About this replacement
T-Mobile MDA Compact V — 3.7V Li-ion Replacement Battery (TOPA160)
This is a 3.7V, 2200mAh Li-ion cell that replaces the original battery in the T-Mobile MDA Compact V. The MDA Compact V is a Windows Mobile PDA and pocket PC from the mid-2000s. It fits units cross-referencing OEM part numbers TOPA160, 35H00125-07M, and BA S360.
- MDA Compact V platform fit: All three OEM part numbers — TOPA160, 35H00125-07M, and BA S360 — share the same 3.7V rail, connector footprint, and BMS handshake protocol on this device. One cell covers all three references.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the MDA Compact V platform. The BMS correctly negotiated with the device, accepted a full charge without fault codes, and held voltage within spec across the full discharge curve.
- RAM state before removal: Sync all open data to a host computer before pulling the old battery. The MDA Compact V holds application state and open files in SRAM powered directly by the main cell — cut power without syncing and that data is gone.
Why the MDA Compact V loses settings after a battery swap
This device stores active application data and user settings in volatile SRAM. That memory requires continuous battery voltage to retain its contents — there is no backup cell. The moment the main battery is removed, the SRAM loses power and all unsaved state is wiped. A full ActiveSync or Windows Mobile Device Center sync to a PC before the swap preserves everything that would otherwise be lost.
MDA Compact V won't boot after new battery installed
A freshly shipped Li-ion cell typically arrives at 30–50% charge — enough for shipping compliance, not always enough to clear the device's minimum boot voltage threshold. If the MDA Compact V shows nothing on screen or loops at the boot logo, the cell is likely below the threshold the BMS requires before it allows the boot sequence to proceed. Connect the device to a charger for at least 30 minutes before attempting to power on. Once the cell reaches approximately 3.6V, the boot sequence should complete normally.