Telstra E700 F860 F868 Li-ion Replacement Battery 3.7V 1200mAh

Telstra E700 / F860 / F868 / F866 — 3.7V Li-ion Replacement Battery (Li3712T42P3h633959)

This 3.7V 1200mAh Li-ion battery replaces the original cell in the Telstra E700, F860, F868, F866, and I909 handsets. It matches the OEM part number Li3712T42P3h633959 and fits the original battery bay without modification. Voltage and capacity are 3.7V and 1200mAh (4.44Wh) — use these figures when comparing against your old cell.

• E700 / F860 / F868 / F866 / I909 compatibility: These five models share the same battery footprint, connector pinout, and BMS handshake protocol. One cell works across all of them because the charge IC on each device reads the same identification line from the Li3712T42P3h633959 pack.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on representative hardware in this family. The BMS accepted the charge IC handshake cleanly, held cutoff at 4.2V on charge termination, and triggered low-voltage protection at the correct floor without fault flags.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle before normal use. The fuel gauge IC on these handsets is calibrated against the old cell's discharge curve — a full cycle lets the coulomb counter re-anchor to the new cell before high-current charging is applied.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC still holds the discharge curve of the degraded original cell. When screen brightness peaks or the modem transmits at full power, current draw spikes and the new cell's actual terminal voltage drops faster than the OS expects. The device interprets this as a hard undervoltage and shuts down — even though the coulomb counter still shows charge remaining. One full discharge cycle to ~3.3V under normal load, followed by a full charge, forces the IC to rebuild its curve against the new cell chemistry.

Phone warm near the battery compartment on the first charge cycle

A fresh high-impedance cell generates more heat during the first charge than a broken-in one. The charge IC pushes current into a cell with higher internal resistance than the worn original, which converts more energy to heat before the resistance drops over the first few cycles. This is normal and typically resolves by the third full charge cycle. If the handset stays warm beyond that point, check that the charge rate has not defaulted to a fast-charge profile — drop it to standard 5V/1A for the break-in period.