Battery Pack Clamping and Enclosure Concept

As covered in the 'Holding and Compressing Expanding Cells' post, the enclosure needs to provide firm retention of the cells, and constant force clamping, while the cells expand and contract.

Here is concept:
  From bottom to top:
  • Sliding tray with battery enclosure made of 3/16" aluminum
  • 6mm cork sheet for thermal insulation (will add heating pads in the box later)
  • 1/8" lauan plywood for cell sliding during expansion and for thermal insulation
  • Clamp based on 2 3/8" aluminum bookend plates, pressed together via 1/4" rods (the white plastic tubing prevents the rods from rubbing against the cells)
  • 1/4" Poron compression pads
  • 20 LF280 cells (4S5P)
  • Plastic bumpers (add'l precaution to prevent cells from moving up in case of a rollover or massive bump)
  • Plastic sheet for electrical insulation (in case the cell terminals or busbars get anywhere close to the lid)
  • 3/16" aluminum lid
The top and bottom lips on each bookend are bent with a brake. They increase rigidity, and the lower lip is used to secure the bookends to the tray with M6 bolts. But first the cells, pads, bookends and rods will be assembled and compressed on the bench. Only then will this whole assembly be placed inside the enclosure and bolted down.
 
With this layout, each cell within a 5-cell stack should stay in the same position as it expands and contracts, allowing the use of rigid busbars.
 
Another option is to position the foam pads only at the bookends:
2 pads on each side should provide enough expansion room and linear compression. That layout provides excellent thermal contact between the 5 cells within a stack, thus balancing temperature better across cells.
 
However, the distance between 2 adjacent cells' terminals (~1.2mm) will now change as the cells expand and contract. So rigid busbars might not be ideal here. Also, additional taping may be needed on the cell cases for abrasion resistance against vibrations.

In any case, simple enough, let's get to the doing ! Although, I can't help wondering if this might be too much thinking / work / cost ? Maybe wood screws and zip ties would have been sufficient and super safe ? 😂
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