Hi,
I noticed my BMS16T cell measurements are not accurate as some of the cells report higher or lower voltage than my DMM. I have a 2.5V reference standard and have adjusted the DMM numbers to correct for its 0.00271V low readings:
I included cells 3 and 4 comparisons to show that the BMS and DMM do measure the same voltage in some cases. Comparing cell 9 to cell 16, there is a difference of 58 mV. That means when I try to charge the bank to 58.4V, cell 16 hits HVD while cell 9 is still around 3.592V. I guess that's not so much of a problem given cell 9 is still above 99% capacity. However, I plan to charge the bank to 56V (3.5V/cell) normally, so cell 9 will only reach 3.442V. Since this is in the flat part of the curve, the stored energy in that cell could be much lower than cell 16. So, this is a problem, right?
Just to anticipate the question, I thought maybe the connector terminations were defective so I replaced some of the ring terminals with the highest discrepancies with no change in the results.
I noticed my BMS16T cell measurements are not accurate as some of the cells report higher or lower voltage than my DMM. I have a 2.5V reference standard and have adjusted the DMM numbers to correct for its 0.00271V low readings:
Cell # | BMS Reading | DMM Reading | BMS vs DMM | |
3 | 3.325 | 3.325 | 0.000 | |
4 | 3.329 | 3.329 | 0.000 | |
9 | 3.300 | 3.322 | -0.022 | |
10 | 3.359 | 3.327 | 0.032 | |
16 | 3.360 | 3.324 | 0.036 |
I included cells 3 and 4 comparisons to show that the BMS and DMM do measure the same voltage in some cases. Comparing cell 9 to cell 16, there is a difference of 58 mV. That means when I try to charge the bank to 58.4V, cell 16 hits HVD while cell 9 is still around 3.592V. I guess that's not so much of a problem given cell 9 is still above 99% capacity. However, I plan to charge the bank to 56V (3.5V/cell) normally, so cell 9 will only reach 3.442V. Since this is in the flat part of the curve, the stored energy in that cell could be much lower than cell 16. So, this is a problem, right?
Just to anticipate the question, I thought maybe the connector terminations were defective so I replaced some of the ring terminals with the highest discrepancies with no change in the results.