  With the rapid development of quantum science and technology, quantum
batteries have also emerged. However, there are still many unresolved issues in
the field of quantum batteries. For example, how to improve battery space
utilization, maximize battery energy storage, and how to increase and control
the charging power of quantum batteries. A major challenge is how to achieve
better charging power without reducing the energy storage of the quantum
batteries. Here, we propose a controllable dual-cavity quantum battery which
can increase the charging power without diminishing capacity of the quantum
batteries by manipulating the number of atoms . This control method can
effectively adjust the charging power of quantum batteries from $N^2$ times to
$N^2.5$ times, and even to $N^3$ times. By adjusting the number of atoms,
quantum batteries can achieve theoretical "fast charging" and "slow charging".
