BLU Hero 2 Replacement Battery N4D110J 3.7V 1200mAh

BLU Hero 2 — 3.7V Li-ion Replacement Battery (N4D110J)

This is a 3.7V, 1200mAh Li-ion battery for the BLU Hero 2 smartphone. It replaces the original N4D110J cell when the existing battery degrades, swells, or stops holding a charge. Capacity figures come from the product data: 1200mAh / 4.44Wh.

• Hero 2 platform fit: The Hero 2 uses a fixed 3.7V single-cell architecture with a compact 60.00 × 43.80 × 4.50mm footprint. This replacement matches that form factor and voltage rail exactly, so the charge IC and connector align without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Hero 2 platform. The BMS accepted the new cell without error flags, and the charge IC completed a full cycle to 4.2V cutoff with no thermal interruption.
• Fuel gauge recalibration on first use: Disable fast charging for the first complete discharge-charge cycle after installation. The fuel gauge IC on the Hero 2 is calibrated to the old cell's discharge curve — one full cycle at standard rate lets it relearn the new cell before high-current charging begins.

Why the Hero 2 reports wrong battery percentage after a cell swap

The Hero 2 uses a coulomb-counter-based fuel gauge IC that stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual voltage-to-capacity relationship of the replacement. The OS reads a percentage derived from the old curve, so it shows inflated or deflated numbers. One full discharge-charge cycle at standard current rate forces the IC to rewrite the reference curve against the new cell's actual behaviour.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity defect. Under modem or screen load, the cell voltage drops sharply around 3.5–3.6V before the fuel gauge expects it, and the protection circuit cuts power to prevent under-voltage damage. On a fresh cell that hasn't been calibrated, the gauge doesn't anticipate that drop. Run one complete discharge to automatic cutoff, then charge uninterrupted to 100% — after that cycle, the fuel gauge IC maps the cliff correctly and the shutdowns stop.