Nokia Lumia 950 XL Replacement Battery BV-T4D 3.85V 3350mAh

Nokia Lumia 950 XL — 3.85V Li-ion Replacement Battery (BV-T4D)

This is a 3350mAh, 3.85V Li-ion cell replacing the OEM BV-T4D in the Nokia Lumia 950 XL, Lumia 950 XL Dual SIM, and Cityman. It slots into the removable battery compartment and connects to the same BMS contact points as the original. Capacity is 3350mAh (12.9Wh) — matching OEM spec.

• 950 XL and Cityman platform fit: The Lumia 950 XL and its Dual SIM variant share the same battery bay dimensions, contact layout, and BMS handshake protocol — this cell covers all three. The Cityman codename uses the identical hardware platform, so compatibility carries across without modification.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on the 950 XL. The BMS accepted the charge handshake on the first connection, the Qualcomm Quick Charge circuit engaged normally, and the fuel gauge IC tracked voltage across the full discharge curve without reporting anomalies.
• Fuel gauge recalibration on first cycle: After installation, disable fast charging for the first complete discharge-charge cycle. The fuel gauge IC on the 950 XL is calibrated to the old cell's discharge curve. Running one slow cycle lets the coulomb counter recalibrate against the new cell before high-current charging is applied to an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC still holds the discharge curve of the degraded original cell in memory. When the replacement cell's actual voltage drops below the old curve's predicted threshold — typically around 3.6V under modem or display load — the phone interprets it as a critical low and cuts power. The fix is a full uninterrupted discharge to 0% followed by a complete charge to 100%, which forces the IC to rewrite its curve. After one cycle, shutdowns at 20–30% stop in most cases.

USB-PD fast charge not working after cell swap

On the first charge cycle after fitting a new cell, the 950 XL's charge IC sometimes refuses to negotiate the USB-PD fast charge handshake because it detects a high-impedance cell — a characteristic of a new, uncharged Li-ion cell at rest. The device falls back to standard 5V charging until the cell has been partially conditioned. Plug into the OEM charger or a USB-PD charger and allow one full standard-rate charge cycle to complete. Fast charging typically resumes from the second cycle onward.