As per title drones can be used as a power bank to recharge the drying batteries of sensors.
A drying battery will send a signal to recharge it and the drone will be ready to fly to recharge the battery of sensor by detecting the location of sensor.
The drone can be designed in this way that it can recharge multiple batteries.
The drone can also be designed in this way that the drone can replace the drying batteries with already recharged batteries .but there will be requirements of some changes in the sensors.
We can also designed a Ground vehicle power bank like drone power bank.