About this replacement
T-Mobile Wing — 3.7V Li-Polymer Replacement Battery (35H00078-02M)
This is a 3.7V, 2400mAh Li-Polymer battery for the T-Mobile Wing and Wing US pocket PC smartphone. It replaces OEM part numbers 35H00078-02M and HERA160. When the original cell degrades, the Wing drops off charge fast — this cell restores full capacity to the power rail.
- Wing and Wing US fit: Both variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One part number covers both — no adapter or modification needed.
- Bench tested on actual hardware: We cycled this cell through the Wing's charge controller and confirmed the BMS negotiated correctly, accepted a full charge, and held voltage within spec across load. No false-full cutoff observed.
- Pre-swap sync required: The Wing stores open files, contacts, and application state in volatile RAM powered directly by the main battery. Remove the battery without syncing first and that data is gone. Sync to ActiveSync or Windows Mobile Device Center before you pop the cell.
Why the Wing loses all open data the moment the battery comes out
Windows Mobile devices like the Wing use SRAM for working memory, not flash. SRAM needs continuous power to hold its state — the moment the battery is removed, that memory clears. This affects open documents, unsaved contacts, running application state, and sometimes the Today screen configuration. The Wing has no supercapacitor or backup cell to bridge the gap during a swap, so power removal equals data removal. A full ActiveSync backup before the swap is the only protection.
Wing won't boot after new battery installed
A freshly shipped Li-Polymer cell often arrives below 3.0V after storage in transit. The Wing's boot ROM checks the voltage rail before starting the kernel, and if the cell reads too low, the device simply won't respond to the power button. This is not a fault with the battery or the device. Plug the Wing into its charger and leave it for at least 60 minutes before attempting to power on — the charge controller will bring the cell up from low voltage first, and the device will boot normally once the cell clears approximately 3.4V.