Are you saying the battery goes dead afgter it sits idle for a couple of days or are you using it daily and it still goes dead? Are you sure the alternator is actually charging? Even if the alternator is in perfect condition, it might not charge if wiring is not good. Does the alternator light work in instrument panel? Light should be on with key on and engine off. And it should be off while engine is running. (pretty basic stuff, but you would be amazed at number of people that don't know it) If the bulb is blown, it can cause some alternators not to charge, they rely on complete circuit to ground through the light bulb. If you have a voltmeter, see what voltage is at the batteries when engine is running 1500 rpm or so. You should see 13.5 - 14.5 volts. If it is charging properly, then you either have a drain on the system or a bad battery. Even a new battery can be bad. If you have one battery, disconnect the negative terminal and look for a spark when you disconnect and reconnect the cable. If you see a spark, you have a drain on the system. The most common place to see a drain is in the alternator. Disconnect the alternator and see if the spark goes away. Let us know what you find out, and then we can go further if needed.