CN3791 solar charge controller - MPPT, 1S Li-Ion, 4.5-28 V

Product Overview

• MPPT solar charger module for a 1S Li-Ion/LiPo cell (3.7 V nominal, 4.2 V charge termination)
• Input voltage range from 4.5 to 28 V, suitable for various types of solar panels
• Constant-current/constant-voltage charging with automatic precharging and cyclic charging
• MPPT control at 1.205 V for the panel’s optimal operating point
• Four JST-PH double connectors (two for the panel, two for the battery) plus solder pads
• Status LEDs for charging and charging complete
• Automatic shutdown at low input voltage and standby mode without panel voltage

Product Description

The module charges a single lithium-ion or lithium-polymer cell directly from a solar panel. It regulates the panel voltage using pulse-width modulation so that the panel operates close to its optimal operating point, where it delivers the most energy. The voltage at the integrated control pin is stabilized at 1.205 V; an externally connected resistor divider determines the actual panel voltage at which this ideal point is reached.

Charging takes place in several stages. When the cell is deeply discharged, the module starts with reduced precharging. As soon as the cell voltage exceeds a defined threshold, it switches to constant-current charging. As the voltage approaches the final value of 4.2 V, the current continuously decreases until charging is complete at a low residual current. If the battery voltage later falls below a defined value, a new charging cycle starts automatically without manual intervention.

Four identical JST-PH connectors are available for connection, with two on opposite sides for the solar input and battery output. Since they are internally connected in parallel, additional cables, a second panel, or other consumers can be connected directly without requiring splitters. Four solder pads on the circuit board alternatively allow direct wiring of the panel, battery, and ground. Two LEDs indicate whether charging is in progress or complete.

The module switches off automatically when the input voltage falls below the permitted range and enters a low-power standby mode when no panel voltage is present. Excessive battery voltage stops the charging process to protect the cell. The input voltage range from 4.5 to 28 V allows use with various types of panels; however, a solar panel with sufficient output is required for operation, as the module cannot use any other power source.

Safety Information

Check the polarity when connecting the panel and battery; incorrect polarity will cause damage. The module is not intended for integration into household electrical installations and is intended exclusively for building prototypes and for testing and development purposes. Work on or in the immediate vicinity of electrical installations must be carried out by qualified electricians; consult a qualified electrician if you have any questions about commissioning.

Scope of Delivery

• 1× CN3791 MPPT solar charger module (for 1S Li-Ion/LiPo)