Bird SC01 Replacement Battery 3.7V 850mAh Li-ion

Bird SC01 / C01 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 850mAh Li-ion cell for the Bird SC01 and C01 smartphones. It fits both models directly and restores power when the original cell has degraded or failed. Voltage and capacity match the original spec — 3.7V nominal, 850mAh (3.15Wh).

• SC01 and C01 compatibility: Both models run the same voltage rail and share the same connector pinout and BMS handshake, which is why a single cell covers both. Swapping between them needs no wiring change or adapter.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS cutoff thresholds at both ends. The protection circuit tripped correctly at low-voltage cutoff and accepted a full charge without thermal events.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map its readings against the new cell's actual discharge curve before high-current charging is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the Bird SC01 after a cell swap

This happens because the fuel gauge IC is still running the discharge curve it learned from the old, degraded cell. When the new cell hits a voltage point that the IC reads as 20–30%, the actual cell voltage under modem or screen load drops sharply — faster than the IC expects. The phone interprets this as a fault and shuts down to protect the hardware. One full discharge-charge cycle without fast charging resets the coulomb counter and clears this behaviour.

Phone warm near the battery during the first charge after replacement

A new cell typically has higher internal impedance than a broken-in one. During the first charge, the charge IC pushes current into a cell with more resistance than it was calibrated to expect, which produces mild heat. This is normal on cycle one and reduces after the cell's impedance settles. If warmth persists past the second charge cycle, check that the charge IC is not locked into a high-current profile — drop to a 5W standard charger and verify the temperature drops.