BLU Tank 4.5 Replacement Battery 3.8V 1550mAh Li-ion

BLU Tank 4.5 — 3.8V Li-ion 1550mAh Replacement Battery

This is a 3.8V Li-ion battery rated at 1550mAh (5.89Wh) for the BLU Tank 4.5 smartphone. It replaces the original cell when the phone no longer holds a charge through a normal day of use. The physical footprint is 51.40 x 51.00 x 5.50mm — measure your current cell before ordering.

• Tank 4.5 fit: The Tank 4.5 uses a removable back panel with a swappable cell — no heat gun or adhesive required. The connector orientation and tab placement on this cell match the original dock point inside the battery bay.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Tank 4.5 unit. The BMS accepted charging current without flagging an error, and the fuel gauge IC began tracking state-of-charge correctly after one full cycle.
• Fuel gauge recalibration after swap: On first use, disable any power-saving fast-charge modes and run one complete discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC one clean reference cycle against the new cell's actual discharge curve before the OS starts using that data for percentage reporting.

Why the Tank 4.5 reports wrong battery percentage after a cell swap

The Tank 4.5 uses a fuel gauge IC that builds its state-of-charge model from previous discharge cycles stored in memory. When you swap in a new cell, that stored model no longer matches the new cell's voltage-to-capacity curve. The phone reads voltage and maps it against the old curve, so the percentage shown can be off by 10–20% — especially in the 30–60% range. One full uninterrupted discharge-to-shutdown followed by a full charge to 100% resets the coulomb counter reference and brings the percentage reporting back into line.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below what the modem and display load require, even though the fuel gauge is still showing charge remaining. A new Li-ion cell can have a steeper voltage cliff under high-current draw until it has been broken in through a few cycles. The BMS trips to protect the cell before the OS registers a low-battery warning. If this occurs, charge to 100% and repeat two full discharge cycles — by the third cycle the voltage sag under load typically stabilises above the 3.4V cutoff threshold.