LiFePO4 system design considerations and sources for off-grid battery bank replacing lead acid
I need to replace my lead-acid battery bank prematurely and I am going LiFePO4. I need between 600 and 800 kwh and I've described below what I am leaning toward. Based on 6 years with 470 Ah lead acid bank, my pulls are typically less than 40A and I have only very rarely seen 50A for a short time. I have a Tristar 60 MPPT controller. Before my wife and I destroyed the batteries recently, we rarely went under 80% unless there were several days of clouds or snow. We live at altitude in the sunny SW.
96 Fortune 100Ah batteries https://www.electriccarpartscompany.com/Fortune-100Ah-Aluminum-Encased-Battery hooked in groups of 6 parallel, then series to get nominal 48V 600Ah
BMS leaning toward Orion Jr 2 https://www.electriccarpartscompany.com/Orion-Jr-2-BMS
which also requires 16 LED https://www.electriccarpartscompany.com/3V-1S-Lithium-Lighted-Battery-Balancers
I am curious about what you think about this overall system, is there a better way? I opted away from the cheaper BMS because I am worried about failure and Orion seems to have a good rep.
I am also curious about anybody's experience with Electric Car Parts Co?
Also, there are Powerwall options from Greensun and Meritech where you get a complete system of batteries and BMS that would be cheaper for more power but I am leery about an overseas transaction and the lack of support I'd be likely to receive. Does anybody here use one of the pre-built Chinese "Powerwalls"? I could get 800Ah powerwall shipped for under $11,000.
Among the things I am worried about is will shallow cycling (we do have occasional deep cycle needs but less than 20 times/year) will shorten the life of lithium batteries if they are fully charged between cycles?
Should we charge them to the max rated voltage of 3.65 cells each cycle or would it be better to only go up to 90%?
Will the BMS work if it is hooked only to each parallel group, i.e. each group of 6 batteries in parallel will have one balancer? The only drawback I can come up with for doing this is that if one cell is failing, the other cells in that parallel group will be stressed until I notice that the group is lower than the rest and replace the cell.
What else should I be losing sleep over?
Any thoughts are welcome. I already know that I am ignorant and on a nearly vertical learning curve about lithium set up.
12 * 300 W (10 fixed rooftop, 2 movable pole mount), Morningstar Tristar MPPT 60, Magnum 4448 PAE, 16 Crown CR-235 6V in two parallel sets of 8 (470 Ah)
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