Rollei 10050 Compatible Battery 3.7V 750mAh Li-ion

Rollei 10050 Series — 3.7V Li-ion Replacement Battery

This is a 3.7V, 750mAh (2.78Wh) lithium-ion cell for the Rollei 10050, 10051, 10052, 10053, and compatible models. It replaces a degraded or failed original cell in these compact smartphones. Dimensions are 46.20 × 34.14 × 5.68mm — verify against your existing cell before installation.

• Rollei 10050 series compatibility: These models share the same physical footprint, voltage rail, and connector orientation, which is why one cell covers the full range. The BMS on each device communicates over the same two-wire interface, so no protocol mismatch occurs across the series.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes, monitoring BMS handshake, charge acceptance, and cutoff behaviour at both ends of the voltage window. The cell held stable at 3.7V nominal with no anomalous cutoffs during the discharge phase.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still reading percentage from the old cell's discharge curve, not the new one. The new cell hits its actual voltage floor earlier than the IC expects, and the device cuts out before the displayed percentage reaches zero. It is not a faulty cell — it is a calibration mismatch. Run one full discharge to automatic shutdown, then charge uninterrupted to 100% to let the coulomb counter reset against the new curve.

Phone reports wrong battery percentage after cell swap

The fuel gauge IC stores learned capacity data from the original cell. After a swap, those stored values no longer match the new cell's actual charge-discharge behaviour, so percentage jumps erratically or reads high when the device is nearly flat. The fix is one full uninterrupted cycle — drain the phone until it shuts off automatically, then charge to 100% without interruption. After that single cycle the IC recalibrates and percentage tracking stabilises.