Started modelling the enclosure and all, here is a little mathematic riddle for you nerds : 
One cells has a diameter of 21mm
The minimum width of the enclosure is 225mm
I want to feet 12 cells parallel to the deck
How do I calculate the angle between each cells using only algeabrae and not geometrie ?
Here is what I did, geometrically, it’s good enough to work with but I’d have loved to find a more mathematical approach :
225 - 21 (that is half the diameter on both side) = 204
204 / 11 = 18.5454 Which is the string at contact point between each circle
and then it’s geometrically immediate to feet them, and I can measure the angle