Hello asad!
buddy i have faced the same problem couple of days ago, like dim interior lights and with sound system lights flicks, now i have installed a nissan generator of 100ahs with bolt on fit, as the daewoo's original is of 65 ahs, now my problem is solved, no fluctuation at all as the generator is boosting 100ahs, in automobiles the generator capacity should be greater than the installed battery capacity. go to ahata mitho khan in madina market, i purchased it through a reference in Rs. 1500/- only without giving the old generator back.
regards