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MS-7K-U Batteries are Not Detected

Issue

Some or all the batteries cannot be detected during the commissioning process. On rarer occasions, this can happen after commissioning as well.

Solution

  1. Confirm that the maximum distance between the gateway and the first battery does not exceed 50 metres.
  2. Doublecheck the CAN communication cabling is wired correctly and properly inserted in the terminals.
    1. Confirm and record the cable colours used for CAN H, CAN L, GND, and DRAIN.
    2. Confirm the DRAIN cable is used between batteries.
    3. Confirm the CAN H, CAN L, and GND cables are correctly connected at the Combiner Box. Refer to the associated labels.
    4. Confirm the last battery has the provided 120 Ohm resistor between CAN H and CAN L at C2.

      battery_can2
  3. Add another 120 Ohm resistor in parallel at C2 of the last battery.
    1. For 6+ batteries, you may need a total of 3x 120 Ohm resistors.

      battery_2 resistor

  4. Verify the CAN bus resistance:
    1. Power off the system.
    2. Disconnect the CAN cable at the Combiner Box.
    3. Measure the resistance of the CAN cable between CAN H and CAN L.
      1. For 2 resistors, you should measure 60 Ohms.
      2. For 3 resistors, you should measure 40 Ohms.
      3. If the actual measurements are not expected, double check the wiring, connections, and resistor.
    4. Power on the system and check if all the batteries can now be detected.

battery_resistor 60ohmbattery_resistor 40ohm

If the above does not resolve the issue, further investigations are required. To provide context, termination on the CAN bus is required at both ends of the daisy chain, one at C2 of the last battery and the other at the gateway. Typically, there is a 120 Ohm resistor at both ends resulting in an overall resistance of 60 Ohms.

For a typical scenario where there is only 1 resistor at C2 of the last battery:

  1. Power off the system.
  2. With everything connected, measure the resistance between CAN H and CAN L at the gateway. This should read ~60 Ohms.

    battery_resistor 60ohm_gateway
  3. Disconnect the CAN cable at the Combiner Box.
  4. Measure the resistance of the CAN cable between CAN H and CAN L. This should ready 120 Ohms.
  5. Reconnect the CAN cable at the Combiner Box.
  6. Remove the terminal block from C2 of the last battery.
  7. Measure the resistance of the C2 CAN terminal between CAN H and CAN L. This should read 120 Ohms.
    battery_resistor 60ohm_c2

 

If the actual measurements are not expected, double check the wiring, connections, and resistors.

Resistances measured will differ depending on the number of resistances used.

 

Information in this article was current at the time of publication or last update. Product specifications, software, firmware and procedures may change. Please refer to the latest ATMOCE documentation before proceeding.