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CN3791 - Hardware details

Pinout​

MPPT Charger Board pinout image

Click here for a high resolution image of the pinout.

Pin Details​

Pin MarkingDescription
IN+Solar positive terminal.
IN-Solar negative terminal.
OUT+Battery positive terminal.
OUT-Battery negative terminal.
SOLAR VOLTAGEPhotovoltaic cell maximum power point tracking pin. Short the connections on pin that corresponds to the voltage that your panel produces.
ℹ️
In maximum power point tracking status, the MPPT pin’s voltage is regulated to 1.205V.

Dimensions​

  • Board Dimensions: 54 × 38 mm (2.1 × 1.5 inch)
  • Header Pin Holes: 1.5 mm
  • Screw Holes: Designed for M3 screws (3.2 mm diameter)
  • Soldered boards are LEGO-compatible! 🧱

Jumper Details​

This board contains hardware jumpers. See below for their locations and functions:

jp1
JP1
JumperDefault StateFunction
JP1NC (Normally closed)Connects PWR LED

Hardware repository​

Schematics, KiCad files, Gerber files, and more can be found in the GitHub repository:

MPPT Li-Ion CN3791 charger board Hardware Design

GitHub hardware repository for this product

The hardware repository contains everything you need to understand, modify, or manufacture the board. The various output folders are versioned. You can check which board version you have specifically by finding the version mark on the PCB.

Below is an overview of the available files.

CAD files​

We use KiCad, an open-source PCB design tool. You can open and edit the .kicad_pro project file, which includes both the schematic and PCB layout.

The PANEL files are used internally for production.

Schematic​

The OUTPUTS folder contains the schematic in .pdf format, exported from KiCad.

BOM (Bill of Materials)​

The bill of materials (BOM) is provided in two formats:

  • A standard .csv table, listing all components, part numbers, and values.
  • An interactive BOM (.html) that visually highlights each component on the PCB, making it easy to locate and reference parts.

3D files​

A 3D model of the PCB is available in .step format, allowing you to inspect the board design in CAD software.

Gerber files​

Gerber files are essential for PCB manufacturing, as they contain precise instructions for each layer of the board. The repository includes standard Gerber outputs in a .zip file, such as:

  • Copper layers (.Cu.gbr) – Defines the traces and pads on the board.
  • Solder mask layers (.Mask.gbr) – Specifies the protective solder mask.
  • Silkscreen layers (.Silkscreen.gbr) – Contains text and component markings.
  • Paste layers (.Paste.gbr) – Used for stencil fabrication in SMD assembly.
  • Drill files (.drl) – Provides drilling coordinates for vias and holes.
  • Board outline (.Edge_Cuts.gbr) – Defines the shape of the PCB.
  • Gerber job file (.gbrjob) – Describes the set of Gerber files used for production.

These files are ready for fabrication and can be used in PCB manufacturing.

Compliance​

The Compliance section includes important regulatory and safety documentation for this product. These files ensure compliance with relevant industry standards and legal requirements.

  • CE – Certification document confirming compliance with EU safety, health, and environmental requirements.
  • UKCA – UKCA (UK Conformity Assessed) certification for the UK market.
  • Safety Instructions – Safety guidelines and precautions provided in English and German.
  • Info.txt – Contains product details such as SKU, country of origin, HS tariff code, and barcode.