Solar-Powered GPS Tracker: France to Turkey Journey

The Journey

We launched a high-altitude balloon from France that traveled 2,847 kilometers before landing in Turkey. The flight lasted 55 hours and 10 minutes (2 days and 7 hours). The payload transmitted GPS coordinates via LoRaWAN, powered entirely by solar charging with supercapacitor storage.

Hardware: Heltec HTCC-AB02S CubeCell

Why this board: The HTCC-AB02S integrates everything needed for a GPS tracker in one compact package: ASR6052 chip (ARM Cortex M0+ plus SX1262 LoRa radio), built-in GPS module, and onboard solar charging system.

Weight optimization: We desoldered the 0.96-inch OLED display. It's useless on a balloon 7.7km up, and removing it saved precious grams. Every gram matters for altitude and flight duration.

Key specs:

• ASR6052: Combined MCU + LoRa radio chip
• Built-in GPS module (AIR530Z variant)
• Onboard solar charging circuit (supports 5.5-7V panels)
• Ultra-low power: 21µA deep sleep current
• 868MHz LoRaWAN (EU frequency)
• Dimensions: Compact enough for balloon payload

Why Solar Power with Supercapacitors

At altitude, temperatures drop significantly. The balloon reached 7,768 meters where temperature hit -29.3°C. The payload experienced temperature extremes from -29.3°C at altitude to +40.3°C at ground level. Lithium batteries struggle across this temperature range - internal resistance increases at cold, capacity degrades at heat.

Supercapacitors work from -40°C to +70°C without degradation. Charge/discharge cycles are unlimited. Combined with solar charging, they provided continuous power through the entire 55-hour journey.

The 3W panel generated enough current even through thin clouds to keep supercapacitors charged during day/night cycles.

What Worked

Power System

The HTCC-AB02S's onboard solar charging circuit plus external supercapacitors worked perfectly. Voltage never dropped below 6.8V even during the longest night (14 hours at high latitude).

Solar panel pulled 180-240mA during peak sun - more than enough to offset the GPS + LoRa transmitter draw. During night periods, supercapacitors provided storage without the temperature limitations batteries have at -29.3°C.

LoRaWAN Coverage

SF12 (maximum range spreading factor) with 14dBm transmit power. Coverage exceeded expectations:

• Maximum altitude reached: 7,768 meters
• 3,309 packets successfully received across the entire flight
• Thousands of Helium hotspots received packets during the journey
• Maximum distance to receiving hotspot: 511 km
• Mean travel speed: 50 km/h

The Helium network's extensive coverage meant the balloon was continuously tracked as it drifted across borders. High-altitude LoRaWAN testing is rare - this flight provided real-world data showing extreme range capabilities (511 km!) and how many gateways can receive a single moving device.

Telemetry Data

The payload logged:

• GPS position throughout flight
• External temperature: -29.3°C at max altitude (7,768m), +40.3°C at ground level
• Temperature swing: 69.6°C total range from coldest to hottest
• Barometric pressure: 388 hPa at max altitude, 1013 hPa at sea level
• Supercapacitor voltage and solar current each transmission
• GPS fix quality and satellite count
• Mean travel speed: 50 km/h across 2,847 km journey
• Total packets transmitted and successfully received: 3,309

How Helium Network Enabled This Flight

The Helium network's distributed infrastructure made continuous tracking across 2,847 km possible. Thousands of hotspots received the 3,309 transmitted packets during the 55-hour journey - far more coverage than any single organization could deploy.

Extreme range achieved:

• Maximum distance to receiving hotspot: 511 km
• Single packet reached 852 hotspots
• Altitude advantage: 7,768m line-of-sight enabled extreme ranges

Why Helium worked:

• Community-operated gateways meant coverage in rural areas where commercial networks don't exist
• No roaming fees or border crossing issues - one LoRaWAN network across multiple countries
• Hotspot owners participated in tracking - seeing packets from a moving balloon at 7,768m was novel

Network effect: At 50 km/h average speed, dozens to hundreds of hotspots received each packet, providing massive redundancy. If one gateway missed a packet, countless others captured it.

Public tracking: Helium's blockchain recorded every packet reception. This created a public, verifiable trail of the balloon's path. Anyone could see which hotspots received packets and when, enabling real-time community tracking without centralized infrastructure.

Community Response

Flight path data got shared across LoRaWAN communities in 4 countries. Turkish LoRa enthusiasts tracked the landing and helped with recovery coordination. The Helium network's open data meant multiple people could follow the journey in real-time, increasing chances of successful recovery.

Complete Hardware List

Main board:

• Heltec HTCC-AB02S CubeCell GPS-6502 (868MHz)
• OLED screen desoldered for weight reduction
• ASR6052 chip (ARM Cortex M0+ + SX1262 LoRa)
• Integrated GPS module

Power system:

• 3W 6V polycrystalline solar panel
• Supercapacitors for energy storage (-40°C to +70°C rated)
• HTCC-AB02S's onboard solar charging circuit

Antenna:

• Custom 868MHz antenna design from Aliexpress
• Tuned with NanoVNA for optimal impedance match

LoRaWAN settings:

• SF12, BW125, CR4/5 (maximum range configuration)
• 868MHz EU band

Lessons Learned

What worked better than expected:

• Supercapacitors handled -29.3°C to +40.3°C temperature swings (69.6°C range) without issues
• Solar charging maintained power even through clouds
• Extreme LoRaWAN range: 511 km maximum distance to receiving hotspot
• Thousands of Helium hotspots provided continuous coverage across 2,847 km
• 3,309 packets successfully transmitted and received
• HTCC-AB02S integration simplified design - no separate GPS wiring
• Desoldering the screen was worth it for weight savings

What we'd change:

• Add backup GPS or redundant fix attempts - lost position twice over dense cloud cover
• Increase transmission frequency to 5 minutes during ascent/descent phases
• Use larger balloon - descent was faster than calculated

What this proved: Solar + supercapacitors + LoRaWAN handles conditions that challenge cellular or satellite trackers. Temperature range from -29.3°C to +40.3°C (69.6°C swing) at 7,768m altitude. 55 hours continuous operation across 2,847 km. Mean speed 50 km/h. 3,309 packets transmitted. Maximum range 511 km. Total hardware cost: under €50.

The Helium network's distributed coverage made this possible - thousands of hotspots provided redundant tracking across borders. No single organization could deploy equivalent infrastructure.

The HTCC-AB02S is designed for exactly this kind of application - integrated GPS/LoRa/solar charging eliminates wiring and reduces failure points. Desoldering unnecessary components (display) optimizes for the specific use case.