I doubt if the radio memory is the problem as they only draw micro-amps to keep the clock and presets going. I would try disconnecting things one at a time and see what happens. Like light switch one week then wipers the next then oher stuff like voltage regulator, alternator etc. One other test you can make is to take a good brand digital multimeter, place the testleads one in (common) and the other on (10 AMPS). There should be 3 or 4 connections to choose from. Rotate the dial to DC AMPS (Most of the junker multimeters from the junker stores will not be capable of this, you need a good one). Then DISCONNECT the battery ground. Connect one lead to the frame of the car and the other to the ground lead. This way you will see how much current is leaking. The display might show a (-) sign in front of the amperage value that just means to swap the leads around to get the correct polarity. DO NOT, I REPEAT, DO NOT place the test leads across the battery from (-) to (+) or you will blow the meter and leads to smithereens. That will short across the battery. Remember to put the test leads back into the common and volts terminals before you put the meter away. I am an electrical engineering tech but I have still blown up the odd multimeter forgetting to do this when I used it again. This is the best way to see what kind of load is draining from your battery. You might need help doing this.
