Not really, the old cells have lost less than 4% from nominal as I'm only using (and testing) 70% of their gross capacity from 90% SOC down to 20% SOC. Read back on post, https://camelot-forum.co.uk/phpBB3/view ... 120#p59144Stinsy wrote: ↑Mon Apr 21, 2025 9:21 pm Let’s compare what you thought prior to this test:
With what you’ve measured:Battery Bank 1 is 24.37 kWh of LMC but is a decade old.
Battery Bank 2 is 24.37 kWh of LMC but is a decade old.
Battery Bank 3 is 28.67 kWh of LFP and is only a month old.
Battery Bank 4 is 32.26 kWh of LFP and is only a couple of days old.
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Total Gross Capacity 109.67 kWh
So the old cells are showing their age, but assuming their efficiency is still good, then seeing as they were “scrap” when you bought them they’re doing a great job. What is your plan to figure out if a dud cell is pulling the pack down?Test 2 - Battery Bank 1 + 2 (LMC cells) was 32.4 kWh
Test 3 - Battery Bank 3 (LFP cells) was 28.9 kWh
Test 4 - Battery Bank 4 (LFP cells) was 32.6 kWh
Total of individual tests adds up to 93.9 kWh
And the new cells are in-fact better than you thought!
I could have tested them on their full voltage range, but it would be pointless as I am testing my usable operational capacity. Having the 14 cell LMC's in parallel with the 16 cell LFP there has to be a compromise of voltage settings and the LMC's have to take the hit. LMC are safer using a narrower voltage range and inherently have less cycle life than LFP especially if you use the full capacity of them. LFP on the other hand have a ridiculously high cycle life and safer even if pushed hard.
I'm not particularly surprised on how good the new cells are otherwise I would not have bought them, I do trust Fogstar as a supplier, they have an office out in China so they do check where they are buying their stock from. But I do take comfort in that my results tally up with the printed capacity stickers on the cells which are higher than nominal.
What I am surprised about is I cannot find any obvious or even less obvious faults with the "Grade B" cells at all.
From what I understand they are grade B if,
- They are more than 6 months old and still on the shelf. They are all less than 6 months old, at least according to their stickers.
- Their new capacity is less than nominal. Their capacity marked and measured by myself tally and are higher than nominal.
- They have any bulging, minor dents, or other physical defect. I cannot find even the slightest blemish on any of them.
- Their internal resistance is higher than spec. I have bought an internal resistance meter and they are within spec.
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