T-Mobile Tap HB5A2H Compatible Battery 3.7V 1100mAh

T-Mobile Tap / Pulse Mini — 3.7V Li-ion Replacement Battery (HB5A2H)

This is a 3.7V, 1100mAh Li-ion cell that fits the T-Mobile Tap and Pulse Mini smartphones. It replaces the original HB5A2H or BTR7519 battery when the existing cell can no longer hold a usable charge. Dimensions are 54.05 × 34.10 × 5.40mm — verify these against your current cell before installing.

• Tap and Pulse Mini compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The HB5A2H and BTR7519 part numbers reference the same physical cell form factor, so one replacement covers both devices.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS responded correctly to charge termination at 4.2V and engaged protection cutoff under simulated load at low state-of-charge — no anomalous heat, no swelling.
• Fuel gauge recalibration on first use: On first use after installation, complete one full discharge-to-charge cycle with fast charging disabled. This lets the phone's fuel gauge IC map the new cell's discharge curve before high-current charging runs into an uncalibrated state-of-charge register.

Why the Tap reports wrong battery percentage after a cell swap

The fuel gauge IC in the Tap 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 phone reads voltage and maps it against the old curve, producing percentage figures that are too high or too low. One full discharge and charge cycle — without interruption — forces the IC to relearn the curve against the new cell.

Sudden shutdown at 20–30% charge remaining

This happens when the cell voltage drops below the modem's or display's minimum operating threshold under load, even though the fuel gauge still shows charge remaining. A fresh cell with an uncalibrated fuel gauge IC is especially prone to this — the reported percentage is optimistic relative to actual cell voltage. The fix is the same recalibration cycle: run the battery down to automatic cutoff, then charge uninterrupted to 100%. After one full cycle, the IC adjusts its cutoff estimate and the shutdowns stop.