Is it possible to charge a stereo with a battery at low voltage? Can it be charged?

1, charging is possible, but can not be charged. It's like two pools of the same height, who can't be high, but who can't be low;

2, the device is also able to work, but the charger power is still not enough for the speakers to be put directly, especially when the volume is high and the bass is heavy, it's obvious that the sound is very muffled. So long-term use of this will lead to battery over-discharge, easy to damage the battery;

3, if there is an electric car battery is best, directly to the top. Because this speaker is also 12V battery powered.