This issue can be caused by incorrect cell population settings, wiring errors,, not enough cells in a cell group (wiring error), cell voltages too low, a BMS utility problem, incorrect size of BMS or internal damage to the BMS.
Resolving the issue:
Step 1. Exit the BMS utility and open it again.
Older versions of the BMS utility had a software glitch where some cell voltages were not displayed correctly in the utility, although the BMS was correctly measuring the cells. If the problem disappears, please ensure that you have the most up to date version of the utility.
Step 2. Check the cell population table settings.
Using the BMS utility, load the current profile into the workspace (usually by downloading settings from the BMS.) Click on the “Cell Settings” tab and click the “Cell Population Settings” button. Ensure that the correct number of cells in the correct locations are checked as “Populated”. The BMS relies on this table to know which cells are supposed to be present and will ignore cells which are not checked as “populated.”
Step 3. Insure that each cell group has a minimum of 4 cells populated.
Step 4. Ensure that the cell voltage taps connectors are plugged into the correct connector on the BMS.
Newer revisions of the BMS have a legend of the connectors on the bottom of the BMS. Also, ensure that the BMS you have is internally “populated” on the connector you are connecting to (i.e. a 24 cell BMS only has the first 2 cell groups populated and cannot measure voltages on the 3rd cell group or on any other connector.)
Step 5. Measure the voltage of the “missing cells” using a multimeter.
Ensure that the sum of voltage of all cells in the cell group is at least 10 volts. The BMS will not report cell voltages if the sum voltage in a cell group is less than 10 volts.
Step 6. Inspect the wiring and ensure that voltage is present on the cell taps and that the wiring is correct.
Use the cell tap validation tool (which can be rented or purchased) to verify correct wiring. If cells are wired backwards, the BMS may see negative voltages which will show up at 0V (and may cause damage to the BMS.)
Step 7. If certain cell voltages are still not able to be read, contact Ewert Energy to evaluate the unit for possible internal damage.
Copyright (C) 2015 Ewert Energy Systems