  To enable electric vehicles (EVs) to access to the internet of intelligent
vehicles (IoIV), charging EVs wirelessly anytime and anywhere becomes an urgent
need. The resonant beam charging (RBC) technology can provide high-power and
long-range wireless energy for EVs. However, the RBC system is unefficient. To
improve the RBC power transmission efficiency, the adaptive resonant beam
charging (ARBC) technology was introduced. In this paper, after analyzing the
modular model of the ARBC system, we obtain the closed-form formula of the
end-to-end power transmission efficiency. Then, we prove that the optimal power
transmission efficiency uniquely exists. Moreover, we analyze the relationships
among the optimal power transmission efficiency, the source power, the output
power, and the beam transmission efficiency, which provide the guidelines for
the optimal ARBC system design and implementation. Hence, perpetual energy can
be supplied to EVs in IoIV virtually.
