I haven't done a ton of so if you have any ideas/improvements I always love to learn and improve.

Downloads of the datasheets for the inverter and databox as well as the software used to control it can be found here.

Software

When plugging in to the computer the data box shows up as a "Prolific USB-to-Serail Comm Port" with a baud rate of 9600.

I have tried various programs but haven't found something to listen to the serial communication between the data box and the computer without blocking its own program NETMS to still talk to it.

The next step I will try is to make a cable with the data lines exposed so I can use a logic analyzer to listen in.
Or maybe someone else knows a better software?

Hardware

The hardware is quite simple and only consists of a single PCB with a pic16f1947 microcontroller and a LC12S off the shelf 2.4Ghz wireless module. The external antenna is only necessary with the case on or for greater distances.

Translated Datasheet LC12S

Some more useful links about the LC12S module:

https://www.iot-rf.com/2.4g-uart-wireless-module-bk2461.html
https://forum.arduino.cc/t/lc12s-explained/695700/3
https://www.satistronics.com/shop/product/180300-lc12s-uart-wireless-serial-transparent-transmition-128-channel-module-9312
http://arduinolab.pw/index.php/2016/11/13/radiomoduli-na-24ggc-c-uart-interfejsom-lc12s/
http://user.cavenet.com/jgurley/lc12s/
https://www.pcbway.com/project/shareproject/LC12S_wireless_transceiver_module.html

I have already tied into the communication between microcontroller and wireless module and have successfully decoded the signal transmitted by the databox in order to get a response from a specific inverter. The inverter is selected by an id written on its backside. This is also the id entered in the software NETMS to add a new inverter.

These are the hex values send whenever the data box connects to the inverter or rather requests a response:

 BC 3F EC 7B FF FF C7 FF BE B9 FF FF FF FF A6        //Connect 38004146
 BC 3F EC 7B FF FF ED CB A9 87 FF FF FF FF 51        //Connect 12345678
 BC 3F EC 7B FF FF EE EE EE EE FF FF FF FF 21         //Connect 11111111
 BC 3F EC 7B FF FF DD DD DD DD FF FF FF FF DD   //Connect 22222222

According to this the first 6 numbers are always the same then followed by the inverter id then followed by 4 * FF and then another number who's purpose I'm still not quite sure of.

The response looks like this: 

 BC 3F EC 7B FF FF C7 FF BE B9 FF FF FF FF A6 //Connect 38004146
 5E 00 76 CF FF 00 EC 7D 73 00 5F 6E 5D 00 BF AF FV 00 5C A9 FE 00 7C B3 27 D1 00 //response 38004146

 BC 3F EC 7B FF FF C7 FF BE B9 FF FF FF FF A6 //Connect 38004146
 43 C0 13 84 00 00 38 00 41 46 41 23 51 00 0E 0D 60 00 44 5A 4B 00 08 00 25 6C 17 //response 38004146

Because there are many different parameters send back from the inverter I haven't quite figured out what each number means but I'm gonna run a few more tests and try to find some patterns.