Quite a bit of misunderstanding above. In no particular order:
1. Mastervolt Lithium batteries are radically overpriced. I paid under $11,000 for 120 CALB CAM72 cells with 27KWh. These are high-end, very light cells.
2. LiFePO4 (excellent for boats) and LiCoO2 (dangerous fire hazard and complex to charge) are both Lithium-ion, so the term Lithium-ion does not specify the battery type.
3. Leaving LiFePO4 cells at a state of charge below 20% for long periods will reduce the lifespan of the cells from several thousand cycles to just a few thousand cycles, where lifespan is defined as capacity reduced to 80% of spec. Contrast that to lead-acid where lifespan is a few hundred cycles (I've never seen 500 from any variant of lead-acid, gel, AGM, etc.) and which are just about completely unusable when they reach that.
4. The LiFePO4 cells that most of us buy do not have any kind of chip inside. Many people are buying
BMSes that are meant for high C charging and discharging (up to 10C and higher) and which are, in my opinion, a complete waste of money
for low C charging and discharging such as we use on boats (typically under 0.5C and often under 0.2C). In the vastly more stressful (for batteries) world of electric cars, people have driven dozens of thousands of miles using LiFePO4 with no BMS and zero measurable drift in cell voltages. Don't overcharge or over-discharge and LiFePO4 cells don't diverge. In my opinion, a BMS on a marine house bank is snake oil
5. I don't ever plan to discharge below 20% SoC (state of charge) but I know that I can safely discharge to 1% if necessary, at the expense of a very small reduction in lifespan. It's only that last 1% where the voltage starts dropping fast that significantly reduces lifespan. Don't discharge below 2.8V or 2.9V per cell.
6. Charging. Except for initially balancing the cells, which is critically important, never charge at voltages above 3.45V per cell (13.8V for a nominal 12V system). I never charge above 3.40V per cell (13.6V for a nominal 12V system). Charging a nominal 12V LiFePO4 battery at 14.3V will reduce its lifespan for no real benefit. 13.6V will charge the batteries to about 99% as full as 14.3V and 13.8V will charge them to about 99.9% of what 14.3V will. Why cut the lifespan of batteries in half for a few extra watt-seconds? With an alternator
or genset, I would be tempted to use 3.45V per cell to slightly reduce charging time and diesel consumption
, but I would never go over 3.40V per cell with solar
, or a shore charger
. 3.40V is gentle enough that it can remain connected after the cells are fully charged.
7. Initial Balancing. Use 3.65V (with the cells connected in parallel) for initial balancing. Hold the voltage there for about two hours, then disconnect the charger and leave them connected in parallel for a few weeks before connecting them in series for use.