25W Mini Solar Panel with Built-in MPPT Controller
25W Solar Power Box with Built-in MPPT Controller and 18650 Battery Bay
The 25W mini solar panel is a compact off-grid power solution with a built-in MPPT (Maximum Power Point Tracking) controller and selectable 5V/6V/9V/12V DC output. It is designed for small low-voltage systems that need better charging performance, stable output, and easier integration in outdoor installations.
The integrated MPPT charge controller optimizes charging efficiency compared with basic charging circuits under changing sunlight conditions — the practical difference is largest in diffuse light and winter sun, which is exactly when a small system runs short. The trade-off between the two controller types is broken down in our guide to MPPT vs PWM for mini and small solar systems.
With a high-efficiency 25W monocrystalline module, support for up to six 18650 batteries (not included), and clear LED status indicators, this 25W solar panel is designed to make small solar systems simple, efficient and easy to monitor. The IP66 housing, waterproof button switch and included mounting bracket make it well suited to outdoor use.
Will it run your device?
The specification table below tells you what the unit is. This table tells you what it does. Figures are estimates derived from the rated specification plus typical device draw; confirm against your own datasheet before you commit to a deployment.
| Load | Typical draw | Runtime on a full pack, no sun | Sustainable on the 25W module? |
|---|---|---|---|
| 4G outdoor camera, streaming continuously | 3–5W | Approx. 11–18 hours | Marginal — fine in summer, short in winter |
| 4G camera, event-triggered with idle standby | 0.5–1.5W average | Approx. 1.5–4.5 days | Yes |
| LoRa / LoRaWAN sensor node, duty-cycled | 0.1–0.3W average | Approx. 8–23 days | Yes, with wide margin |
| Microcontroller weather station, duty-cycled | 0.05–0.2W average | Approx. 12 days and up | Yes, with wide margin |
| 12V load drawing the full rated 1A | 12W | Approx. 4.5 hours | No — exceeds a clear day of harvest |
Two things decide whether a small solar build survives its first winter: the average draw of the load, not its peak, and the number of peak sun hours in the worst month of the year rather than the annual average. Sizing methods for the common cases are covered in solar power for security cameras and sensors and, for microcontroller builds, why 5V solar panels kill ESP32-C3 weather stations.
Details & Specs
| Item | Specification |
|---|---|
| Solar Panel Type | Monocrystalline silicon |
| Rated Power | 25W |
| Conversion Efficiency | Approx. 23% |
| MPPT Charging | Yes, conversion efficiency improved by about 20% |
| Panel Output Voltage | Approx. 17.5V under load; approx. 21V open circuit |
| Panel Output Current (max) | Approx. 1.2A |
| Power Adapter Charging | Supported |
| Battery Type | 18650 lithium batteries (supports KC batteries) |
| Maximum Battery Quantity | Up to 6 pcs |
| Battery Connection | Parallel |
| Single-Cell Capacity | Supports cells up to approx. 3300mAh |
| Total Pack Capacity | Supports up to approx. 19800mAh (6 × 3300mAh), batteries not included |
| Full Charge Time | Approx. 4 hours (under strong sunlight, typical conditions) |
| Cell Internal Resistance | For 6 cells, internal resistance difference recommended ≤ 0.1–0.2% |
| Minimum Starting Battery Quantity | 1 pc |
| Overcharge Protection Voltage | Approx. 4.28V per cell |
| Overdischarge Protection Voltage | Approx. 3.3V per cell (output stops); approx. 3.0V hardware cutoff |
| Balanced Charging | Supported |
| Charging Voltage Requirement | 16V < charging voltage < 21V |
| DC Output Voltages | 5V / 6V / 9V / 12V |
| DC Output Currents (rated) | 5V 2A / 6V 1.5A / 9V 1.2A / 12V 1A |
| Output Connector Type | 5.5 × 2.1 mm DC output (default) |
| Working Humidity | ≤ 90% RH |
| Ingress Protection | IP66 |
| Weight | Approx. 1.25 kg (excluding batteries) |
| Package Size | Approx. 48 × 29 × 7 cm |
Note: 18650 batteries are not included. For best performance, use cells with similar capacity and internal resistance as recommended.
How to Use
- Install 1–6 compatible 18650 batteries in the battery compartment, observing the correct polarity and using cells with similar capacity.
- Mount the 25W solar panel using the included bracket and angle it toward the sun to maximize exposure.
- Connect your 5V–12V device to the 5.5 × 2.1 mm DC output and select a suitable voltage within 5V/6V/9V/12V on your system if applicable.
- Allow the panel to charge the battery pack in strong sunlight; under typical conditions, a fully matched pack can reach full charge in about 4 hours.
- When needed, you can charge the battery pack through a suitable external power adapter that meets the specified charging voltage range.
Who It’s For
This 25W solar panel suits DIY users, hobbyists and small off-grid projects that need a reliable 5–12V power source — low-power electronics, test benches, experimental setups and any situation where running mains power is inconvenient or unavailable.
It is also a practical evaluation unit for product teams: buy one, run your own load on it for a week, and confirm the energy budget before committing to a production design. If the deployment is a network of nodes rather than a single build, the field-sizing considerations are set out on our solar power for IoT sensors page.
Care & Maintenance
- Keep the solar surface clean and free from dust or shade to maintain efficiency.
- Use only quality 18650 cells and avoid mixing old and new batteries in the same pack.
- Try to match cells with similar capacity and internal resistance for more balanced charging and discharging.
- Ensure all covers and seals are properly closed to maintain the IP66 protection level in outdoor environments.
- If the panel will not be used for a long period, disconnect loads and store it in a dry place.
Custom and OEM versions
The stock unit ships as specified above. Where a product needs something the catalogue does not carry, the same platform can be rebuilt to your requirement: different panel wattage or output voltage, a different connector or cable length, an alternative battery configuration, custom enclosure dimensions, or your own branding and packaging.
- Panel voltages from 3V to 48V; custom outlines, cut-outs and laminates (PET, ETFE, fibreglass or glass).
- Samples of custom mini panels typically ship in 7–14 days; production is confirmed at quotation rather than promised in general terms.
- Components are sourced from ISO 9001, CE and RoHS certified partner factories, with pre-shipment QC evidence on every batch. We are a sourcing partner with factory-side QA, not a factory owner, and we say so up front.
- MOQ and pricing depend on the configuration — send the output specification and the quantity you need for a first batch and you get a manufacturable spec and a price at your volume.
More on what can be changed and what it costs: custom mini solar panels, and the OEM sourcing background in our mini solar panel for IoT sourcing guide. Looking for a bare panel instead of a complete box? See the mini solar panel range.
Not sure this box covers your load?
Send the average draw of your device, the reporting interval and the region it will be installed in. You get a sizing answer back within one working day — including an honest answer if a 25W unit is the wrong size for the job.
