First thing, I really like how the cells react compared to lead acid, the charge efficiency seems a lot better, no waste in absorption.
They hold the load very well too, the voltage goes down very slowly and predictably.
I didn't try big loads yet, the biggest was the hoover, a bit above 1200W and absolutely no sign of warming, I'll try to drain more power in a few days and watch with the thermal camera, but first I need some sun to charge.
I had an issue though, I let everything plugged during the night to see how well it hold the charge (2 fridges, the inverter, the 18650 process...).
During the 5 first nights all was ok, there was remaining around 20% energy in the morning, but in the 6th night the voltage dropped dramatically, 4 packs were still at 3.30v, the next one was 3v, the next one slightly above 2v and the last one slightly bellow 2v...
That's the goal of testing I guess, so I unplugged every packs, recharged to 3 volts the lowest and then went to work thinking about what happened.
And the interesting learning that comes out of this is than the biggest voltage drop was in the pack with the less cells. Just a reminder, I decided to make 100 Ah packs by matching the number of cells, 80x 1250 cells for the full pack and 51x 1950 for the more empty. I knew this wasn't going to be perfectly accurate and now I can see clearer. Those simple math are done with the capacity mesured with a 1C discharge rate, but we now that if you discharge at a lower C rating, the capacity raises, my guess is than it raises more on a 80 cell pack than on a 51.
So I add a few cells in the packs (very easy to do BTW), re-balanced them and I'm looking forward to see how it goes.
One last thing about balancing, the first time I blanced them (at 3.8v), I noticed than they were drifting a bit while reaching full charge (4v) and same thing with low voltage (3.3v) but everytime they were around 3.8v, the balance was still perfect. Two conclusion : first, this was a clue that some packs were a bit weaker, the ones I noticed then were the ones which fell around 2v. Second thing, I think as long as you don't reach the top or the bottom of your packs, they can be slightly uneven without unbalancing.