Li-Ion BMS

Prismatic cells

Structure of a prismatic battery cell

A prismatic Li-ion cell consists of multiple flat-wound, Li-Ion cells enclosed in a plastic case and connected to 2 large terminals.

Shandong HiPower cell anchor

We cut open a Shandong HiPower, 160 Ah, Li-ion, prismatic battery cell. (This cell is similar to a Thundersky / Winston / Sinopoly cell, and to a CALB / Sky Energy cell.)

(Cell courtesy of Peter Oliver of Make Mine Electric.)

The cut-out reveals its internal structure and construction.

Cutout of a prismatic battery cell, edge view cross section shows its structure
Cutout of a prismatic battery cell, side view, cross section shows its structure
Prismatic cell cut-out

The cell consists of:

  • A plastic outer case (possibly PVC)
  • Two sets of flat-wound cells (similar to pouch cells, except not sealed in a bag)
    • Each set has about 24 foils coming out of it, for each of its 2 terminals
    • The negative terminal (shown) uses copper foils; the positive terminal (not shown) uses aluminum foils
    • The foils are 0.05 mm thick (0.002 inches)
  • Two aluminum terminals (only the negative terminal is shown)
    • M8 bolt for terminal connection to the bus bar
    • A 20 mm nut to secure the terminal to the case
    • Internally, the foils are held against the terminal by two clamp pieces, and two sets of screws, washers and nuts
    • It appears that, in this particular cell, the clamp pieces on the negative terminal have dissolved, resulting in heat damage

Across the 51 mm thickness of the cell:

  • 4 mm (8 %): air space for cooling
  • 6 mm (12 %): case
  • 41 mm (80 %): cells

See also: GreenEV's dissection of a HiPower cell

Thundersky cell anchor

Otmar Ebenhoech cut open a Thundersky cell (which apparently had bloated from being fully charged while not constrained).

Again, note that the positive terminal uses copper foils, and the negative uses aluminum.

Cutout of a Thundersly prismatic battery cell
Thundersky prismatic cell cut-out

(Picture courtesy of Otmar Ebenhoech of Cafe Electric.)

© 2008~2014 Davide Andrea. All rights reserved, except where noted by CC mark. Page published on Jun 02 2014. Graphic design by morninglori