Solar-Powered Meshtastic Node Troubleshooting

My Node Dies Overnight

Check battery capacity first. A typical 18650 (2500–3500 mAh) powers a Meshtastic node for 12–24 hours without solar. You need enough battery to last through darkness.

Battery	Capacity	Node Runtime (no solar)
1× 18650 3500mAh	12.95 Wh	12–18 hours
2× 18650 (parallel)	25.9 Wh	24–36 hours
21700 5000mAh	18.5 Wh	16–24 hours
LiFePO4 6Ah	19.2 Wh	18–26 hours

Formula: runtime_hours = battery_Wh / node_power_W Typical Meshtastic node: 0.5–0.8W (ESP32 + GPS + display).

Solar Panel Too Small

Region	Sun Hours/Day	Panel Size for 24/7
Northern EU	3–4	5–10W
Central EU	4–5	3–5W
Southern US	5–6	2–3W
Cloudy/rainy region	2–3	8–15W

Rule of thumb: Panel wattage should be 3–5× node power consumption for reliable 24/7 operation.

Charge Controller Problems

1. TP4056 only charges to 4.2V — fine for Li-Ion, but has no temperature protection. In direct sun, battery can overheat.
2. No under-voltage protection — if battery drops below 2.5V, TP4056 will not restart charging. You need a protected cell or a BMS.
3. Solution: Use a dedicated solar charge controller like CN3791 or bq24650. These handle MPPT, temperature, and low-voltage recovery.

GPS Draining Battery

GPS consumes 30–50mA continuously. On a solar node:

1. Set position.gps_enabled = false if you do not need real-time tracking
2. Set position.position_broadcast_secs = 900 (15 min) instead of default
3. Use position.fixed_position = true for stationary nodes

Wiring Checklist

Solar Panel (+) ─── Schottky diode ─── CN3791 IN+
Solar Panel (-) ───────────────────── CN3791 IN-
CN3791 BAT+ ─── 18650 (+) ─── BMS ─── ESP32 VIN
CN3791 BAT- ─── 18650 (-) ─── BMS ─── ESP32 GND

• Always use a Schottky diode between panel and charger (prevents reverse current at night)
• Always use a BMS-protected cell or external BMS board
• Add a 0.1µF ceramic + 100µF electrolytic capacitor near the ESP32 VIN pin

Related

• Meshtastic Guide
• LoRa Device Selection