Here's my "boilerplate LFP House banks" summary, mostly from marine electrics discussion forums involving long-term users and professionals, with special thanks to Maine Sail (see below).
Any and all feedback is welcome, especially if more "canonical" information from the links cited conflict with my summary.
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Systems: OceanPlanet (Lithionics), Victron, MasterVolt, Redarc (Oz specific?)
Bare cells: Winston/Thundersky/Voltronix, CALB, GBS, A123 & Sinopoly
Best to size your cells for two parallel strings for redundancy, unless you have a separate reserve/backup bank. Don't go past three, or you may see balancing issues that affect long-term longevity, maybe four in a pinch.
Note nearly **every** vendor, also those of ancillary hardware touted as "LFP ready", gives charging voltages **way too high** for longevity.
Optimizing for longevity is just not high on their list of priorities. All their focus is on their main customers, the military and EV propulsion, where range/per-use capacity is everything and expected lifespan is short anyway. EV's high C-rate usage is **very** different from our much gentler House bank cycling. Note also that most EV people talking "lithium-ion", mean other chemistries not as safe as LFP, much shorter lifetimes, and with completely different setpoints and behaviors.
Gentler House bank*storage*use cases are .0001% of the cell manufacturer's market, so therefore no testing / different specs are developed for that use case; that has been left to the end users, and the more objective/technical vendors like*Maine*Sail.
Consider also, that the auto industry could easily have developed utilitarian cars and*parts*supply chains, so that consumers could routinely drive them for 50-100 years. For purely rational free-market economic reasons, that has never happened.
So, following those vendor charge specs is fine if you only want the cycle lifetimes they advertise. You can however get **much** longer life by "avoiding the shoulders", look at the SoC vs Voltage chart, and avoid the "shoulders" at both ends, stay in the smooth parts of the curve.
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My end-charge voltage setting for charging LFP is 3.45Vpc, which for 4S "12V" = 13.8V max. Note that is usually at an amps rate of around .3C, or 30A per 100AH. At higher rates, to shorten ICE run-times it is safe to go to 3.5Vpc / 14.0V. Also at **very** low charge rates, I back off to 3.40Vpc / 13.6V.
For daily use cycling, best and simplest is to "just stop" charging when your end-point voltage is reached. A long Absorb stage is holdover "lead thinking".
For precise benchmarking of 100% SoC, an endAmps spec of .03C (3A per 100AH) or even .05C is fine, but otherwise Absorb time only gets you another percent or two actual SoC capacity, mostly surface charge or dissipated as heat, and at charge voltages over 3.5Vpc will reduce longevity.
Note even at the "low" max charge voltage, letting the charge source continue to "push" even low currents long **past** the endAmps point is over-charging, and will reduce lifecycles.
Note that "stop charging" may simply mean isolating the LFP bank, if you want your charge source to carry ongoing loads rather than discharging your LFP bank.
But if you can't do that or just prefer to Float, then at least set the Float voltage well below your bank's resting Full voltage point, at say 13.1-13.2V. But that is a compromise, and *may* somewhat shorten life cycles.
With LFP, you don't need to ever fill up all the way, as far as the cells are concerned. In fact, it is bad for them to sit at Full for more than a few minutes. Therefore only "fill up" if consumer loads are present, ready to start discharging, ideally right away.
Charging at .5C or even higher is no problem if you want to minimize ICE runtime, as long as your wiring is that robust; vendors may spec lower rates out of legal caution. .3C or lower charge rates are better for longevity.
And of course, we're talking about gentle "partial C" House bank discharge rates, size appropriately and be careful feeding heavy loads like a winch or windlass.
Many sources claim there is a "memory effect" from keeping charge voltage and ending point exactly the same every time lower than manufacturer specs, that can apparently over time lead to apparent lower capacity. Their recommended fix is to "go higher, into the shoulder" every so often, similar to "conditioning" a FLA bank monthly. IMO you can also prevent the issue, by varying your setpoints a bit, sometimes go a point or two higher or lower, vary Absorb time a bit etc. There is no consensus just how serious this problem is.
Store at a low SoC. "Not over 50-60%" say most, to compensate for self-discharge, if not getting topped up regularly (I would at least monthly). "Lower the better" say many more recently, as long as you take **zero chances** letting self-discharge drop below 10-20% SoC, certainly not below 3Vpc. Isolated from everything including your BMS and cooler the better.
Letting the batts go "dead flat" = instant **permanent unrecoverable** damage.
Same with charging in below 32°F / 0°C freezing temps.
Persistent high temps also drastically shortens life.
Again, going above 3.5Vpc won't add much if any AH capacity, but will shorten life cycles dramatically.
Following these tips, letting the BMS do active balancing is unnecessary and potentially harmful, IMO just look for LVD / OVD and temp protection. Multiple layers of protection are advised if it is a very expensive bank, so you don't rely on any one device to keep working.
Check cell-level voltage balance say monthly to start, then quarterly, finally every six months if there are no imbalance issues, but only if that seems safe to you.
This thread is long but informative
http://www.cruisersforum.com/forums...or-those-using-them-as-house-banks-65069.html
, make sure to give both Maine Sail and Ocean Planet your close attention.
Also MS' summary notes here
https://marinehowto.com/lifepo4-batteries-on-boats/
**Everything** at that site is worth reading, very valuable.
https://marinehowto.com/support, feel free to make a donation to help with those expenses. He also has great articles in Practical Sailor.
Anyone actually setting up House banks from LFP, do please report back here!
