Solar Meshtastic Node Power Budget

[Pavel]

Short answer: Size a solar node from measured daily energy use, worst-month solar production, regulator loss and several days of battery reserve. Panel wattage alone is not a design because modem preset, GPS, telemetry, temperature and sleep behavior change consumption.

Before you start​

• Set the correct regional radio profile before testing; frequency plan, permitted power and duty-cycle constraints depend on location.
• Use the same modem preset, channel settings and channel key on nodes that are expected to communicate.

Step-by-step method​

1. Step 1: Measure current during sleep, receive, transmit and GPS acquisition, then calculate a 24-hour average from real duty cycles.
2. Step 2: Multiply average current by 24 hours for daily amp-hours and include regulator, charging and battery losses plus cold-temperature capacity reduction.
3. Step 3: Use local worst-month peak-sun-hours to size the panel, not summer marketing output. Add margin for shading, dirt and nonideal orientation.
4. Step 4: Choose protected battery capacity for at least three to five low-sun days where practical, then log voltage through cloudy weather before remote deployment.

Concrete example​

A node averaging 25 mA at 3.7 V uses about 0.6 Ah or 2.2 Wh per day before losses. With only two effective winter sun-hours and 60% end-to-end solar efficiency, a panel needs at least about 1.8 W merely to replace the average; practical margin suggests more.

How to judge the result​

The budget works when battery state recovers after normal days and remains above the safe cutoff through the chosen worst-case reserve period.

What to record​

• Record RSSI, SNR, hop count, delivery success and antenna height for a fixed route instead of quoting one maximum-distance message.
• Line of sight, Fresnel clearance and antenna placement usually improve range more effectively than additional transmit power.
• For solar nodes, calculate daily energy use and worst-month solar input, then include battery reserve for poor weather.

Common mistakes​

• Changing several hardware, software or RF variables at once, which removes the controlled comparison needed to identify the cause.
• Treating one autoscaled screenshot or one unusually good result as proof without recording the settings and repeating the test.
• Using battery label capacity at room temperature without regulator and winter derating produces an optimistic runtime estimate.

Final check​

Power-cycle both nodes and repeat the same bidirectional route test. Save region, preset, antenna, RSSI, SNR and delivery rate while keeping channel keys and precise locations private.