Gifted Horse Ver. 2.0

[CapnGil]

Hello All, Cell Dummy here to impose another question to the group on how to best manage or to utilize the cells “I Have". Ver 1.0 of Gifted Horse was about balancing the 8S5P bank of batteries that were gifted to me. Quick summary, this bank is the house bank aboard my sailboat and as they were, they were more than enough to manage my loads and usage. Ver 1.0 was about balancing to which I bought one but ended up with two EBC-A40L (aliexpress scammers) capacity testers. Being that I am 40% complete with my capacity testing I can now say that these 180Ah cells are averaging 145Ah's each, so I have old very used cells.... Ouch. Before I present my question, let me say that as a 59 year old disabled stroke survivor trying to live on SSI Disability I have little funds to spend on upgrades so please limit the statements about buying this or that, but I do thank you in turn for whatever advice offered.

Question:
After capacity testing and matching my new to me old cells. What setting should I set on my Daly 8S 200A BMS's? Previously I had the Ah set to 180AH, which is as you and I now see is incorrect. I also had my charge rate set to 3.4v and discharge to 3.2v with a 28v charge supply from Grow Watt 3K Hybrid Solar Controller being supplied by six 285w Solar Panels. With these settings I rarely was concerned of draining my bank as they were, also South Florida sunshine is plentiful. Once again, I don't run much full time other than the three 24v refrigeration compressors.

Kinda 2nd question. Being that my 180Ah cells are now true 140Ah, what can I expect of them as I move forward? Will these cells provide another 500 cycles, more than I need? Note since I've had them, about two years, and with the usage expected to remain the same. The Daly BMS Ap has shown an average of 12 cycle each, with high cycle being 22 and lowest being 8. The only difference moving forward will be my rude awakening knowledge of what cells I have, better or more suitable (What suggestion are offered here) 140Ah BMS settings, cell matching all banks, 80% usage (more like 65%) remains the same, and as always plenty of solar as compared to usage loads?

Once again, I thank you all for your input
Be well
Gil

 

[sunshine_eggo]

One BMS or 5 BMS?

8S5P implies 8S first, 5P second - 5 parallel 8S batteries.

5P8S implies 8 groups of 5P cells in parallel, i.e., one battery, one BMS.

The lowest "cell" capacity dictates your total battery capacity.

I would expect 500 cycles to be attainable if LFP. End of life of LFP is about 70% rated. that's 126Ah on 180Ah rated cells. You're at about 80%.

Would expect at least 600 cycles. more if you treat the battery more conservatively. Absorption @ 3.45V for up to 2 hours and float at 3.375V.

Recommend you input the cell capacities into a spreadsheet and sort by capacity.

If 5P8S:
When building your 5P "cells", select cells alternating the ends of the list, e.g.,
Cell 1 is max cap.
Cell 40 is min cap.
First 5p cell would be: 1, 40, 2, 39, 3
Second 5P cell would be: 38, 4, 37, 5, 36
etc.

Then sum the capacities of each 5P cell and your battery capacity will be the "cell" with the lowest capacity.

If 8S5P (5 parallel 8S batteries)
Use the same list and pick consecutive cells as they will be the closest to each other, e.g.,
Battery 1 is 1-8
Battery 2 is 9-16
etc.

The lowest cell in EACH 8s battery is the capacity of that 8S battery, i.e., cell 8 in #1, Cel 16 in #2, etc. Your total capacity would be the sum of cells 8, 16, 24, 32 and 40.

 

[Supervstech]

With a single 200A bms, you are limited to about 5000 Watts...

With five 200A bms, one on each string of 8 cells in series, you could pull 25,000 watts...
And the cells would balance much quicker.