The MEB OEM CMU's have all the same partnumber, but have firmware flashed onto them that defines working for 12S 156Ahr Meb battery modules or 8S 234Ahr MEB battery modules
Make sure you can tell from what type of donor car you get the OEMcmu's/battery modules, one cannot see the difference from the outside/or partnumber!!! Mixing will create errors or worse

MEB OEM 8S 4port CMU (all ports mandatory connected to MEB 8S battery modules) MAX number MEB OEM CMU connected = 3x 8S CMU's @ 1 GRNbms can-port.
additional unlocked GRNbms can-ports can create larger battery packs.
Largest battery system possible with MEB OEM 8S 4portCMU's = 36 8S MEB battery,limiting factor may be the inverter of choice

MEB OEM 12S 4port CMU (all ports mandatory connected to MEB 12S battery modules) MAX number MEB OEM CMU connected = 2x 12S 4-port CMU's @ 1 GRNbms can-port.
additional unlocked GRNbms can-ports can create larger battery packs.
Largest battery system possible with MEB OEM 12S 4portCMU's = 24 12S MEB battery,limiting factor may be the inverter of choice