This video documents the presenter's experience with a DIY solar power setup, beginning with the installation of inexpensive 400W solar panels using custom-made mounts. Initial efforts to utilize a BlueETTI power bank for EV charging encountered difficulties with its automation and unreliable state-of-charge reporting, even after successfully reverse-engineering its RS485 communication protocol for custom control. Consequently, the presenter transitioned to a Solex 2.5kW grid-tied solar inverter, configured for zero export. The core of the video is a detailed teardown of this Solex inverter, primarily motivated by the desire to modify its LCD backlight to remain permanently on. The teardown reveals the inverter's robust mechanical design, internal architecture including a boost converter stage, an H-bridge with IGBTs for AC generation, extensive EMI filtering, a Texas Instruments DSP for control, a dedicated arc fault detection module, and an ESP32-based Wi-Fi/LAN communication dongle. The video successfully concludes with a simple modification to the user interface board to achieve a constantly illuminated LCD.
Solar Power Journey: From BlueETTI Challenges to Solex Inverter Teardown and Backlight Modification
0:00:02 Solar Panel Installation & Initial Setup: The presenter installed seven 400W solar panels, costing £60 each, using DIY aluminum channel mounts on a workshop roof and connected them to a BlueETTI power bank.
0:00:57 BlueETTI for EV Charging & Control Challenges: The initial plan was to use the BlueETTI to charge an EV. However, its internal software lacked the desired automation (turning on AC output when the battery is full). The presenter reverse-engineered the BlueETTI's RS485 protocol to gain control via a PC.
0:01:49 BlueETTI State of Charge Issues: The BlueETTI's state of charge reporting proved unreliable, showing sudden 20% jumps and inconsistencies with battery voltage, making precise control difficult and leading to power wastage.
0:02:17 Transition to Solex Inverter: Due to the BlueETTI's limitations, a Solex 2.5kW grid-tied solar inverter was acquired. It's configured to not export power to the grid, thus avoiding complex paperwork, and uses a current transformer on the incoming mains to regulate its output.
0:02:44 Solex Inverter LCD Backlight Annoyance: A minor annoyance with the Solex inverter is its LCD backlight automatically turning off, with no user setting to keep it permanently on, prompting the decision to modify it.
0:03:01 Solex Connectivity & Dongle: The inverter includes a wireless and wired LAN interface dongle. The presenter notes a design flaw where the QR code for app connection is poorly placed.
0:03:25 Solex Inverter Teardown - External Features: The inverter is a heavy, robust unit with a large cast heatsink. It features a GORE-TEX-like vent for pressure equalization in the sealed enclosure, crucial for outdoor or semi-outdoor installations to prevent moisture ingress.
0:05:40 Solex Inverter Teardown - Internal Overview: The front cover is also cast metal. Internally, the main PCB is conformal coated. The user interface board uses spring-loaded contacts for its touch buttons. An arc detection module is present, likely for safety and regional compliance.
0:07:29 Arc Detection Module: A small sub-board with a current transformer around one of the solar inputs is identified as an arc detection unit, possibly a bought-in module, crucial for detecting dangerous DC arcs from the solar panels.
0:10:00 Main Power Board Architecture: The main board features significant filtering, large high-voltage capacitors, and semiconductor devices (IGBTs) for power conversion. The architecture involves a boost converter to raise panel DC voltage to around 500V, followed by an H-bridge to generate the AC sine wave.
0:12:53 EMI Filtering and Design Details: Extensive EMI filtering is evident, including a small sub-board with capacitors directly at the solar input connectors to mitigate RF noise from the panels acting as antennas.
0:13:35 Rear Components and Power Path: Behind the main PCB are large inductors: a 750µH boost inductor and two 1.1mH inductors forming a low-pass filter with a 3.3µF capacitor for the AC output. Relays are used, likely in series for redundancy and safety. A Texas Instruments DSP controls the inverter operations.
0:14:39 IGBT Configuration and Unidentified Components: The power stage uses IGBTs for the boost converter and H-bridge. An additional pair of transistors across the H-bridge output puzzles the presenter, who requests insights from viewers.
0:15:41 Isolated Interfaces: The external interfaces (RS485, current transformer for export limiting) and the user interface (which provides USB for the LAN/Wi-Fi dongle) are on an isolated section of the PCB.
0:16:44 LAN/Wi-Fi Dongle Internals: The communication dongle, connected via USB, houses an ESP32 module and a Wiznet W5500 chip for Ethernet connectivity, utilizing a simple SPI interface.
0:17:20 LCD Backlight Modification: The primary goal is achieved by identifying the backlight power pins on the user interface board's LCD. A simple wire link is soldered to connect the backlight's negative pin directly to ground, bypassing the control transistor and keeping the backlight permanently on.