webfootguy
100 W
To avoid overtighting and physical stresses on the joint between cells and to maintain contact, I would highly recommend use of "spring washers" between cells that are joined end to end. Also known as "Belleville Washers" or "Belleville Springs" or "Disc Springs". The idea is a washer that is curved so it attempts to flatten out as you tighten it down. It tries to return to its curved shape thus maintaining tension. If there is physical stressing of a cell (vibration or hitting a bump) it goes into compressing the spring more rather than breaking something. I suppose if your cell holders are rigid enough, this is unnecessary.
--phil
--phil