UMI Emax Li3834t43p6h886740 Compatible Battery 3.8V 3300mAh

UMI Emax / Hierro / Super — 3.8V Li-Polymer Replacement Battery (Li3834t43p6h886740)

This is a 3.8V, 3300mAh lithium-polymer cell that replaces part number Li3834t43p6h886740 in the UMI Emax, Hierro, and Super smartphones. It matches the original cell's voltage, physical dimensions (87.34 × 65.42 × 3.80mm), and connector layout. Capacity is 3300mAh — 12.54Wh total energy.

• Emax, Hierro, and Super compatibility: These three UMI models share the same battery bay geometry, connector pinout, and BMS handshake protocol. One cell covers all three — no hardware modification needed.
• Bench tested on actual hardware: We cycled this cell through charge, load, and cutoff on the Emax platform. The BMS accepted the cell without triggering a rejection flag, and charge termination fired correctly at 4.35V.
• Fuel gauge recalibration on first cycle: After fitting this cell, disable fast charging and run one full discharge-to-charge cycle at standard rate. The fuel gauge IC on these UMI models learns the new cell's discharge curve during that first cycle — skipping it leaves the coulomb counter calibrated to the old, degraded cell.

Why the UMI Emax reports wrong battery percentage after a cell swap

The fuel gauge IC on the Emax stores a learned discharge curve from the original cell. When you install a fresh 3300mAh cell, that stored curve no longer matches actual cell behaviour. The gauge reads voltage and compares it against the old model, so it reports percentage values that are off — sometimes by 15–20%. One full standard-rate discharge-charge cycle rewrites the reference curve and brings the display back into alignment.

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

This is a voltage cliff event — not a capacity fault. Under heavy load (modem handoff, screen at full brightness, or background sync), the cell's terminal voltage drops faster than the fuel gauge expects from the old discharge model. The system hits the hardware undervoltage threshold before the percentage counter reaches zero and shuts down immediately. Let the phone sit powered off for two minutes after shutdown, then charge to 100% without interruption. After two full cycles, the gauge model updates and the cliff shifts back below 10%.