Mobistel Cynus E7 Replacement Battery 3.8V 2200mAh Li-Polymer

Mobistel Cynus E7 — 3.8V Li-Polymer Replacement Battery

This 3.8V, 2200mAh Li-Polymer cell is a direct replacement for the Mobistel Cynus E7 smartphone. It fits the Cynus E7 only — do not assume cross-compatibility with adjacent Cynus models. Capacity is rated at 8.36Wh under controlled discharge.

• Cynus E7 fit: The E7 uses a specific pouch cell footprint — 74.25 x 60.87 x 4.44mm. That dimensional spec matters because the battery door on this handset clamps against the cell face. A cell even 0.2mm thicker will bow the cover and stress the contact pads.
• Bench tested on actual hardware: We cycled this cell through full charge and load discharge on the Cynus E7 platform. The BMS accepted charge termination correctly and showed no false-full cutoff on the first cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before any high-current session pushes charge into an uncalibrated state.

Why the Cynus E7 reports wrong battery percentage after a cell swap

The Cynus E7 uses a fuel gauge IC that builds its state-of-charge model from the discharge history of the original cell. When a new cell goes in, that learned curve no longer matches the new cell's actual voltage-to-capacity relationship. The gauge will report percentages that drift — sometimes reading 40% when the cell is closer to 15%. One full slow discharge-to-cutoff followed by a full charge resets the coulomb counter and lets the IC rebuild its curve against the new cell.

Sudden shutdown at 20–30% remaining on the Cynus E7

This is a voltage cliff issue, not a capacity issue. Under modem transmit load or screen-on draw, the cell voltage drops faster than the fuel gauge predicted — it hits the BMS low-voltage cutoff while the display still shows 20–30%. It happens most often when the gauge IC has not yet recalibrated to the new cell. Run the recalibration cycle first. If shutdowns continue after two full cycles, check that the resting open-circuit voltage reads at least 3.7V before loading the device.