Battery-Powered Wi-Fi Load Cell Data Logger with Cloud Connectivity
Battery-powered Wi-Fi data logger that samples a load cell every 3 minutes, uploads data to the cloud twice per day, and tracks battery state with a fuel gauge.
Intermediate Project
— This is intermediate because it combines low-power battery design, Wi-Fi connectivity, load-cell analog measurement, and fuel-gauge integration, all of which need careful power and firmware coordination.
Assumptions:
- The load cell is a standard bridge-type strain gauge load cell and will need an external load-cell amplifier/ADC front end.
- The prototype can tolerate a dev-board form factor rather than a custom ultra-low-power PCB.
- Cloud upload is intermittent, so the system can stay in deep sleep between measurements and wake for scheduled Wi-Fi sessions.
- Battery chemistry is assumed to be a single-cell Li-ion or LiPo pack, which matches the fuel-gauge parts listed.
Bill of Materials
Compatibility Notes
- The ESP32-C6-DEVKITC-1-N8, NAU7802, and ESP32-C6-DEVKITC-1-N8 all use low-voltage digital interfaces, so plan on a 3.3 V logic domain.
- The load-cell front end should be kept away from the Wi-Fi antenna and high-current power traces to reduce measurement noise during transmit bursts.
- A buck-boost regulator such as TPS63900DSKR is a good match for a single-cell battery because Wi-Fi current spikes can be large and the battery voltage will vary over discharge.
- If you use a dev board for the MCU, verify whether you will power the board through USB during development and through the battery/regulator in the final prototype; the power path should not back-feed the battery.
You'll Also Need
- Load cell itself and its mechanical mounting hardware.
- Battery pack, charger/protection circuit, and battery connector.
- Load-cell breakout board or the external resistors/passives needed around the NAU7802/HX711/ADS1232.
- Decoupling capacitors, pullups for I2C, and any level-shifting parts if your final design uses mixed-voltage peripherals.
- Enclosure, cable glands, strain relief, and mounting hardware for a real product prototype.
- Cloud firmware, backend endpoint, and data format definition (MQTT, HTTP, or HTTPS).
Estimated BOM Cost: $20-25 (based on live distributor pricing)
Design Considerations
Power Budget
The main power challenge is Wi-Fi, not the sensor readout. An ESP32-C6-DEVKITC-1-N8 board can draw tens to hundreds of mA during transmit, while deep sleep can be in the uA range on the bare module but much higher on a dev board because of USB-UART and regulator overhead. For a battery product, measure the actual sleep current of the assembled prototype early, because the dev board may not reflect final battery life.
Sampling Strategy
Reading the load cell every 3 minutes is easy, but you should average multiple ADC samples per wake cycle to reduce noise and drift. A practical pattern is wake, power the load-cell front end, wait for settling, take 8 to 32 readings, store the result, then go back to sleep. This reduces false changes caused by mechanical vibration and ADC startup transients.
Cloud Upload Reliability
Uploading only twice a day means you need local buffering for at least 12 hours of measurements, preferably more. Store timestamps and readings in flash or external storage so a missed Wi-Fi session does not lose data. Use a retry counter and a watchdog so the device can recover from AP outages or bad credentials without getting stuck awake.
Fuel Gauge Accuracy
The ESP32-C6-DEVKITC-1-N8 is useful for state-of-charge logging, but fuel gauges are only as good as the battery characterization and current profile assumptions. Expect the reported percentage to be approximate unless you calibrate the pack and account for temperature, load spikes, and aging. Log voltage, current, and state-of-charge together so you can spot drift over time.
Analog Layout
Load-cell measurements are sensitive to noise from the Wi-Fi radio and switching regulator. Keep the analog front end physically close to the load-cell connector, use a solid ground reference, and route the bridge signals as a tight differential pair. If possible, sample when the radio is off and avoid sharing noisy return paths with the RF and power stages.
Prototype-to-Product Path
A dev board is fine for proving the concept, but it will not give you the lowest power or the cleanest analog performance. Once the firmware and measurement chain are stable, move to a custom PCB with the ESP32-C6 module, the load-cell ADC, the fuel gauge, and a proper battery power tree. That is where you will recover battery life and improve measurement repeatability.
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