Microcontroller projects

Solar Master: Monitor your panels

* coming soon (this year ;))*

last updated: 2024-03-11


After 20 years of use my different solar panels have to be rewired to fit my new battery system. At the same time, they are cleaned and it would be interesting to get the U/I curve of the panels to compare them and detect faulty or weak panels.

I needed a load to change the current and measure the voltage. And after a short search I found an electronic 500W load on Aliexpress with a resistance up to 1000 Ω (type14 0-100 V 0-20 A):


The challenge was to understand the communication with the load, ass all documentation was in Chinese (and my Chinese isn't so good ;)).


The load

The load is from SOUSIM:


The only information that I could find was from the this EEVblog forum: https://www.eevblog.com/forum/testgear/chinese-electronic-load-500w-module-sousim-500w/.

For the load we need a DC power source (12 V, 1 A) and the communication is done via Modbus RTU (Terminal with A+ and B-). This is a differential signal and needs no ground.


The housing is drawn in FreeCAD. The stl files are on github.