This is blatantly false, unless you are confusing battery for an assembled battery pack. In EVs each battery management IC can run somewhere in the range of 4-14 cells in series per chip, and they almost universally run banks of up to 100 cells in parallel. For example, in the tesla model s the pack is comprised into submodules of 76 cells in parallel and 6 of those groups in series per management chip--so only one management chip per 456 cells.