How can I add a coulomb counter/current meter to ADBMS1818?

It should support 80V (80/18s) and 100 Ampere. There is a 100 ampere limit for discharge, there is no limit for charge.

You can use ADBMS2949 or else you can use ADBMS2950B (which will need extra SPI port since it is not compatible with ADBMS1818) for coulomb counting. ADBMS2950B is the newest product with the newest features and simplified software design. 

If you want all of the systems to work together and  ADBMS6830B (18 cell IC which can balance all cells at once upto 300mA per cell) and ADBMS2950B (pack monitor for coulomb counting) + ADBMS6822 (isoSPI comm IC) would be the ideal combination. 

You can use ADBMS2949 or else you can use ADBMS2950B (which will need extra SPI port since it is not compatible with ADBMS1818) for coulomb counting. ADBMS2950B is the newest product with the newest features and simplified software design. 

If you want all of the systems to work together and  ADBMS6830B (18 cell IC which can balance all cells at once upto 300mA per cell) and ADBMS2950B (pack monitor for coulomb counting) + ADBMS6822 (isoSPI comm IC) would be the ideal combination.