BMS AP9921X-AP9922; alarms Low battery string or low battery voltages

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Issue:

BMS AP9921X-AP9922; alarms Low battery string or low battery voltages

Product line:

AP9922X-AP9922

Environment:

All models, all serial numbers

Cause:

BMS Master AP9921X-AP9922 or Slave Unit AP9921XS-AP9922XS won’t read one or more battery string voltages or battery voltages. If there is another master or slave unit on site (larger installations) try to swap out the unit and see is the fault follows the unit or remains in the wiring harness. Try to out rule the string wiring harness and fuses. Meter readings show good voltage thru this hardness. Also check for proper strain relief at the harness connectors where they plug into the BMS master and Slave units.

Resolution:

Repair, replace wiring harness

Replace BMS Master AP9921X-AP9922 or Slave AP9921XS (record serial numbers)

NOTE: Time saver; if you have multiple BMS master units on site, copy the config.ini file from a good unit to the replacement BMS unit. Can also use to troubleshoot; copy config from good unit to the faulty unit to see if problem is in config verses the hardware.