes, the Robot Guitar is ready to go. Use the shortest guitar cable you can find, because the shorter the cable, the less time it takes to charge. You can always check the status of the system's charge by turning the MCK knob to the C position. The LED display will give you a value between 1-10, with 1 being the lowest charge, and 10 being the highest. Rated at 2100 mAh (milli-Amp-hour). Powerpack 2.4 V. 1 Black & Red 4" Wire leads. 1.12 X 2.09 inches.