Solar Panel & Charge Controller Selection

Solar Panel & Charge Controller Selection

Selecting the right panel and charge controller determines whether your solar node stays online year-round. This page covers available options and selection criteria.

Solar Panels

RAK Solar Panel 5V — $25

A small 5V panel designed for direct integration with RAK WisBlock builds and the RAK19012 module. Convenient if you are already using RAK hardware, but limited in output compared to generic monocrystalline panels.

RAK19012 Solar Module — $15

An all-in-one module combining USB-C input, solar input, and battery management with a built-in charge controller. Designed for RAK WisBlock systems. Simplifies the power system significantly — connect the solar panel and battery, plug the output into the WisBlock, done.

6W 6V Monocrystalline Panel — $15–$20

The community standard for DIY solar repeater builds. 6V panels work directly with CN3791 MPPT and TP4056 charge controllers without voltage regulation. Monocrystalline cells are more efficient per unit area than polycrystalline, particularly in low-light conditions.

• Output: 6W at peak sun
• Voltage: ~6V at maximum power point
• Size: Typically 180 × 130mm — fits on top of most enclosure sizes
• Daily harvest: 6W × 2.5–5 peak sun hours × 0.70 = 10.5–21 Wh/day depending on location and season

Charge Controllers

TP4056 — $2–$3

A basic single-cell Li-ion/LiPo charge controller with over-charge and over-discharge protection. Uses PWM (not MPPT) charging. The cheapest option and adequate for simple builds with moderate solar irradiance. A standalone TP4056 module does not have a load output — use the TP4056 with integrated DW01 protection IC, or add a separate protection module.

• Max charge current: 1A (set by resistor; default 1A modules are common)
• Input voltage: 4.5–8V (use with 5V or 6V panel)
• MPPT: No

CN3791 MPPT — $3–$5

A step up from the TP4056. The CN3791 implements Maximum Power Point Tracking (MPPT), which extracts more energy from the solar panel by continuously adjusting the operating point. More efficient than PWM charging, particularly under partial shading or variable irradiance. Recommended over TP4056 for serious solar builds.

• Input: 4.5–7V solar
• MPPT: Yes
• Charge current: Up to 2A
• Cost premium over TP4056: $1–$2 — worth it

Taidacent MPPT Module — $10

A slightly larger MPPT module with 1A charge current and 6V input support. Includes onboard voltage and current monitoring via LED indicators. Good choice when you want visibility into charge state without adding telemetry hardware.

RAK19012 All-in-One — $15

Integrated USB-C + solar + battery management for RAK WisBlock systems. Not suitable for non-RAK builds, but the simplest option for WisBlock deployments.

Charge Controller Comparison

Controller	Price	MPPT	Max Charge	Best For
TP4056	$2–$3	No (PWM)	1A	Budget builds; good sun locations
CN3791	$3–$5	Yes	2A	Most DIY solar repeater builds
Taidacent MPPT	$10	Yes	1A	When onboard monitoring is useful
RAK19012	$15	Yes	500mA	RAK WisBlock builds only

Panel Orientation and Mounting

• Face: South-facing in the northern hemisphere; north-facing in southern hemisphere
• Angle from horizontal: Match your latitude for year-round optimisation. For northern US (45–50°N latitude), 45–60° tilt. Steeper angles favour winter; shallower angles favour summer.
• Shading: Even partial shading of a small cell in the panel significantly reduces total output. Site the panel to avoid shading from trees, structures, or the node enclosure itself during peak sun hours.