More than likely they are Silicon LEDs; so the voltage drop is 0.7 volts.
If you put them in series instead of parallel, you may not need the resistor at all!
With 12 volts, that would give you 0.8 volts per LED.
Just barely enough to light them. Maybe…
Also, most LEDs can stand up to 20ma (some up to 50ma) without being damaged. Most are happy with 5ma to 10ma…
So if you wanted to try a resistor (with the series setup), start at 600 ohms, and work your way down until you are happy with the brightness…
Also, most 12vdc batteries can vary up to 14vdc (open circuited measurement?) so it may be safer to start with the resistor just in case…
Or another trick is to use a potentiometer (linear preferably), in place of the resistor. Then vary the pot resistance until you are happy with the brightness; remove the pot; measure the resistance; then replace with the closest fixed resistor…
If it turns out that the LEDs are too dark, even with NO resistor at all; then you can try a combination of series/parallel…
Make two groups of LEDs; six (or eight, whatever) in parallel, then the two groups of six in series… Etc… or 3 parallel groups in series, etc…
Chunga, as the site shows, you could use a 3 x 20 array of LEDs with a 120ohm resistor in series with the 3 LEDs and simply have 12v powering them.
And as I told you before, the amperes will kill the LEDs more likely than the voltage would. I should know xD I ran a $2 LED (RGB T_T) at 12v and forget to add a resistor and poof it burned to a crisp with like 200mA running through it =/
lol, thanks robodude, anyway, so theres the information, and i plugged it into the link Beth gave me and it came up with 5 rows of 3 LEDs each, with a 100 ohm resistor at the end of each one (running at 25 mA)
well, off to the mall to fill my Simon mall gift card that doubles as a Visa , cya later
i am not getting the IR LEDs for right now, just normal white 18,000 mcd LEDs and thank for the advice about the IR LEDs, i iwll be sure not to have too many and i will try and keep them sub 8-10 thousand mcd
well, guys, quick update on the LEDs, got a breaboard today and set up wat 1 of the turrents/bar lights will look like on my rover, took some before and after pictures in the dark, its not too impressive, but i think it will be ok
(running at 25 mA)
, cya later
He wants 15 LEDs per PCB! I didn’t notice that. sorry! 
