SVP Nokia Tango C4D10T Replacement Battery 3.7V 1200mAh

SVP Nokia Tango / Deco Pro — 3.7V Li-ion Replacement Battery (C4D10T)

This SVP X-Longer battery replaces the original cell in the Nokia Tango and Deco Pro smartphones. It runs at 3.7V with a 1200mAh (4.44Wh) capacity, matching the stock specification. Dimensions are 60.00 × 43.80 × 4.50mm — a direct physical match for the original battery bay.

• Tango and Deco Pro compatibility: Both models share the same battery bay dimensions, connector pinout, and charge IC communication protocol, which is why one cell covers both handsets. The BMS in each phone reads charge state over the same two data lines.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes on the Nokia Tango. The BMS handshake completed correctly, charge termination triggered at the expected voltage ceiling, and the protection circuit tripped at the rated low-voltage cutoff.
• Fuel gauge recalibration on first install: After fitting this cell, disable fast charging and complete one full discharge-to-charge cycle before normal use. This gives the fuel gauge IC time to map the new cell's discharge curve — skipping this step is the main reason percentage readings jump erratically in the first few days.

Why the Tango reports wrong battery percentage after a cell swap

The Nokia Tango uses a coulomb-counter-based fuel gauge IC that builds a discharge model over time. When you swap in a new cell, the IC still references the old cell's learned curve. Until the IC recalibrates, the displayed percentage can read 10–15 points higher or lower than actual charge state. One complete discharge from 100% down to auto-off, followed by a full uninterrupted charge, resets the learned curve to the new cell's actual behaviour.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or screen pulls peak current and the cell voltage drops sharply — the BMS reads this as a low-voltage fault and cuts power, even though the reported percentage still looked safe. It is a calibration gap, not a faulty cell. The fuel gauge IC flagged 25% remaining, but the actual resting voltage under load was already near the 3.0V cutoff threshold. Run one full cycle as described above and the gauge will align its percentage readings to the real voltage curve.