There are many restrictions on bringing batteries on board the ISS, so cords to connect to the power source are a necessity.
The voltage drop experiment aims to check "how much the voltage drops” when we pass electric current through a cord connecting KIROBO to the ISS. Generally, when electric current flows, voltage drops in relation to the distance. This is an attribute of electricity which occurs anywhere, not only in space. Even with general electric cables on Earth, the possibility of a voltage drop rises as the cable becomes longer.
The distance from the window to the power source in the ISS is six meters. For KIROBO to go to the window, a voltage drop experiment for a six-meter cord was necessary. ”To show KIROBO Earth” is the wish of the development staff.
It was discovered that when an electrical current of 5V was passed through a six-meter cord, the voltage reaching KIROBO was down to 4.1V. The voltage required for KIROBO to operate is 5V. To allow a margin, the supply voltage was raised to 7.5V. With this extra 2.5V, we can show you the same Earth that KIROBO sees.