the other day the battery was flat, replaced with new one, still having trouble to start sometimes like there is no power at all, sometimes when driving my car cuts out and headlights dim.

Your alternator could be stuff :) Check the voltage of the battery while the cars running should be about 13v to about 14v :)

by having trouble to start sometimes i mean theres no dash lights like there no battery in there

13.6v runing 13.0v off

Ok then maybe you got a load of some sort while the car is off. Um you will need an amp meter and see if there is a drain on the battery while the car is off.

but why dose it do it some times then be fine and are volt meters ans amp meters the in the same thing?

o and and cuz it loses the volts i have to idle it so it wont stall

Sounds like you have dirty or loose battery terminals or a loose main battery to body/engine earth lead causing an intermitent open circuit between the battery and the car.

and where do i find these main battery to body/engine earth leads ? or just track them back from the terminals?

I used to have a similar problem on my skyline: happened twice

once it was loose terminals

the second time it was the battery. Despite the voltages being right, even double checked by mr nrma, I kept getting stuck when it wouldn't start. I took it to an electrical place, they plugged in a new battery and there was no more trouble.

ok il check them tomorrow