Since this group has provided me with the soundest advice I am coming back for some more, on a similarly related issue dealing with balancing my 16 Eve 3.2v 280 ah LifePo4 batteries. I purchased a dc power supply as advised. Charged the cells to 3.27, give or take, and then put the 16 cells in parallel. That was 10 days ago.? Put the dials at 3.7v and 3.52 ah. They are all now at 33.09v after 10 days, although the two end batteries are 3.10v. That is probably fine as it goes but here's the issue I need advice on: The batteries have not advanced from the 33.10/33.09 for over a day now. Every day before this the battery voltage would increase only a few tenths of a volt, but there was a steady increase. However, with no increase in the last 24 hours I am wondering if they are topped out, despite what I'm reading and seeing from others that they should be balanced to at least 3.5v. Any ideas why they might be "stalled" or are they topped out? Should I just patiently wait a little longer to see what happens or does no change in the last 24 hours mean they are topped out and ready to go? Thanks for whatever ideas you have.

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Peter

3.65V is 'full' for LFP cells.? By bringing all your cells to that voltage (usually in parallel), you're more sure they are at the same energy level (assuming capacity-balanced cells).? This approach is referred to as 'top-balancing'.

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The problem with 3.2V is that's on the very flat part of the charge/discharge curve for LFP chemistry.? You could be at 20% SOC or 40% SOC, depending on very small voltage differences that would all read as 3.2V on a not-very-precise-or-accurate meter.

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There is also an approach called bottom-balancing, which I've never used, that tries to achieve the same result by starting at 0% SOC (or some other very low number).? I don't like bringing cells down that low (it can be hard on them), and it's not as well-defined of a voltage (2.5V, 2.75V, ...?).? 100% SOC is easy to know you're at, based on the cells not accepting further charge beyond just a trickle (C/100 say).

Peter,
Another possible failure point (there are many different types of failure points): each battery connection. Make sure each connection to each post of each battery has the same high amperage surface contact area, the same cleanliness, the same torque value on the nuts or bolts, the same operating temperature, the same washers, the same lug count, etc. The basic concept is that you are trying to drain and charge each battery identically. If one of the posts has a higher resistance to electricity flow (dirty, loose, wavy washer, different size washer, wavy lug, worse crimping of the battery cable to the lug...) that post will run hot, which changes the internal resistance of the battery, which further exacerbates the imbalance, which further drains that battery, which can quickly and permanently change the internal chemistry of the battery.
Most of the time, these slight imbalances amount to a hill of dry beans (dry beans self-level pretty well). But if you cook the beans, the hill of beans can be significant.
The BMS was telling you to stop, in a language that assumed you were an electrical engineer with deep knowledge of LiFePO4 battery chemistry. Sometimes safety requires us to kill the batteries to save the boat, so the nice thing about your BMS is that it let you kill some batteries to save yourselves.
One really helpful simple tool is a $30 temperature gun. A more expensive but automated option is to install calibrated temperature probes on each battery terminal, and feeding that information to a BMS that would alert you to temperature imbalances.
One gallon of diesel compares to roughly 40 kWh of energy. You have roughly 4 kWh in your fully charged healthy 16 battery pack (4,480 under perfect conditions, which they never are). But your e-propulsion is ideally about 5 times more efficient than diesel. This means your 4 kWh pack, times 5 for efficiency, equals 20 kWh diesel power equivalent. So going out with your (16) 280Ahr batteries fully charged is like leaving the dock with 1/2 gallon of diesel fuel. You could go really slow (~1 knot) for ~10 hours, or really fast for ~10 minutes, but then the batteries need charging. Your 2200EU generator allows you to travel at ~1 knot continuously if the generator is running continuously. These are very approximate water speed estimates, not GPS speeds, and are influenced by literally hundreds of variables about your sailboat, the sea state, the weather, people moving around on your boat, etc.
This is the ballpark you are playing in. It is not an argument for or against e-propulsion, just the current state of electricity storage and creation.
My arguments for e-propulsion are:
low operating cost
low maintenance
low stink
low sound
low space requirements
low emissions
high reliability
high precision of thrust
high thrust available

high longevity
high tech
high investment in a better tomorrow
The hard part: e-propulsion often comes with a high learning curve. Many of our ancestors died during the learning curve of gasoline, but they gifted us cultural wisdom about the dangers of gasoline. We are gifting our progeny with the cultural wisdom of clean energy use. Don't kill yourself in the process: each battery can be lethal.

Thanks Jerry, Gives me hope. I just might try that. I have a couple that are below 2, as well. First it was the #6 module, then #5 went, and #12 went about the same time as #5. Do you have the link for that DC power supply you got?