This is a heads up for Chargery as they are redesigning their BMS. Chargery has a red ribbon cable which attaches to each of the cells to measure cell voltage. There's a problem with this mechanism as power is drawn from the ground voltage sense cable and the last sense cable connection. There's a voltage drop in these two cables leading to incorrect cell measurements for the first and last cell.
I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.
Fluke vs. Chargery comparison:
Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V
The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.
Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.
I'm using a Fluke 87 III meter to measure cell voltage directly at the cells. The meter has 0.05% + 1 digit accuracy. It is calibrated each year.
Fluke vs. Chargery comparison:
Cell 1: 3.382V ... 3.361V
Cell 2: 3.380V ... 3.381V
Cell 3: 3.381V ... 3.380V
Cell 4: 3.381V ... 3.370V
The first cell measures 21 mV low and the last cell measures 11 mV low. This can become a problem when balancing.
Chargery needs to add separate power cables to the battery to eliminate this measurement error. Power is drawn to operate the BMS and relays, etc.