Mobistel Cynus T8 Replacement Battery 3.8V 2000mAh

Mobistel Cynus T8 — 3.8V Li-ion Replacement Battery (BTY26190)

This is a 3.8V, 2000mAh Li-ion replacement battery for the Mobistel Cynus T8 smartphone. It slots into the original battery bay and restores power to calls, messaging, and apps. Dimensions are 72.05 × 57.01 × 4.35mm — check these against your compartment before installing.

• Cynus T8 fit: This cell matches the BTY26190 OEM part number and the same connector pinout and voltage rail the Cynus T8 power management IC expects. No modification needed at the hardware level.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a smartphone test rig. The BMS accepted a standard charge handshake without rejecting current or tripping an overvoltage fault.
• Fuel gauge recalibration after install: On first use after swapping this cell in, disable fast charging and run one full discharge-to-charge cycle. The fuel gauge IC on the Cynus T8 is calibrated to the old cell's discharge curve — one slow cycle lets it reset its coulomb counter against the new cell before high-current charging begins.

Sudden shutdown at 20–30% on the Cynus T8 after a cell swap

This is a voltage cliff problem, not a capacity problem. The Cynus T8's modem and display draw enough current during peak load that a new, uncalibrated cell can't sustain voltage above the shutdown threshold — even when the fuel gauge still reads 25%. The power management IC cuts the rail to protect the cell. Running one full slow discharge cycle allows the fuel gauge IC to map the new cell's actual voltage curve and stop triggering early cutoffs.

Cynus T8 not powering on after the replacement battery sat in storage

Li-ion cells self-discharge over time, and if the replacement battery dropped below 2.5V per cell during storage, the BMS will have entered lockout mode to prevent damage. The phone won't power on and may not respond to a charger at all. Connect the phone to a wall charger — not a USB port — and leave it for 20 to 30 minutes without pressing the power button. If the BMS recovers, the phone will show a low-battery screen; from there, charge to at least 3.6V before booting.