Yes, be careful though, my moped battery is sealed and I put it on a 130 amp starter box without thinking to charge, half hour later POW, acid everywhere.
The voltage needed to charge a battery usually needs to be a little bit over what the rated voltage of the battery is so that the proper reverse chemical reaction can take place. I would aim for maybe about a 14V power source and use a low resistance, high wattage resistor, maybe like .2 ohms or so at 10 watts. If it's working, the resistor will get warm at the beginning of the charge and will cool down as the battery reaches a full charge.
I actually found a schematic online to build a simple battery charger circuit that you connect the battery to, push a button and it automatically charges it and turns off when it's done. I have the parts collected to build it but I haven't gotten around to it yet.
I wish it was easy to revive them. We get rid of a lot of UPS's with 12V, 7Ah batteries in them at work. Usually the battery is so gone that they don't hold enough of a charge to keep the PC powered on when the power goes out.