WIZA16 T-Mobile MDA Vario Replacement Battery 3.7V 2800mAh

T-Mobile MDA Vario — 3.7V Li-ion Replacement Battery (WIZA16)

This is a 3.7V, 2800mAh Li-ion battery for the T-Mobile MDA Vario, MDA Usm, and MDA IV 4. All three devices share the WIZA16 form factor, connector, and BMS handshake. Swap it in when the original cell can no longer hold a usable charge across a full day.

• MDA Vario, MDA Usm, MDA IV 4 compatibility: These Windows Mobile devices run the same hardware platform and use an identical battery bay, connector pin-out, and BMS communication protocol — one cell fits all three without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the MDA platform. The BMS accepted the new cell without error flags, and charge IC handshake completed normally on the first cycle.
• Fuel gauge recalibration on first use: After installation, run one complete discharge-charge cycle before enabling any fast charge or sync-heavy tasks. The fuel gauge IC on these devices calibrated itself to the original cell's discharge curve — a full cycle against the new cell resets that baseline so percentage readings stay accurate.

Sudden shutdown at 20–30% on the MDA Vario after a cell swap

The MDA Vario's processor and cellular radio draw short, sharp current spikes — particularly during screen wake and data sync. A new cell with a slightly different internal resistance curve can hit a voltage floor under that load even when the fuel gauge still reads 20–30%. The BMS reads this as a low-voltage event and cuts power before the percentage reaches zero. One full discharge-charge cycle lets the coulomb counter re-map the new cell's actual capacity and voltage curve, and the premature shutdowns typically stop after that.

Device won't power on after the battery sat in storage

Li-ion cells self-discharge in storage, and if a battery drops below 2.5V per cell the BMS enters a protection lockout — it blocks current flow entirely to prevent cell damage. The MDA Vario won't respond to the power button in this state; it looks completely dead. Connect the device to a wall charger and leave it for 15–20 minutes without pressing anything — the charge IC trickle-charges the cell back above the lockout threshold, and the BMS re-initialises. If the device still shows no sign of life after 30 minutes on charge, check that the charger is delivering at least 5V before swapping anything else.