The CN3791-based module is an MPPT (Maximum Power Point Tracking) solar charger designed to efficiently charge a single-cell Li‑ion/LiPo battery from a nominal 12 V solar panel. It combines a high-frequency buck converter with lithium charging management and protection in a compact board with JST connectors.
Electrical Specifications
- Input Voltage (Solar Panel): Designed for panels with a nominal 12 V - actual range ~6–15 V depending on variant and resistor setting.
- Operating Input Range (IC): 4.5–28 V at the CN3791 chip level
- Maximum Charge Current: Up to 2 A for the 12 V module version
- Switching Frequency: Around 300 kHz for efficient MPPT control
- Output Charge Voltage: 4.2 V ±1 %, constant-voltage regulation for Li-ion chemistry
- Trickle Charge: If battery is deeply discharged (< ~2.8 V), pre‑charging engages at ~17.5 % of full current
- Charge Termination: Ends when current drops to ~16 % of maximum, auto-restarts if battery drops below ~95.5 % of 4.2 V
- MPPT Regulation: Keeps panel voltage at its maximum power point by regulating MPPT pin to 1.205 V via resistor divider
- MPPT Efficiency: Typically high, up to ~98 % on the IC level.
Protection & Control
- Under-voltage Lockout: Prevents operation when panel voltage falls below battery voltage
- Battery Over-voltage Protection: Stops charging once target voltage reached
- Charge Status Indicators: Dedicated CHRG (charging) and DONE (complete) open-drain outputs—often wired to LED
- Soft Start: Gradual charge ramp-up to reduce inrush current.
- Auto Recharge: Re-initiates charge cycle when battery voltage dips after full charge
Mechanical & Interface Details
- Connectors: Pre-installed 2‑pin JST/PH2.0 ports for solar panel and battery—usually 4 connectors for easy setup
- Size: Approx 45 × 20 × 9.5 mm
- Weight: Around 7–10 g depending on version.
- Temperature Range: –40 °C to +85 °C, suitable for outdoor conditions.
Quick Specs Table
Feature | Specification |
|---|---|
| Designed Panel Input Voltage | 12 V nominal (module), CN3791 IC: 4.5–28 V |
| Max Charge Current | 2 A |
| Switching Frequency | 300 kHz |
| Charge Voltage | 4.2 V ±1 % |
| Trickle Charge | ~17.5% of full current |
| Charge Termination | ~16% of full current |
| MPPT Control Voltage | MPPT pin regulated at 1.205 V |
| Temperature Range | –40 °C to +85 °C |
| Size (mm) | 45 × 20 × 9.5 |
| Weight (g) | 7–10 |
| Connectors | 2‑pin JST/PH2.0 |
Use Cases
- Ideal for small solar setups to charge a single-cell battery (3.7 V nominal).
- Great for DIY solar power banks, solar garden lights, remote sensors, or portable energy systems.
- High MPPT efficiency ensures maximum energy harvest across varying sunlight.
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