T-Mobile myTouch HD BA S470 Replacement Battery 3.7V 1250mAh

T-Mobile myTouch HD / PD98120 — 3.7V Li-ion Replacement Battery (BA S470)

This is a 3.7V, 1250mAh Li-ion replacement battery for the T-Mobile myTouch HD and PD98120 smartphone. It replaces OEM part numbers BA S470, BD26100, 35H00141-02M, 35H00141-03M, and 35H00141-00M. Swap it in when the original cell no longer holds a charge or shuts down unexpectedly under load.

• myTouch HD and PD98120 fitment: Both the myTouch HD and PD98120 share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers both devices without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the myTouch HD platform. The BMS accepted charge current without tripping, voltage held steady through screen-on and modem-active loads, and cutoff triggered cleanly at the low-voltage threshold.
• Fuel gauge recalibration on first use: After installation, run one full discharge to near-empty, then charge to 100% without interruption. The phone's fuel gauge IC is calibrated to the old cell's discharge curve — skipping this cycle causes the percentage counter to read inaccurately for days.

Why the myTouch HD reports wrong battery percentage after a cell swap

The myTouch HD uses a coulomb-counter fuel gauge IC that builds its percentage model from learned discharge curves of the previous cell. A new cell has a different internal resistance and discharge profile, so the IC's stored map no longer matches actual capacity. The phone reads a voltage point on the old curve and reports the wrong number — typically showing full charge while the real state-of-charge is lower. One complete uninterrupted discharge and recharge cycle forces the IC to relearn against the new cell and restore accurate reporting.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or screen draws a burst of current and the cell voltage sags below the BMS cutoff threshold, even though the reported percentage looks safe. On an uncalibrated fuel gauge, the displayed percentage is ahead of the real voltage — the cell hits the 3.0V cutoff before the counter reaches zero. The fix is the same recalibration cycle: drain the phone to auto-shutdown, then charge uninterrupted to 100%. After one full cycle the fuel gauge maps the new cell's voltage cliff correctly and shutdown warnings appear at the right percentage.