SFR Startrail 5 Compatible Battery 3.8V 2000mAh 178067700

SFR Startrail 5 — 3.8V Li-ion Replacement Battery (178067700)

This is a 3.8V, 2000mAh Li-ion battery for the SFR Startrail 5 smartphone. It fits the Startrail 5 directly, using OEM part number 178067700. Install it when the original cell no longer holds a usable charge or has failed outright.

• Startrail 5 fit: The Startrail 5 uses a single-cell 3.8V Li-ion pack with a specific connector pinout and BMS communication line. This replacement matches that pinout, so the phone's charge IC and fuel gauge IC can talk to the cell correctly from first power-on.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench and monitored BMS handshake, cutoff voltage, and charge IC acceptance. The cell accepted charge without fault codes and the BMS held cutoff at the expected lower threshold.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve for the new cell before high-current charging pushes current into an uncalibrated state.

Why the Startrail 5 reports wrong battery percentage after a cell swap

The Startrail 5 uses a fuel gauge IC that stores a learned discharge curve from the old cell. When a new cell goes in, that stored curve no longer matches the actual cell chemistry and capacity. The result is percentage readings that jump, stall, or plateau at values that don't reflect real charge state. One full discharge-charge cycle without fast charging gives the IC enough data to reset its coulomb counter and build a new curve against the replacement cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically during a call, screen-on navigation, or mobile data activity — faster than the fuel gauge IC predicted. The IC still shows 20–30% remaining, but the cell voltage has already fallen below the BMS cutoff threshold, so the phone shuts off. It is not a faulty battery. Run two full discharge-charge cycles to let the fuel gauge recalibrate the voltage-to-percentage mapping. After calibration, shutdowns at that percentage range should stop.