BL-T9 LG Nexus 5 Replacement Battery 3.8V 2300mAh

LG Nexus 5 D820 / D821 — 3.8V Li-Polymer Replacement Battery (BL-T9)

This is a 3.8V, 2300mAh lithium-polymer cell built to replace the original BL-T9 battery in the LG Nexus 5. It fits the D820 and D821 variants, both the 16GB and standard models. Voltage and capacity match OEM spec exactly.

• D820 and D821 compatibility: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The D820 is the North American band variant; the D821 covers global bands. Same cell, same fit.
• Bench tested on actual hardware: We cycled this cell in a D821 unit under mixed load — screen-on, LTE active, GPS polling. The BMS held charge termination correctly at 4.35V and cut off cleanly at the low-voltage threshold without triggering a hard shutdown loop.
• Fuel gauge recalibration after install: On first use, disable fast charging and run one complete discharge-to-charge cycle from 100% down to auto-shutdown, then charge uninterrupted to full. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins on an uncalibrated state-of-charge register.

Sudden shutdown at 20–30% on the replacement cell

The Nexus 5 fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that curve no longer matches the actual voltage-versus-capacity relationship. Under modem or display load, the cell voltage dips faster than the IC expects, triggering a low-voltage cutoff even though the reported percentage reads mid-range. Run one full discharge cycle without interruption — the coulomb counter resets and the shutdowns stop. Target a resting voltage of 3.85V at the 50% mark to confirm the recalibration is tracking correctly.

Device will not power on after sitting in storage

Lithium-polymer cells self-discharge in storage. If the cell drops below approximately 2.5V per cell, the BMS enters a protection lockout and blocks normal charging to prevent damage to an over-discharged cell. The phone shows nothing — no charging indicator, no boot screen. Connect to a wall adapter rated at 5V/1A or higher and leave it for 20–30 minutes without pressing the power button. The BMS recovery circuit trickle-charges the cell back above the lockout threshold, after which normal charging resumes.