First, do you have the pinout of each RS485 port.
The EG4 Lifepower4 batteries for example use pins 1&2 as an RS485 bus as well as pins 7&8 as a second RS485 bus in the same RJ45 jack.
I purchased a RS485 to USB Converter:
RS485-USB-Converter
Using a spare cat5 cable, just cut of the RJ45 connector on one end, remove about 3 inches of the outer insulation then you can connect the correct pair of wires to the RS485 to USB Converter and plug the RJ45 connector on the other end to the correct port on the battery.
Look at the RJ45 connector on the cable (With my tired old eye I use a magnifying glass) and determine the order or the wires.
With the RJ45 connector locking tab facing away from you and the bare pins facing you can determine the color of the wire to each pin. pin 1 will be on your left and pin 8 will be on the right.
T-568B RJ45 pinout
Pin Color
1 orange/white
2 orange
3 green/white
4 blue
5 blue/white
6 green
7 brown/white
8 brown
For exampe, in my case if I want to communicate to my batteries on pins 1&2, I connect the orange/white wire to the B- on the converter and the orange wire to the A+ on the converter, If I want to communicate to my batteries on pins 7&8 I connect the brown to the B- on the converter and the brown/white wire to the A+ on the converter
For the EG4 pins 1&2 are generally used for end user communications such as the User software or Solar Assistant and pins 7&8 are used when the battery is placed in Host/Master mode by settings its address to 0. The BMS in Host/master mode will then poll the other batteries in thwe stack on pin 7&8. The EG4 Communication hub als acts as a Host/Master BMS and pols all batteries on pin 7&8.
Hopefully you will be able to determine which pin combination works for you. With an RS485 to USB Converter you can try any number of combinations without the need to purchase cables only to find they do not work.