I would like to make a simple circuit similar to the zero center ammeter but with LED..
If there is no flow in the current on either side ( ie. when the ammeter is in center ) there will be a GREEN LED which will glow and when there current flow from battery to any load ( ie. when the ammeter shows deflection towards negative side ) there will be a RED LED which will glow and the GREEN LED will go off..
How to design this circuit in and inexpensive way...??
Simply use a bi colored LED and a series resistor. The type with only two connections.
Like this one:-
This was my first idea as well. However this is a pretty crappy current sensor. On the other hand he asked for "cheap" not "good" 
On the other side of the spectrum is this: Current sense amplifier - Wikipedia.
Grumpy_Mike:
Simply use a bi colored LED and a series resistor. The type with only two connections.
Like this one:-
http://uk.farnell.com/dialight/521-9628f/led-3mm-red-grn/dp/1461589
connecting an LED is not a big problem.
But how to sense the amp draw...??
Run the current thru a shunt resistor to create a voltage, as an input to a compator (LM358 for example).
Comparator high output can drive Red LED, low output can drive Green LED.
But how to sense the amp draw.
Current will only be drawn with a voltage drop. It is this voltage drop that the LED and resistor will light with.
If you tell us the nature of the current you are trying to measure then perhaps we can have produce and answer that you can understand.
CrossRoads:
Run the current thru a shunt resistor to create a voltage, as an input to a compator (LM358 for example).
Comparator high output can drive Red LED, low output can drive Green LED.
Hummm thats a good way..
Let me explain the position where the ammeter is connected, it is on a vehicle where the zero center ammeter is connected, when there is a load connected to the battery the ammeter goes towards -ev and when the dynamo is charging the battery the ammeter goes towards +ev..
here is the pic of the ammeter
Now just another thing which came to my mind is make an led bar graph ammeter where 0 is the BLUE LED, the left side will show negative deflection and the right side will show the positive deflection..
here is the picture of how I plan it..
Now if I am using a shunt resistor or a current transformer on the positive terminal of the battery and feed the signal in some sort of led bar graph VU meter IC one IC will be for positive increments another will be of negative decrement, one VU IC will need +ev voltage to increment its output the other VU IC will need -ev voltage to increment..
Please guide me in how to design this circuit...
@Joy
I have an idea here. I was thinking of using a op-amps circuit. Your are using in Automotive, so I will determine the lowest point and the highest point.
Op-amp circuit to calculate and level to 0 to 5 V. The blue LED is 1023 / 2 The program will display the leds using the digital pin or usage of an shift register.
Let see :
-15 V = 0 V
Do you know about this formula : y = m * x + K <--- linear formula m is the multiplication factor and the K is a voltage being added. x is the Vin.
My idea.
I think what you need is a differential amplifier.
Will need to add some DC offset so that the 'zero' point is 2.5V, and it can swing down to 0V for battery draw, and swing up to 5v for dynamo charging.
So if the issue is how to design a suitable circuit I still have to recommend this: Current sense amplifier - Wikipedia. Wikipedia contains links to application notes. One of the applications described there is what the OP requires.
Joy:
I am certain that Mike knows what an Ammeter looks like and that he also knows what a bar graph looks like as well. The problem is that he answered your original question, the one that you posted on the forum, not the question that you really had in mind.
There is a difference between "... a GREEN LED ..." and "... a RED LED ..." (singular, not plural), which is what you asked about and 'several GREEN LEDs' and 'several RED LEDs' which is what you apparently had in mind.
Don