Battery going bust in 3-4 days

Hi. I have started getting a problem with my Micra for last one month. Two three days everthing is working properly and all of a sudden next day car would not start as the Battery has gone down, I start it with help of other car and then after travelling for 15-20 km that day may be 1-2 days everything will work as normal but again any moment the battery will go down and i am not able to start the car. May be somebody has any idea what may be the problem.

I have 2003 model K12, with keyless go.
Could pop off the live an put a multimeter between the battery and live terminal, checking for parasitic drain.

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An Auto Electrician is your friend, they could check for parasitic drain and test your battery for you; you know some will even do this free of charge.