Gigaset GS290 Replacement Battery 3.85V 4800mAh Li-Polymer

Gigaset GS290 — 3.85V Li-Polymer Replacement Battery (V30145-K1310-X475)

This is a 3.85V, 4800mAh Li-Polymer cell for the Gigaset GS290 smartphone. It replaces the original battery when the phone no longer holds a usable charge or shuts down unexpectedly. Capacity and connector position match the OEM specification (V30145-K1310-X475).

• GS290 fit: The GS290 uses a single-cell Li-Polymer pack with a low-profile 5.20mm thickness. This cell matches that form factor — 82.00 x 61.90 x 5.20mm — along with the correct connector orientation the phone's charge IC expects for BMS communication.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a GS290 unit. The BMS handshake completed without fault codes, and the charge IC accepted current at both standard and fast-charge rates after the first full cycle.
• 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 recalibrate against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Why the GS290 reports wrong battery percentage after a cell swap

The GS290 uses a coulomb counter tied to the fuel gauge IC. That IC builds its percentage model against the discharge curve of the original cell. When you install a new cell, the IC is still referencing the old curve — so percentage readings are off until it recalibrates. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% without using the phone. After that cycle, the gauge re-anchors to the new cell and percentage accuracy returns.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the phone's minimum threshold under load — typically during heavy modem activity, screen brightness peaks, or app processor bursts. The fuel gauge shows 25% but the cell can no longer sustain the voltage rail under that current draw. The BMS cuts output to protect the cell rather than let voltage sag further. Run two full calibration cycles and check that the reported shutdown voltage is above 3.4V — if it's cutting out above 3.6V, the cell needs a full recalibration cycle before the gauge tracks load voltage correctly.