batteries

GOOD LORD!!

I have been trying to figure out what kind of batteries to use for my product and have just spent the best part of 2 days trying to figure out and searching trough the Internet at some advise. I had to work this out as i could not go ahead and design my perspex with out the dimensions. Design specifications:

As long life for the smallest amount of space.

I had no idea how you worked out what the battery life is so i trolled through the Internet and found it it was measured in capacitance. the battery i had bought because it was so thin had a 76 mAH life span which is nothing. i have roughly 50 L.E.Ds in each garter all flowing at 20mA meaning each need 20mAH from a battery to work for 1 hour. I found this calculator and put in the values 20 x 50 = 1000 and 500mAH which means a battery of 500mAH would power my L.E.Ds for about 30 mins. i looked at phone batteries, camera batteries but they were all too big. I found these on R.S. being the smallest with the biggest capacitance. I'm putting 2 together to make 6 volts at with 1000mAH at 6.4 mm. not too bad! which should make my L.E.Ds last roughly an hour. WOOOO HOOOO!!