Yes, a battery will charge backwards, but it can be revived.
Attach a load such as a headlight sealed beam, and run it down until the light will not burn at all. Polarity on the bulb doesn't matter, it's just a load device to drain the charge. Once the light goes out, connect a charger with the proper polarity observed, and charge the battery at a 5-10 amp rate for several hours. Check the specific gravity every hour or so until there is no difference in the reading for 2 or 3 consecutive checks. At that point, the battery has accepted all the charge it can take. Any further charging just boils water away. Full-charge specific gravity on an automotive battery is somewhere in the 1.265 to 1.300 range, depending on the original strength of the acid and how much loss of plate material off the grids has happened. Some of the capacity of the battery will be lost due to the reversed charge, but I doubt that it will be totally junk unless it was in very bad shape to begin with.
Jerry
