Voltage sag reading between lipo packs serial connection

[rg12]

I have done this setup many times of connecting 3pcs 7s lipo packs in seriel but few times with a bms.
The problem is that the separate voltage readings of each cell had 2 inaccurate readings for the cells that connect together between packs.

Now I don't remember if I have done option 1 or 2 (I think it was 2) that produced a wrong reading for the last cell of pack #1 and last cell of pack #2.
The reading under 0 load was perfect but under load those two cells showed 0.30V sag which wasn't happening in reality but only because of the voltage drop across the wires that connect the packs that are paralleled with the sense wires of the same cells.

Situation #3 in this diagram have cut the voltage drop reading by half to 0.15V (all other cells are sagging about 0.03V).

My question is, how can I avoid this voltage drop reading?

 

[calab]

What kind of load was it?

Might be that the electron flow takes a longer path for the groups furthest away from the main connector putting more stress on the furthest away groupings. Try the best you can to make the electron flow as even as possible. Look at the picture below.

Other reasons could be:
Best to have matching gauge wire, different gauge wires have different resistances.
Look at your connection method, spot welds or solder.
Could be a reading error on your part, not enough pressure on the dmm probe, some glue on the probe point, cheap dmm, low 9v battery in the dmm.
Just a weak cell

I have done this setup many times of connecting 3pcs 7s lipo packs in seriel but few times with a bms.
The problem is that the separate voltage readings of each cell had 2 inaccurate readings for the cells that connect together between packs.

Easier to understand with a diagram then write out an explanation.

 

[DogDipstick]

Gold. I use gold.

Gold Cannons. Along with an expensive crimper.