  We investigate a multi-qubit quantum battery-charger model, focusing on its
potential emulation on a superconducting qubit chip. Using a large-spin
representation, we first obtain the analytical form of the energy $E_B(t)$,
power $P_B(t)$ and their maximum values, $E_B^{\rm max}$ and $P_B^{\rm max}$,
of the battery part by means of the antiferromagnetic Holstein-Primakoff
(AFM-HP) transformation within the low-energy approximation. In this case, our
results show that superextensive scaling behavior of $P_B^{\rm max}$ ensues. By
further combining these with the ones obtained via exact diagonalization (ED),
we classify the dynamics of various physical quantities, including the
entanglement between the battery and charger parts for system sizes
encompassing over 10,000 qubits. Finally, by checking a diverse set of system
configurations, including either a fixed battery size with growing number of
charger qubits, or when both parts simultaneously grow, we classify the system
size scalings of $E_B^{\rm max}$ and $P_B^{\rm max}$, relating it with the
entanglement entropy in the system. In agreement with the analytical results,
robust superextensive behavior of $P_B^{\rm max}$ is also observed in this
case. Our work provides an overall guide for expected features in experiments
of quantum batteries emulated in superconducting qubit platforms, in particular
ones that exhibit long-range couplings.
