Xiaomi BM45 Redmi Note 2 Replacement Battery 3.85V 3020mAh

Xiaomi Note 2 Premium Edition — 3.85V Li-ion Replacement Battery (BM45)

The BM45 is a 3020mAh, 3.85V Li-ion cell that powers the Xiaomi Redmi Note 2 Premium Edition and Note 2 Premium Edition Dual SIM (model 2015213). This replacement restores full battery function when the original cell has degraded, swollen, or stopped holding a usable charge. Capacity is 11.63Wh — matching the original specification.

• Note 2 Premium Edition compatibility: The BM45 fits both the standard and Dual SIM variants of the Note 2 Premium Edition. Both share the same battery bay dimensions (81.60 × 64.90 × 4.20mm), connector pinout, and BMS handshake protocol — one cell covers the full model range.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Note 2 platform. The BMS accepted the cell without error flags, charge termination triggered correctly at 4.35V, and voltage under modem load stayed above the OS shutdown threshold through a full discharge.
• Fuel gauge recalibration on first use: After installation, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% before using the device. This lets the coulomb counter IC map the new cell's discharge curve accurately — skipping this step causes the OS to report incorrect percentages for several days.

Sudden shutdown at 20–30% on the BM45 replacement cell

The Redmi Note 2 shuts down when cell voltage drops below roughly 3.4V under load — not when the reported percentage hits zero. A new cell with an uncalibrated fuel gauge IC can show 25% remaining while the actual cell voltage collapses under combined modem, screen, and processor draw. The OS sees a voltage cliff and triggers an emergency shutdown. One full discharge-charge cycle recalibrates the coulomb counter so reported percentage tracks real cell voltage. After calibration, the 3.0V cutoff threshold aligns with the gauge and shutdowns at non-zero percentage stop.

Fast charging not working on the first cycle after installation

On first connection to a fast charger, the Note 2's charge IC runs a qualification handshake with the new BMS before accepting elevated current. If the BMS hasn't completed its initialisation sequence — which requires the cell voltage to be above approximately 3.0V — the charger falls back to standard 5V/1A. Charge the phone once at standard speed to bring the cell above 3.5V, then reconnect the fast charger. The handshake completes and elevated charging resumes from the second cycle onward.