Hello guys.
I was in the same situation a month ago, and after my first top balance discovered that the cells can swell up a lot, for example, this cells use to sit perfectly flat, and this happened after a low C rate charge, a couple of mm of separation:
Its not that bad and its between spec, but aside from the recommendation from EVE of adding pressure, the nordkyn desing web also recommends a fixture to prevent "delamination" from the expansion / contraption cycles.
Cells are probably going to be OK with, or without it..., but i invested a lot of $$ on my system and want to make it last as long as possible. So if i can spend a couple of days and some dollars to make a fixture and just maybe get 500 - 1000 more cycles, ill do it.
This is some solutions from marinehowto and nordkyn desing:
Very easy to make, only problem would be the heat disipation that migh drecrease the lifespan a little bit (Probably neglilible with our lower C rates)
I decided to make a full enclosure:
- Have aluminum flatbars and "T" extrusions to allow some airflow betwen cells, so heat wont be much of a problem.
- Can mount both horizontallly and vertically, also could fix to the wall.
- Can "easily" transport the full pack to connect between systems. (Probably not needed for a lot of people, but usefull for me).
- Can easily change the BMS, as the leads are connected to a connection bar.
- Looks better!
And as you can see, i have 4 x threaded rods in the design, so i can put the 300KGF if i want, in practice i just compress them a bit as i dont know how to calculate or measure that... i guess you can calculate that with a torquimeter or just measure with a pressure plate.
The cell walls stay completely flat with the middle flatbars and resistant aluminum structure in both sides.
So far im happy with the build!