12v source? how many led? Xitanium driver?

[kingkong]

hi,

I have a 12volt battery source? how many led(cree or soul) can i place in series?
3.7 + 3.7 + 3.7 = 11.1 (3 leds)
12 -11.1 = 0.9
0.9/.7 = 1.2ohms

Does this look right?

I also have a Xitanium ( input 120v 0.8 amp, out put 12v min 0.8am max 5amp)
how should i drive the leds? 6 cree LED in serialas?

Thanks,
cuong.