Nokia Lumia 550 Replacement Battery BL-T5A 3.8V 1900mAh

Nokia Lumia 550 / Lumia 730 Series — 3.8V Li-Polymer Replacement Battery (BL-T5A)

This is a 3.8V, 1900mAh (7.22Wh) lithium-polymer cell for the Nokia Lumia 550, Lumia 730, Lumia 735, and Lumia 735 Dual SIM, among others. It replaces OEM part numbers BL-T5A and BV-T5A. If the original cell no longer holds charge or the phone shuts down unexpectedly, this is a direct swap.

• Lumia 550 / 730 / 735 platform fit: These models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. At 82.40 × 40.00 × 5.20mm, the cell seats flush with no case pressure or connector misalignment.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Lumia 735. The BMS accepted charge from cold without triggering a protection cutoff, and the fuel gauge IC tracked cell voltage within normal tolerance across the full discharge curve.
• First-cycle calibration tip: After installation, disable fast charging and run one complete discharge-charge cycle before resuming fast charging. This gives the fuel gauge IC accurate data on the new cell's discharge curve before high-current charging begins pushing into an uncalibrated state.

Sudden shutdown at 20–30% on a replacement cell

This happens because the fuel gauge IC is still running calculations based on the old cell's internal resistance profile. When the modem fires up for a call or the display peaks in brightness, the new cell's voltage dips below the shutdown threshold faster than the gauge predicts. The phone reads 25% but the actual cell voltage under load is already at the cutoff point. One full discharge-charge cycle resets the coulomb counter and eliminates most of these premature shutdowns.

Phone won't power on after sitting in storage with a flat battery

Lithium-polymer cells that discharge below roughly 2.5V trigger a BMS lockout to prevent cell damage. The phone shows nothing — no logo, no charging animation — because the protection circuit is open. Connect the phone to a wall adapter, not a PC USB port, and leave it for 20–30 minutes without pressing the power button. The charge IC will slowly bring the cell back above the BMS recovery threshold, after which the phone should power on normally and show a low battery indicator.