K-Touch S5 Replacement Battery TBT9701 3.7V 1800mAh

K-Touch S5 / T810 Series — 3.7V Li-ion Replacement Battery (TBT9701)

This is a 3.7V, 1800mAh Li-ion cell replacing the original TBT9701 / TBW9701 battery in K-Touch smartphones. It fits the S5, S5T, T810, and E88, along with six additional K-Touch handsets that share the same battery bay dimensions and connector. Physical size is 72.00 × 56.90 × 4.50mm — verify against your existing cell before ordering.

• S5 / T810 series fit: These models share a common battery footprint, connector pinout, and BMS handshake protocol across the range. One replacement cell covers all listed variants without adapter or modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on K-Touch hardware. The BMS accepted charge from the device's charge IC without tripping overcurrent or overvoltage cutoff, and the cell voltage held stable across a full discharge curve.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging pushes current into an uncalibrated state. Skip this step and percentage readings will drift.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still running the discharge curve from the old, degraded cell. The new cell has a steeper voltage drop under modem and screen load than the old cell did, so the phone hits a voltage floor the IC doesn't recognise as low — until the hardware forces a cutoff. The fix is one full discharge-to-shutdown followed by a full charge with fast charging off. After that cycle, the coulomb counter recalibrates to the new cell's actual curve and the shutdowns stop.

Phone won't power on after the battery sat in storage

Li-ion cells that drop below roughly 2.5V trigger a BMS lockout — the protection circuit opens and blocks current flow entirely. A standard wall charger may not push enough trickle current through the BMS to recover the cell. Connect the phone to a USB power source that delivers a consistent 5V/500mA, leave it connected for 20–30 minutes without pressing the power button, then attempt a cold boot. If the BMS re-initialises, the charge IC will take over and bring the cell up to normal voltage from there.