Outdoor siren + quick release battery + power supply v2

Hi,I’ve just bought the outdoor siren + a quick release battery + power supply v2 and now I am reading that this battery will only charge via a solar panel? Is this a joke?Is there a way to charge “continuously” the battery with the power supply so the battery take over in case of temporary power cut ?Also, do you suggest to leave the 3 D batteries as well in such setup?PS: the power supply will be plugged to an indoor plug (there is a hole in the wall so the power cable can be plugged at the back to the outdoor siren)Thank you.