Post before yours from Steve K did this. Note use of plural chargers. Expense adds up, plus space, plus cabling, etc. Sure it's an alternative to multi-stage externally regulated alternator, but the benefits seem elusive to me. Why not just setup the correct system in the first place rather than a workaround?
Few TF folks make prolonged runs so having a constant alternator output wouldn't be a problem I suppose. According to the OEM, my Lion Energy LFPs are perfectly happy at 13.9v constant (I must add that their support has been vague and elusive when it comes to anything remotely technical, a stark contrast to other battery builders such as Battle Born who have very specific recommendations).
This thread is far from the first LFP discussion on TF, but has been helpful for me. As Guy With a Boat observed, the future is LFP. An owner can put it off for until the next upgrade cycle, but at some point, not upgrading and adapting the alternator is wasting time and money. Not saying that day is today. But it's damn close. At least that's my observation of typical adoption of new technology as it will apply to house battery banks in cruise-capable boats.
Peter
I don't think it is really a work around. I am not saying its the only way, but one way.
Can you use a LFP as a starting battery? Only if the LFP bank is big enough. So AGM or flooded battery is still needed and needs to be re-charged. Or at lest, for the moment until one is developed. What happens and it not likely but it could, the BMS shuts down with the ALT connected to the house bank. Can the starting bank now be use with the LFP Atl and Reg? If yes, for how long?
Some will say, yes a LFP can be used for cranking. The answer to this question largely depends on the application. But this is a whole other topic!
This way it also protects that Alt since the starting battery is connected to it. Two switches can be installed if the BMS did shut down. One disconnecting the house bank and the other connecting the starting battery to the house loads. In theory, you could run for days until the problem is fixed.
Two years ago when I looked at ABYC rules on this. They wanted a 2nd source, if the BMS did shuts down. But these rules could have changed over time. In other words, running the whole boat off the stating bank to get you home. So the BMS is a factor when buying expansive or inexpensive batteries as Will P. has mentioned.
Oh well, to each his own. And good luck to all on how you setup your system.
Just as a FYI. On BMS, you may want to look at? Can the firmware be upgraded? Can you remote into the battery? Some have a display? Some battery's have a port to communicate with each other which is another topic. As in the Kilolvault battery, there is a port for that but they have not written the firmware to support that yet.