Stuck building 48v battery

To access individual cells in a pack, what I do is use solid copper wire that's the right size to fit into the balance plug connector. I unplug it from the BMS first. I can charge and discharge through the wires, but keep it down to less than 1A. Just unplug the pair of wires and move it over to the next hole to do the next cell.

Okay. That I have done.

I was thinking i needed to test the cell while under load to see which is failing.

If you can arrange a load for the whole pack and measure individual cell voltages while the load is applied, you can look for low cells. That's one approach. If you can charge/discharge each cell individually, that works too.

In my experience, if you have one or two bad cells, it's usually pretty obvious from the individual cell voltage measurements.

Individual cell voltages means voltage for the block (3p)?

I have done both.

I think I just need to replace 2-3 blocks out of 13 in order for everything to work well. Not a good prognosis right now.

Mario