well , assuming it is working and you do not want to hack into it the only solution is to get a 12v DC to 120V AC inverter and just plug it in. Of course you will need hefty cabling from the battery. But really this is not a good option.
The other option is to open it up and connect wired directly to the woofer and use a normal car sub amp....
However.. your results may not be good. Car subs are much smaller and roll off below because they take advantage of car interior cabin gain. Home subs go much lower.
But home subs are not made for the hot cold and humidity and vibration in cars... you may ruin it quickly..
To be perfectly honest, having done lots of car audio, Just look out for used gear and get a proper car sub and amp...
Maybe someone wants to swap with your sub.
Ed