Problems with BMS communication

[billvon]

I have had no luck so far trying to get the MN15 to communicate with the battery system (four EG4 server batteries with an EG4 hub.)

The MN15 is set to Pylon protocol.  Per the MN15 pinout sheet, RS485 A is on pin 1 and RS485 B is on pin 2 of the RJ45 connector.  Pin 3 is listed as GND_S which I assume is signal ground for the RS485 bus.


The EG4 is also set to Pylon protocol.  The EG4 hub has RS485 B on pin 1 and RS485 A on pin 2.  There are no grounds on the RJ45 connector on that end.

I made a crossover cable to connect pin 2 on the MN15 to pin 1 on the EG4 hub and vice versa.  I did not connect the ground.  Before making the final data connection I looked at the potential differences between the two RS485 buses (with the DC breaker on) and they were very low (<100mV.)

After making the data connection I still get D8-Communication error (Inverter-BMS) and D1-Battery absent errors.

When I look at the signal with a scope, there is no data present, and both lines are floating at about 2.5 volts.

The battery chassis is connected to the MN15 ground, and the DC power is good (53V at the MN15 battery terminals.)  The EG4 battery communication is working between the batteries and the hub, and I can see all four batteries from the EG4 hub's front panel.

Anyone have any ideas?  Is there any way to cause the MN15 to send data so I can check to see that it is making it to the EG4 hub?  Also is there a way to monitor the actual data being received by the MN15?  In the Pylontech protocol, does one side (battery or inverter) transmit spontaneously, or does there have to be a query?

Drawings and plots below.

[ClassicCrazy]

I don't have eg4 batteries or the MN15 .  I don't know what the hub is - maybe that is the issue.  Can you try just plugging your batteries to each other and then take the communication  from your master battery to the Midnite ?
That is how some other battery systems work - the master battery is all that needs to go to the inverter .
And if that doesn't work just try connecting one battery to the inverter. Of course they need to be the same type output  - can or rs485 whatever is used.

[billvon]

"Can you try just plugging your batteries to each other and then take the communication  from your master battery to the Midnite ?" - No.  The MN15 cannot accept EG4 protocol so the hub needs to be there to translate from EG4 to Pylontech (which the MN15 can understand.)

[Wizbandit]

I have had no luck so far trying to get the MN15 to communicate with the battery system (four EG4 server batteries with an EG4 hub.)

The MN15 is set to Pylon protocol.  Per the MN15 pinout sheet, RS485 A is on pin 1 and RS485 B is on pin 2 of the RJ45 connector.  Pin 3 is listed as GND_S which I assume is signal ground for the RS485 bus.


The EG4 is also set to Pylon protocol.  The EG4 hub has RS485 B on pin 1 and RS485 A on pin 2.  There are no grounds on the RJ45 connector on that end.

I made a crossover cable to connect pin 2 on the MN15 to pin 1 on the EG4 hub and vice versa.  I did not connect the ground.  Before making the final data connection I looked at the potential differences between the two RS485 buses (with the DC breaker on) and they were very low (<100mV.)

After making the data connection I still get D8-Communication error (Inverter-BMS) and D1-Battery absent errors.

When I look at the signal with a scope, there is no data present, and both lines are floating at about 2.5 volts.

The battery chassis is connected to the MN15 ground, and the DC power is good (53V at the MN15 battery terminals.)  The EG4 battery communication is working between the batteries and the hub, and I can see all four batteries from the EG4 hub's front panel.

Anyone have any ideas?  Is there any way to cause the MN15 to send data so I can check to see that it is making it to the EG4 hub?  Also is there a way to monitor the actual data being received by the MN15?  In the Pylontech protocol, does one side (battery or inverter) transmit spontaneously, or does there have to be a query?

Drawings and plots below.

I believe the MNAIO10K only does closed loop using the CANBUS.  I have never tried the RS485 so I can't comment but the CANBUS does work.