LEDs

Hello
i'm working on a LED circuit, i have 60 white leds in parallel and 2 batteries (6v 4Ah each) in parallel so the power source is 6V 8Ah. i'm lost trying to figure out the resistor i should use to get the circuit working with maximum brightness. and please i need and estimation about the time the batteries will keep working.
NB: electronics is hobby for me so i'm not that experienced.
Best Regards

You need a resistor in series with each group of LEDs.

You get better efficiency if you put several LEDs in series, and put a current-limiting resistor in-series with the group.

You get better efficiency if you connect the two batteries in series and operate from 12V (instead of 6v)

To compute how many LEDs to put in each group, and the current-limiting resistor for each group of LEDs, we need to know the forward voltage drop Vf for each LED, and the desired operating current If for each LED. This info is found on the manufacturer's data sheet for the specific LEDs you are buying.

I got a program of the net to calculate what your looking for.
It will also calculate how long your batteries will last.
Just google 'led pro'.