Manta 4091S Replacement Battery 3.7V 1000mAh Li-ion

Manta 4091S / 4091S Dual SIM — 3.7V Li-ion Replacement Battery (TEL4091S)

This is a 3.7V, 1000mAh Li-ion cell that replaces part number TEL4091S in the Manta 4091S and 4091S Dual SIM smartphones. It fits both single and dual-SIM variants, which share the same battery bay dimensions and connector pinout. Capacity matches the original spec at 3.7Wh.

• 4091S and 4091S Dual SIM compatibility: Both handset variants run the same voltage rail and use an identical physical connector with the same BMS handshake protocol. The cell dimensions — 62 × 38 × 4.50mm — match the original battery bay exactly, so no modification is needed to fit either variant.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on a Manta 4091S unit. The BMS accepted the new cell without fault codes, charge termination triggered correctly at 4.2V, and low-voltage cutoff held at the expected threshold without tripping prematurely under load.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if your handset supports it and run one complete discharge-charge cycle before normal use. This gives the fuel gauge IC time to map the new cell's discharge curve — without it, the percentage readout can drift by 15–20% until calibration catches up.

Why the Manta 4091S reports the wrong battery percentage after a cell swap

The fuel gauge IC on the 4091S uses a coulomb counter that was calibrated against the original cell's internal resistance and discharge curve. When a new cell goes in, that stored calibration no longer matches the actual cell chemistry. The gauge reads a voltage point and maps it to a percentage using old data, so it can appear 30% full when the cell is nearly flat — or vice versa. One full discharge down to automatic shutdown, followed by an uninterrupted charge to 100%, resets the coulomb counter against the new cell's real parameters.

Sudden shutdown at 20–25% with the replacement cell installed

This happens when the modem or display draws a surge of current and the cell voltage drops faster than the gauge expects — the phone hits the hardware undervoltage cutoff before the OS percentage reaches zero. It is a calibration issue, not a faulty cell. The BMS is cutting power at the correct voltage; the percentage shown is simply wrong because the fuel gauge has not yet mapped the new cell's voltage-to-capacity curve. Run the phone down to shutdown once, charge it fully without interruption, and the gauge will recalibrate — shutdown should then align with a reading below 5%.