Almost all cases of voltages showing incorrectly when the pack is not under load are a result of wiring errors (or a result of damage to the BMS unit from previous wiring errors). If one wiring error exists in a cell group, all measurements within that cell group may be incorrect.
Resolving the issue:
Step 1. Open the BMS utility, connect to the Orion BMS, and then go to the Diagnostic Trouble Code screen.
Look for “open wiring fault” or “low cell voltage fault” error codes (labeled “open cell voltage fault” in older versions of the utility). This particular error code indicates that the Orion BMS has detected a wiring problem which causes many other faults and means that the BMS is aware that cell voltage measurements are wrong. Refer to the “Wiring Fault Error Code” section under Diagnostic Trouble Codes later in this manual for steps to correct this error. If other error codes are present, address them as well using the information found in the Diagnostic Trouble Codes section of the manual. On revision E units, some wiring faults will appear as “low cell voltage fault” codes due to new protection circuitry. On revision E units, “low cell voltage faults” may indicate either a wiring problem or a dead cell. If there is a possible wiring fault, do not leave the cell voltage taps connected to the BMS unit for long periods of time as it may drain the cells.
Step 2. If cell voltages are measuring zero when they should be connected, ensure that cells are properly “populated.”
The Orion BMS is sold with measuring capabilities in multiples of 12 cells. However, most applications do not have exactly that number of cells and therefore the BMS has to be told which cells are connected to it in which order. Unpopulated cells are ignored by the BMS and show up as zero volts. The population settings can be seen and modified in the BMS utility on the Battery Profile tab under Cell Settings -> Cell Population Settings. Verify the population table is correct and that the settings have been properly uploaded to the BMS. For more information on cell population settings, please refer to the software manual.
Step 3. Ensure that at least 4 cells are wired in the cell group, totaling a minimum of 12v.
If fewer than 4 cells are wired in a “cell group”, the BMS cannot accurately measure the cell voltages, please refer to the wiring manual to correct the wiring or for more information on ensuring wiring is correct.
Step 4. If fewer than 12 cells are wired into the affected cell group, ensure that each of the unused wires in the cell group is connected to the positive terminal of the highest potential cell.
Please refer to the wiring manual for information on correct cell tap wiring.
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