T-Mobile myTouch 3G Slide 35H00127-02M Replacement Battery 3.7V

T-Mobile myTouch 3G Slide — 3.7V Li-ion Replacement Battery (35H00127-02M)

This 3.7V 1000mAh Li-ion cell is a direct replacement for the T-Mobile myTouch 3G Slide. It fits the 2010-era Android slider with a physical QWERTY keyboard. Cross-references include 35H00127-06M, 35H00127-04M, 35H00127-05M, BA S440, and BB00100.

• myTouch 3G Slide platform fit: All five OEM part numbers above reference the same 3.7V single-cell pack with an identical connector footprint and BMS handshake. HTC manufactured this phone for T-Mobile under a co-branded arrangement, which is why the OEM part pool carries both HTC and T-Mobile part numbers.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a myTouch 3G Slide. The BMS accepted charge without tripping on first insertion, and the protection circuit held cutoff at the correct low-voltage threshold throughout the test cycle.
• Fuel gauge recalibration on first use: On first installation, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before use. The myTouch 3G Slide uses a basic coulomb counter that reads against the original cell's discharge curve — a full cycle rewrites that baseline to match the new cell.

Why the myTouch 3G Slide reports wrong battery percentage after a cell swap

The myTouch 3G Slide tracks charge state using a coulomb counter in the battery circuit, not a sophisticated fuel gauge IC. That counter was calibrated to the original cell's internal resistance and discharge slope. A new cell has different impedance characteristics, so the counter starts reading against the wrong curve immediately after installation. One full discharge-to-shutdown followed by a complete uninterrupted charge resets the counter's reference points and brings percentage reporting back in line.

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

This is a voltage-cliff failure, not a capacity problem. When the modem transmits or the screen backlight spikes, current draw pulls cell voltage down sharply. If the cell voltage drops below roughly 3.0V under that load, the BMS trips and shuts the phone down even though the coulomb counter still shows charge remaining. The fix is to complete the recalibration cycle described above — one full discharge to auto-shutoff, then a full charge. After calibration, the system learns where the real voltage cliff sits and adjusts the low-battery cutoff warning accordingly.