Battery Management Systems for Large Lithium-Ion Battery Packs
Section 18.104.22.168.err Errata
"The circuit is powered by the cell itself, so it must draw low power (it must draw less current than the leakage of the cells being measured), especially during standby, in order not to discharge the cell;"
add at the end
in order not to discharge the cell... "faster that it would without a BMS".