It doesn't matter how much you "pack the cells very tight", there's a geometrical limit here.[1] And in practice, you'll have modules of sections of the batter

It doesn't matter how much you "pack the cells very tight", there's a geometrical limit here.[1] And in practice, you'll have modules of sections of the battery for repairing which drops the efficiency to below 90%. [1] https://en.wikipedia.org/wiki/Circle_packing#Densest_packing https://en.wikipedia.org/wiki/Circle_packing#Densest_packing