Peter
OK, first, your BMS is not doing its job.
The primary job of a BMS is to disconnect the battery if any of the individual cells go lower or higher than what the settings are, and / or the cells get too cold or too hot (heat not usually an issue for LFP / LiFeO4). So if one of your cells went below 2.5V it should have disconnected the whole pack, and then none of your cells should have went to 0V.
There is a unique problem with a BMS that disconnects the propulsion battery on a boat, it isn't hard to figure out. It is for this reason that I do not have a BMS on my boat. I have a settable low voltage relay that controls a big 300 amp relay to disconnect the batteries when pack voltage gets too low, along with a 300 amp circuit breaker to bypass this relay in emergency situations. My solar chargers and shore power chargers are set to stop charging when voltage gets too high, and I don't do regen, yet. And I don't have any temperature protection.
There are 2 main types of BMS; 2 port and 3 port. The 2 port one only has two big connections (one to battery, the other to the load), the 3 port one has three big connedtions (one to battery, one to the load, the third one to the charger). The 3 port one with the separate charger lead should keep the load connected while disconnecting the charger when fully charged. If you have a 3 port BMS you should make sure that you don't have the charge and load ports swapped.
Some BMS's also balance charge the cells. This usually happens by sending current from the highest voltage to the lowest voltage cell. Most BMS's balance charge current is very small and most of them try to balance all the time. Balancing all the time can be a problem, if your battery gets low then it will drain itself and should cut off.
LFP batteries do not usually need to be balanced while being used because the voltage variance should be very small. Other Lithium Ion batteries (not LiFeO4) do need to be balanced while being used because they can have larger voltage variance and can potentially shut down prematurely if one cell drops below settings due to voltage sag while being used.
I think a lot of people now think that "top balancing" is the best way to go with LFP batteries (check out "off grid garage" on youtube), but to do this you need a BMS that can be programmed to only balance when the voltage gets up to a certain voltage. Most BMS's don't have this programing capability, but most have the capability for the balancing to be turned off and on with an accessory switch.
This start balancing voltage will vary according to who or what you believe but should be above 3.2V (working voltage) and obviously below 3.65V (max voltage). I use 3.4V start balancing and only charge to 3.6V my two 48V -100Ah packs.
In my opinion, the balance charging current for a BMS that has balance charging is usually only good for small Ah batteries (like 50Ah or less). Some people use a separate piece of equipment to balance charge, this is what I do. I used to have a 5 amp passive balance charger and I had to install a switch to turn it on and off, or it would just drain the battery. Now I have a 1 amp active balancer (made by Daly) on each battery pack. I am not a Daly fanboy at all (most of their stuff fails more or at least as much as anything else) but I tried one of their 16s 1 amp Smart Equalizers because I saw a few reviews that people were happy with them on their 48V-300Ah battery packs. The "Smart" ones have Bluetooth. The first one worked well enough that I bought another one. That was a year ago and I am still happy with them.
When you start fooling around with low voltage (3-4V) batteries you HAVE to get a meter that reads out to 2 decimal places. 3.2 volts is not good enough, 3.24 volts IS good enough, 3.249 volts is even better (but a 3 decimal place meter is quite pricey).
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