Different voltages between cell case and poles for each cell

[Felix_123]

Hi all,

I have just received my EVE LF230 cells. They all look fine, IR is at about 0.21 mOhms and they are all at 3.30V, so far so good.
I've read somewhere that the aluminium cell housing is connected to one of the poles, but I forgot which one, so I decided to quickly figure it out with my multimeter.

The black plastic top cover has holes in it where the QR code is and where the "+" and "-" are etched in to indicate the polarity of the poles, so its easy to measure voltage diffence to one of the poles.

Here is where it gets confusing:
For the first cell the case is cleary connected to the positive pole: 0V difference and correspondingly 3.30V difference to the negative pole.
For the others however, the voltage between the case and the negative pole is 2.4V, 2.5V and 2.6V and the voltage to the positive pole is the respective remainder to the full cell voltage of 3.30V.

I am very confused, can somebody explain this?
(In case it makes any difference: I'm currently top balancing the cells, so I've measured this while they are all connected in parallel (with insulation sheets between them) and being charged with ~6A)

 

[sunshine_eggo]

Hi all,

I have just received my EVE LF230 cells. They all look fine, IR is at about 0.21 mOhms and they are all at 3.30V, so far so good.
I've read somewhere that the aluminium cell housing is connected to one of the poles, but I forgot which one, so I decided to quickly figure it out with my multimeter.

The black plastic top cover has holes in it where the QR code is and where the "+" and "-" are etched in to indicate the polarity of the poles, so its easy to measure voltage diffence to one of the poles.

Here is where it gets confusing:
For the first cell the case is cleary connected to the positive pole: 0V difference and correspondingly 3.30V difference to the negative pole.
For the others however, the voltage between the case and the negative pole is 2.4V, 2.5V and 2.6V and the voltage to the positive pole is the respective remainder to the full cell voltage of 3.30V.

I am very confused, can somebody explain this?
(In case it makes any difference: I'm currently top balancing the cells, so I've measured this while they are all connected in parallel (with insulation sheets between them) and being charged with ~6A)

In my experience (approximate):

(-) to case: 2.6V
(+) to case: 0.7V

I would not trust the measurements of all cells in parallel. I would withhold judgment on any anomalies until the cells are separated or in series.

 

[venquessa]

Are you measuring with a HiZ meter ... do you have one with a LoZ mode?