new transformer,battery--but battery wont charge??

I have replaced my battery and my transformer. (the old transformer actually melted somewhat and the plastic case was sagging down in the outlet)--all was perfect until a day later and the error code came up--low battery?? Somehow the battery is not charging--is there anyone who knows how to fix the charging part of the circuit board--I have a duplicate, extra circuit board--but fear that If I transfer all lines to it, I will lose my code # and I do not know how to enter a new code???