How to find a Battery Drain... short to ground
1. Get a 12v. light bulb that has wries on both ends, (a bulb in a wired socket) I use a trailer clearance light.
2. disconnect the ground cable from the battery
3. dissconnect the positive cable
4. connect the light in line bewteen the postive battery terminal and the positive cable.
5. reconnect the negative battery cable.
NB: while you have them off, examine and clean if necessary.
It is OK for the bulb to glow, but if it shines, there is a short.
The brighter it shines the greater the draw, or drain.
There is always a slight drain on the battery for things like Keep Alive Memory for the computer, radio presets, car alarm, remote starter etc. hence the glow is OK.
6. start pulling fuses, when the light goes out (or rather just down to a glow) you found the circuit that the short is in.
7. If pulling fuses doesn't work, then pull relays, and finally the connections to the alternator.
NB: you'll have two sets of fuses and relays. One set under the hood in the power distribution box, and another under the dash, usually driver's side.
NB: different color fuses are different amperages, and should not be interchagned!
Your owner's manual should have a diagram depicting what items are protected by which fuse.
Once you have narrowed the problem down to a particular circuit, start examining the wiring going to the components. See if any are frayed and contacting metal, try to eliminate sections, by disconnecting connectors, switches, bulbs etc.