I've been sitting in traffic 2-3 hours playing music full blast (bosè system) and charging my iPhone. Is that enough to mess up the battery. The car died in traffic on 3rd attempt started back up. FYI new powerful heavy duty battery fitted 3-4 months ago. 

 

But I noticed today for first time with this car 3-5 times while not moving in traffic the rev dial will drop suddenly towards 0 then shoot back to 1 and settle what could that mean? (P.s same day car went dead in traffic I think due to playing music full blast for 2-3 hours in traffic)

 

my mate suggesting alternator dying?

Had my friend run a computer over it. He said its charging at 1300 something amps/volts so alternator fine. He believed the fault lied with the battery 12v 8amps Hal battery hsb096 I purchased four months ago. I got the store on my friends advise to replace the battery for a new one and I'll see how it goes. 

 

I would always advise buying a battery of reasonable quality 'always get the best you can for your budget'.

There are plenty of cheap ones which will let you down, but a quality one will generally weigh more than the cheap one .... one reason, more lead content, hence better quality.

Four months ago the weather was warmer so not too much load on the battery. Now the weather's cold and dark, you'll have heater, wipers, seats, headlights, HRW all running the same time probably so this is what can happen with a cheap battery.

If it wasn't cheap (e.g. around £40 - £45) I would take it back and compare it to a more expensive one and see what you differences you find afterwards.

Cheers  Trevor

really common this time of year for batteries to die