Reading Solar Charger COM via MODBUS (MAX485) Problem

[b9m]

Thanks Mark.

The charger producer certainly did something to not have it straight forward, I just wonder what it could be as they must have added something on top of the modbus approach to avoid people coming up with their own self-made solutions.

Also, their remote MT-50 monitor has changed, the older versions do not work with the newer charge controllers (Tracer A series is the older discontinued, Tracer AN is the new and current series), I have a newer charge controller.

There are two directions that I would like to further explore.

The first is related to connecting the charge controller via USB. Youtuber Adam Welch reviewed the AN version and highlighted for instance the issues with the old MT-50. He also mentions that the self-made arduion/ESP based monitoring solutions do not work anymore with the AN device, but he mentions that using the self-made USB cable works. He is using some converter like this.

....while writing this and re-watching Adam's video I was wondering why the usb cable works and the ESP/Arduino isnt, what is the difference? It is so obvious - the USB solution does not ground the charger!

I disconnected pin 7 from the microcontroller ground and get now this on the serial:

 - - - - - - - - 
PV Voltage: 
0.00
PV Current: 
0.00
Battery Voltage: 
12.47
Battery Charge Current: 
0.00
0
 - - - - - - - - 
PV Voltage: 
0.00
PV Current: 
0.00
Battery Voltage: 
12.47
Battery Charge Current: 
0.00
0

It works!
The problem is that many instructions relate to having the ground connected. The AN series is a common negative series, maybe that has something to do with the ground issue but I dont really know.

[markd833]

The fact that the error(s) go away and that you get a value back for a battery voltage that seems plausible for a 12V battery (assuming that it is a 12V battery!) suggest that you are on the right track. I'm guessing that the solar panel(s) are not connected given the first 2 PV readings. That would also increase confidence that you are on the right track and not just coincidence that a random number happened to be decoded to produce a believable voltage for the battery.

If you were still having issues, then I was going to suggest a PC type USB-RS485 adapter (like the one you linked to) and one of the PC based free Modbus tools to try an establish communications that way. 

[b9m]

Indeed, I am using a 12V battery and the device screen also showed 12.5V battery voltage. PV was not connected for this test

Originally I was planning to have an ESP-01S setup for this charger data aspect but as all my other project parts are being handled via a Mega+WiFi board that I used for testing, I also dont see any conflicts on staying with it, sensor data and charger data can be sent with just one php post setup. Very happy about the situation!

Luckily I dont currently see a need to further trouble shoot but indeed, the USB validation would have been the next step I was thinking of too.