Same here about lack of consistency...I left BOM for SIN 2 months ago on a saturday midnight flight and it took me 3 hours from baggage screening to getting the immigration stamp. Did the same saturday night flight yesterday and 15 minutes after entering the airport I was sitting in the lounge staring at 3 long hours ahead of the flight.

I was carrying AAA batteries (both loose and in my headphones) and had no problems with security.

I was asked to boot up my laptop once on arrival at MAA last year, was waved through with no problems on half-a-dozen pther occasions at BOM and BLR.