I'm torn. Previous posts suggest to avoid going below 3.0v. I'll try a few more cycles and hopefully it improves.
Ok, After contacting bigbattery, they sent me 2 replacements. The first replacement had the same issue where cell 2 was dipping faster than the rest of the pack. The 2nd replacement had the same issue as my first battery where cell 7 was dipping.
I refuse to give up on this battery so I did more reading. As previously posted by other users, these battery chemistry has a steep slope once you go below ~3V and there's a flat region when cells are at nominal voltage. Same steep slope at the other end when charging. My initial thought is to bottom balance. My theory is when the battery has a decent charge (3.2V) then they are all in the flat region. But where in the flat region you are, you don't know. In my case cell 7 had a 3.23V reading but it was still closer to the roll off than the rest of the pack. And since I'm not charging this 100%, cell 7 doesn't move away from this hill.
Bottom balancing may have worked because I would force all cells to all be in the same spot where it's close to the hill. So when I charge the entire pack, they all move away from this knee, and when the battery is discharging, they all reach the knee around the same time.
But this would mean I would have to discharge 7 cells. So, I went a different way. I bought a power supply and connected it to cell 7 and charged just this cell by itself so I know it's farther away from the knee than it used to be.
Tonight is the first time I'm discharging it so we'll see what happens tomorrow and where they all stand.
This is how the battery was when I first got it.
This is after giving cell 7 a boost. I've never seen all cells this close ever before.
