dear battery wont run down just because of the hazard signel , and if some how it discharges then it can charge with in 30 min while you run your car , its totally wrong that its goes off just because of that , may be it already have completed its life , but the second thing is that you new battery also goes off .............. there is some problem with your alternator/generator ,,,,,,,,,,,,,,do your self a test to check the alternator ,,,,,,,,,start the engine ,,,,,,,,,,,,,,after that remove one of the battery terminal while some one sitting on driving seat and foot on gas peddle , if your car switches off as soon as you remove the terminal then it means your alternator is not working ,,,,,,,,if wont then switch on the head light ,,,,,,,,if the light is ok and no effect in RPM then it means your alternator is also ok ,,,,,,,,,,,,,,,
further alternator/battery test can be done with an amp meter ,