BLU Bar Q N5B80T Compatible Battery 3.7V 900mAh Li-ion

BLU Bar Q — 3.7V Li-ion Replacement Battery (N5B80T)

This is a 3.7V, 900mAh Li-ion replacement battery for the BLU Bar Q mobile phone. It carries OEM part number N5B80T and fits the Bar Q directly. Install it when the original cell no longer holds a charge through a normal day of calls and messaging.

• Bar Q compatibility: The Bar Q uses a low-voltage 3.7V single-cell pack with a specific connector pitch and BMS handshake tied to the N5B80T part. Swapping to any other cell risks a BMS rejection at the charge IC, preventing the phone from accepting current at all.
• Bench tested on actual hardware: We ran the N5B80T through charge cycles on a Bar Q unit and monitored BMS communication throughout. The protection circuit engaged correctly at both low-voltage cutoff and over-current thresholds. No false rejection from the phone's charge IC was observed.
• Fuel gauge recalibration on first install: On first use after fitting this cell, disable any fast-charging mode and complete one full discharge-charge cycle. The fuel gauge IC on the Bar Q is still calibrated to the old cell's discharge curve. Running one uninterrupted cycle lets the coulomb counter reset against the new cell before reporting accurate percentages.

Why the Bar Q reports wrong battery percentage after a cell swap

The Bar Q uses a fuel gauge IC that builds its charge model from the previous cell's discharge curve. When a new cell goes in, that stored curve no longer matches the actual chemistry. The IC will over- or under-report state of charge until it has seen at least one complete cycle from 100% down to auto-shutoff and back to full. After that cycle, the percentage readout stabilises against the new cell's actual capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC still holds the old cell's voltage-to-capacity map and the new cell hits a steeper voltage cliff under load. When the modem fires during a call or data burst, current draw spikes and cell voltage drops sharply — faster than the IC predicts. The phone's hardware protection reads that as an imminent under-voltage event and cuts power before the display shows 0%. Complete one full discharge cycle to let the coulomb counter recalibrate, and target a resting cell voltage of around 3.85V before the next full charge.