Drummie, with those voltages I agree the rectifier sounds faulty, but that does not explain why the battery discharges so quickly, The only thing that makes sense is the faulty rectifier has damaged the Battery and its capacity is shot. I would replace the rectifier, I would go solid state, and try another borrowed battery for a brief test. Otherwise I agree with Julian, you have a wire that is earthing out. If you want an original rectifier I like many have taken off a working rectifier.