I’m building a prop for my children’s band performance this year. I built a box that will conceal a drop down cloth panel. I’m trying to open the door remotely to reveal the panel by it rolling down. I bought an electrimagnetic door closer and it works, but it’s powered by a 12v 23amp battery. The magnet has to be on to keep the door closed and turned off to open the magnet/door. The issue is that the small battery only last about 7 minutes pushing current to the magnet, which isn’t nearly enough time for the band to get on the field and perform before the battery goes dead, revealing the panel and ruining the show. I need an alternative that will keep the magnet closed at least an hour and be controlled by remote, so the band director can open the door and reveal whenever she wants. Any help would be greatly appreciated.