The method Idaman describes definitely works - BTDT.
However, some batteries are just flat no good. Some have shorted cells or other problems. This method, by fooling the charger, will put a charge on a battery that's bad enough that the charger had rejected for safety reasons.
So here's the warning. Do NOT do this without closely supervising the batteries while they change. Because it is a fire hazard. I have had internally shorted batteries get so hot they started to smoke.
Also, if after receiving a partial charge, then being charged solo, the suspect battery still gets rejected by the charger, just throw in the towel and get rid of it.