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Interconnecting two banks

I'm in the planning stages of converting my 46' sailboat to a Victron Lithium system. Most of it (in the stern) is pretty straightforward: 3x12v Lithium Smart 160 Ah with BMS connected to a Victron Multi 200w (or 300w, but that's not the issue) charger/inverter and two solar arrays connected through Smart Solar 100/20 MPPT controllers.

The "interesting" part is in the bow, where there is a 12v windlass drawing 100A (fed with a 2/0 from the house batteries) and bow thruster running on 24v. Currently there is a 12v AGM and a relay which puts the battery in parallel with a (separate) 4/0 feed from the house bank for charging and in series with the house bank for running the thruster (I didn't design it; it was installed by the previous owner!).

What I'm planning is to put two Smart 160 Ah in place of the single AGM and tie the two big cables together for a low-resistance charging feed (overkill, I think) and allow these two to function as part of the house bank in normal operation.

This would be an obvious "no problem" with AGMs, but would I be endangering my batteries in such an install, or should I add battery protectors or something else to keep the two banks balanced? Raising the anchor or running the thruster to dock would draw down a max of abourt 20 Ah, but that would be 15% of the two forward batteries' capacity. Almost always the 100A alternator (with a LiFePO4 program) would be running when this is happening.

Thanks in advance!

Walt Knowles
Braesail -- Moody 46

Battery Balancer
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