All lithium batteries have a BMS that monitors individual cells. The difference is if, or how, the BMS communicates with the outside world. The worst option is a drop-in battery with no outside communication. As has been indicated on forum posts, while this is fine for non critical applications such a camper trailer, many feel it is unacceptable for a yacht where an unexpected battery shutdown could be saftey issue.In a recent teaser MG have said that only Lithium batteries with the cells having individual BMS should be used in the marine environment, this is consistent with the advice given on Lithium threads here. However it is also said that Blue Tooth is inadequate (the last word is mine). They say that the BMS should be hard wired (the implication is that some batteries offer Blue Tooth to communicate (am I showing my total ignorance? ). I assume the recommended hard wiring is to displays and to Blue Tooth
Much better and usually only slightly more expensive is a drop-in battery with Bluetooth communication. This allows the operator to monitor individual cell voltages and provides a warning that the battery is about to shut down.
Better again is a lithium battery with wired external communication. This can be done (to a certain extent) with a DIY battery, but if purchasing a commercial battery generally this is a more expensive option available from companies such as Mastervolt and Victron. The big advantage is that this communication allows for the automatic shutdown of charging devices if approaching a HVD event. This lessens the chance that the house battery system will suddenly disconnect. Whether the extra cost and complexity is justified depends on the circumstances.