MAX17043 LiPo Fuel Gauge
I2C battery fuel gauge that reports accurate state-of-charge — far better than voltage guessing.
Wiring & code for
MAX17043 practical reference
A single-cell fuel-gauge IC that reports accurate state-of-charge over I2C, far more reliable than estimating from raw voltage. Rather than just reading the battery's terminal voltage (which sags and recovers unpredictably under varying load), the MAX17043 uses a proprietary ModelGauge algorithm to track the cell's actual state of charge over time, giving a genuinely useful percentage reading for battery-powered projects — wearables, handheld devices, or anything that wants to show a realistic 'battery remaining' indicator rather than a rough voltage-based guess.
Key specifications
- Chipset: Maxim MAX17043 single-cell Li-ion/LiPo fuel gauge
- Operating voltage: 3.0V–4.2V DC (matches a single Li-ion/LiPo cell's voltage range directly)
- Operating current: ~50 µA typical, very low quiescent draw suitable for always-on battery monitoring
- Measurement: State-of-charge percentage (0-100%) via Maxim's ModelGauge algorithm, plus raw cell voltage
- Accuracy: No characterization or calibration required — works out of the box across most standard Li-ion/LiPo chemistries
- Interface: I2C, up to 400 kHz
- I2C address: 0x36 (fixed)
- Additional feature: Configurable low-battery alert via an interrupt output pin
Pinout and connection notes
This chip is specifically designed for single-cell (1S) Li-ion/LiPo batteries only and reads the cell voltage directly through its VDD pin rather than through a separate sense input, so it should be wired directly across the battery terminals (not through a regulator) for accurate readings; the ALRT pin can be used to trigger a low-battery warning or safe shutdown in software.
- VDD: Power, 3.0–4.2V DC (typically wired directly to the same single-cell battery being monitored)
- GND: Ground
- SCL: I2C clock line
- SDA: I2C data line
- ALRT: Low-battery interrupt output, configurable threshold
- QSTRT: Optional quick-start pin to force an immediate state-of-charge recalculation
Integration checklist
- Confirm the exact part number and breakout-board revision.
- Verify supply voltage, current demand, logic levels, and signal direction against the datasheet.
- Check controller pin assignments and bus address or interface mode against the example code.
- Power up with external loads disconnected, then test signals before full integration.
- If readings or communication fail, check power and ground first, then pin mapping, interface settings, and library initialization.
Troubleshooting and reproducibility
Record the board used, wiring, library/version, supply arrangement, and measured behavior. Use the selected board-specific wiring example as the source of truth. Never assume visually similar modules share identical voltage tolerance or pin order.