Nokia Lumia 950 XL Replacement Battery BV-T4D 3.9V 2950mAh

Nokia Lumia 950 XL — 3.9V Li-ion Replacement Battery (BV-T4D)

This is a 3.9V Li-ion replacement cell rated at 2950mAh (11.51Wh), built to the BV-T4D specification. It fits the Lumia 950 XL, Lumia 950 XL Dual SIM, and Cityman variants. If your original cell has degraded, swells, or no longer holds a charge through a normal day, this is the direct swap.

• Lumia 950 XL and Cityman compatibility: All three variants — standard, Dual SIM, and Cityman — share the same battery bay dimensions and BV-T4D connector footprint. The BMS handshake and NFC-adjacent pad layout are identical across the lineup, so one cell covers all three.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a Lumia 950 XL unit. The BMS accepted charge current correctly, thermal reporting stayed within normal range, and the USB-PD fast charge protocol engaged without error flags after the first calibration 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 — preventing false percentage readings from the first day.

Sudden shutdown at 20–30% on the Lumia 950 XL replacement cell

This is a voltage cliff issue, not a capacity problem. When the modem fires up for a call or the screen hits full brightness, current draw spikes sharply. A new cell that hasn't been calibrated yet may sag below the BMS cutoff threshold — around 3.0V under load — even though the fuel gauge still shows 20–30% remaining. The fix is one full uninterrupted discharge-charge cycle with fast charging disabled. After that cycle, the coulomb counter aligns to the actual cell curve and the shutdowns stop.

USB-PD fast charge not working on first cycle after replacement

After a cell swap, the Lumia 950 XL's charge IC sometimes refuses to negotiate the USB-PD fast charge contract on the first cycle. The BMS on a new, fully uncalibrated cell presents a different impedance profile than the aged cell it replaced, which causes the charge IC to fall back to standard 5V charging as a safety measure. Let the phone complete one full charge on a standard 5V USB source before switching back to the fast charger. Once the BMS has completed that first cycle, fast charge should negotiate normally — confirm by checking that the phone reports "charging rapidly" in the lock screen status.