Deondti

(Updated info further down in the post)
I create a very simple Python script to interrogate the Pace BMS as used in some popular lithium battery brands. I've also packed this as a Home Assistant add-on, but can just as well be used as either a standalone script / within a docker container.
It reports the voltage of cells, temperatures, the pack's current, voltage, SOC, SOH, and a few other metrics.
Use at own risk. 
Either a serial link to the RS232 port or via IP (using some port server over TCP) will work.
Repository: https://github.com/Tertiush/bmspace
The script serves by needs atm, so any further developments can be done by the community.

UPDATE:
I've rewritten most of this script using the official PACE RS232 Protocol definition. The script now supports multiple packs!
I've only implemented informational messages / retrieving data, no commands.
Use at own risk!
Many new fields are now retrieved such as warnings, balancing data, status indications, etc.

UPDATE
 
I have reported this to DEYE , gave them my dongle Serial and 30minutes later they updated the dongle firmware over the air, WORKING 100% now

I have a 16kw Deye @Deondti , absolutely love it, the thing is a beast. 
Agree 100% with Sidewinder, the dongle from smarthomeintegrations is the way to go. 
You can either use the one without his firmware and load firmware on using Slipx06's ESPhome code. 
Or you can use his one with his firmware on it which is a bit easier to setup, I made video's on both options some time ago.
Either way much easier than trying to go down the RS485 board method which is notoriously more difficult to get working. 
 
 

@Deondti,
Your HA is getting it's info from the dongle, you will see the same error/reading, that you see on the app. Maybe a Deye F/W upgrade?
If you don't solve this, consider dropping the Deye app, and just install this https://smarthomeintegrations.co.za/product/smartdeyedonglev4/ 
The most difficult part you've already solved....the HA part.
Just follow the SMI's github/youtube video's.
WARNING!!!!, after this, you may become addicted to stats/graphs/animations/automations etc 😃

I managed to find the settings in PbmsTools 2.5 to change the numbers of cells, It's under "System Config" and then "Cell Number Setting" You have to type in the number of cells you have and then click "Setting" in order it to save the number.
When I changed the BMS settings from 16 cells to 15 cells, the BMS no longer monitored cell 14, (was expecting it to no longer monitor cell 16) but continued monitoring cell 15 and 16. I had to move the wire from cell 15 to the cell 16 input on the BMS and the wire from cell 14 to the cell 15 input on the BMS. The cell 14 input on the BMS is now no longer connected to any cells. Now on the BMS display, it has a dash - next to cell 16 instead of 0V and the low cell fault has disappeared.
I'm not sure if there's a local supplier of Pace BMSs, I got mine on Facebook Marketplace, the seller had a 52V 100Ah battery that had a few cells fail. He kept the cells and sold me the empty box and BMS.

my comms issue was solved with this firmware, over 2 months without the error