BL-5CV Vertu Ascent 2010 Replacement Battery 3.7V 1200mAh

Vertu Ascent 2010 / Signature S Design — 3.7V Li-ion Replacement Battery (BL-5CV)

This is a 3.7V, 1200mAh Li-ion cell that replaces the original BL-5CV battery in the Vertu Ascent 2010, Vertu X, and Signature S Design. These phones share the same battery bay and connector format, making one cell compatible across the group. Capacity figures come from product data, not inflated aftermarket claims.

• Ascent 2010, Vertu X, and Signature S Design compatibility: All three models run the same 3.7V battery rail and use identical physical contact layout and BMS handshake protocol. A single BL-5CV cell services all of them without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, confirming the BMS accepts the cell without triggering a protection cutoff. Charge termination and temperature monitoring responded correctly across the test cycle.
• Fuel gauge recalibration on first use: After fitting this cell, run one full discharge to near-empty, then charge uninterrupted to 100% before enabling fast charging. The phone's fuel gauge IC calibrates its discharge curve during this first cycle — skipping it leaves the coulomb counter reading against stale data from the old cell.

Why the Ascent 2010 reports wrong battery percentage after a cell swap

The fuel gauge IC in the Ascent 2010 builds its percentage estimate from a stored discharge curve tied to the old cell's impedance profile. When you fit a new cell, that curve no longer matches actual cell behaviour. The IC keeps counting against outdated reference points, so the percentage shown can be several points off from real capacity. One full discharge-charge cycle lets the coulomb counter reset against the new cell and corrects the readout.

Sudden shutdown at 20–30% on the Vertu Signature S Design

This happens when the cell voltage drops below what the modem and display draw can sustain under load, even though the fuel gauge still shows charge remaining. The BL-5CV cell hits a voltage cliff — actual terminal voltage collapses under peak current while the reported percentage hasn't caught up. It is not a faulty cell; it is an uncalibrated gauge reading a new cell curve. Run the device down fully until it shuts off on its own, charge to 100% without interruption, and the fuel gauge IC will map the correct cutoff voltage — typically around 3.2V under load.