Lithium batteries

Hi.

I have detailed the installation in two other threads but in essence the start and bow thruster batteries are AGM and the charging for these is unchanged from factory install that is for alternator and mains charger. The Lithiums are connected to, and isolated from,  this side of the system via two DC-DC chargers. These chargers present themselves to the alternator and mains charger as just another load and so there is no need for any communication.  The DC-DC chargers take whatever voltage the alternator supplies and raises or lowers this to meet the charging needs of the Lithiums these have a charge profile for the lithiums and so dont communicate with the BMS. They are 'intelligent' in that they detect when the engine is not running and disconnect so that the start battery isn't discharged.  This replaces the standard automatic battery combiner. The solar charger is connected direct to the Lithium bank and doesn't charge the AGMs.  There is no communication needed between the solar charger and the DC-DC chargers.  The BMS has no need to communicate with the other systems and is also stand alone and is only used for active balancing of the cells and detecting fault or over current conditions.  There is a wiring diagram in my threads

The reason for upgrading this way was to minimise the physical changes and minimise the costs.  its been working well with the exception of the mains charger that cant provide sufficient current for the Lithiums with both DC-DC charges running.  One is switched off when on mains.  

If building a system from scratch in a new boat this wouldn't be the best approach to be honest. 

Hope that helps.