help with Em3v battery

Hello, I have a 1 year old 30 amphora, 52 volt triangular frame battery from EM3v.
I have been having a hard time with it cutting out on me and not being able to charge.
I have replaced the Bms, first with a smart bms form em3v, and also 2 other types to no avail.
I have checked the voltages at the ins on the cable going to the BMS.
Here are the values after charging.
4.0
8.1
12.1
16.1
20.1
23.7
27.4
31.1
35.2
39.2
43.2
47.2
51.3
55.3
after bypassing the bms and running the bike at a low speed on a stand to drain the battery some, here are the voltages.
3.7
7.3
11.1
14.8
18.4
21.5
24.9
28.3
32.0
35.7
39.3
43.0
46.7
50.4
Please help, I am also wondering where to buy a non- smart, simple bms that is reliable, and or a charger that will balance the cells.
Thank you so much for your advice. Johnny

You might already know this, but you've got a rather extreme problem with cell balance - more than any reasonable BMS can fix overnight or within any reasonable time period.

Based on the numbers you've provided, your cell voltages are as follows.

After charging:
1. 4.0v
2. 4.1v
3. 4.0v
4. 4.0v
5. 4.0v
6. 3.6v
7. 3.7v
8. 3.7v
9. 4.1v
10. 4.0v
11. 4.0v
12. 4.0v
13. 4.1v
14. 4.0v

After your battery draining:
1. 3.7v
2. 3.6v
3. 3.8v
4. 3.7v
5. 3.6v
6. 3.1v
7. 3.4v
8. 3.4v
9. 3.7v
10. 3.7v
11. 3.6v
12. 3.7v
13. 3.7v
14. 3.7v

Difference (Charged - Discharged) in voltage:

1. 0.3v
2. 0.5v
3. 0.2v
4. 0.3v
5. 0.4v
6. 0.5v
7. 0.3v
8. 0.4v
9. 0.4v
10. 0.3v
11. 0.4v
12. 0.3v
13. 0.4v
14. 0.3v

Although cell groups 6, 7, and 8 are each problematic, group 6 appears to be the leading reason your pack cuts off prematurely. It's the lowest cell group and it's one of the weaker cell groups, losing voltage faster than most of the others during discharge. Especially considering that you've already tried several BMSes, I suspect that you need to look away from the BMS, and toward the cells, to find and to fix your problem.

You can charge individual p-strings of cells through the balance wires at low current. If you can get them to within 0.2 volts of each other the bms should be able to balance properly when charging to full. The Em3ev smartbms will balance below full charge, but I dont know the exact threshold. After the pack is nicely balanced you can do a controlled discharge to check for capacity. You can keep track of cell-voltages live if you use the bluetooth bms app from Em3ev. If everything is nice and even you are good to go, else some surgery might be neccessary to fix the pack.

The root problem is the cells in those problematic groups. To fix this you would need to replace them with new cells.

Once taht is done, then eventually the balance problem will become opposite, though that will take time and multiple cycles, where the new cells will stay charged fine, but the old ones will become imbalanced instead, and you'll have to keep replacing groups of cells.