Hi..Hopefully I can help..If your battery is continually draining "seeing as a new one has been fitted" then you'll have what's termed as a parasitic battery drain which is usually a component within the car drawing current from the battery whilst the ignitions off or the car is un used.. Seeing as i would asume you had the charging system checked out aswell as all earth points.ensuring the terminals are tight etc.then the next step really is to test to see which circuit is at fault..
When cars ignitions off is check all exterior lights "including number plate lights which are always missed out" and interior lamps , glove box "if any"/ boot lights are not still on when the cars not in use or locked or any other items plugged in make sure it disconnected also check on any aftermarket fitted accessories are properly wired in..
After that's done - The only other test that can be done usually - is you will need to be checking the electrical draw the battery has on it when the car is locked up, with the key in the "off" position". and the doors locked wait 15 minutes roughly, then disconnect the battery cable on the negative/earth side. Attach a test light/ digital multimeter between the negative battery cable end and the negative battery terminal. The test light should illuminate extremely dimly or not at all. If the test light is on brightly or quite bright there is a sign there is an electrical draw in the system. To locate you will need to start removing and refitting fuses "one" at a time so you'll need to be careful which ones you pull so you'll need to refer to the manual each time or the lid and start of with the known ones first in particular as far as the fuse(s) for those bulbs/lights and work your way through them and keep referring the the testlight/multimeter etc to see any change. if or which ever fuse is removed and the test light goes out or voltage drops on multimeter the circuit in question has been located . You will need to identify that pulled fuse and what it covers within the car and that should be where the parasitic drain is on that circuit either a faulty component or a wiring fault on that particular circuit which will need tracing and investigated carefully..It does take a bit of time to check all that.but that's usually the next step on this one....I do hope this helps..If you to ask anything else or include further info then just continue before you rate