If you design this transformer, who is going to make it. If you need one, go to a transformer manufacturer or supplier, he will sort you out. If you are designing the charger, just start with the secondary winding and do the rest. It would be helpful if you said what voltage lead acid battery you are designing for. So sort out the voltage required, then the current required. Figure out how you are going to achieve this. Work out what sort of transformer secondary voltage you require - allow for the incoming mains to be on the low side. Go to a transformer manufacturer or supplier to see what the nearest commercial unit available is. It is not practical to wind you own mains transformer.
Frank