About this replacement
Mobistel Cynus T1 — 3.7V Li-ion Replacement Battery (BTY26179)
This is a 3.7V, 1980mAh Li-ion replacement battery for the Mobistel Cynus T1 smartphone. It replaces OEM part BTY26179 and fits the Cynus T1 directly. Use this when the original cell has degraded, won't hold charge, or has failed outright.
- Cynus T1 fitment: The Cynus T1 uses a removable 3.7V single-cell Li-ion pack with a fixed connector pinout and BMS handshake matched to the phone's charge IC. This replacement matches that connector, cell voltage, and BMS communication so the device recognises the pack on first boot.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS cutoff at the low end and charge termination at 4.2V. The protection circuit triggered correctly at both ends with no false trips under steady load.
- Fuel gauge recalibration on first use: On first installation, disable fast charging and run one full discharge-charge cycle before normal use. This lets the Cynus T1's fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the Cynus T1 after a cell swap
This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load that the gauge didn't predict, so the phone shuts down before the reported percentage reaches zero. It is not a defective battery. Run one full discharge to automatic shutdown, then charge uninterrupted to 100% — the fuel gauge IC recalibrates against the new cell during that cycle and the premature cutoff stops.
Phone won't power on after the BTY26179 sat in storage
Li-ion cells in storage self-discharge slowly. If the cell drops below approximately 2.5V, the BMS enters lockout to prevent damage to the cell chemistry. The Cynus T1 will show nothing on screen — no charging animation, no boot logo. Connect the phone to a wall charger rated at 5V/1A and leave it for 20–30 minutes without pressing any buttons. Once the BMS sees enough voltage to exit lockout, the charging indicator will appear and the phone will boot normally.