Telstra C88 Li3708T42P3h Compatible Battery 3.7V 800mAh

Telstra C88 / C78 / C70 — 3.7V Li-ion Replacement Battery (Li3708T42P3h553447)

This is a 3.7V, 800mAh Li-ion cell that replaces the original battery in the Telstra C88, C78, C70, and E520 mobile phones. It matches the OEM footprint at 54.29 × 33.71 × 4.43mm, so the connector seats without modification. Capacity is 800mAh — use the original charger and cable throughout.

• C88 / C78 / C70 / E520 platform fit: These models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The BMS handshake is consistent across the range, so one cell covers all listed variants without adapter or wiring change.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the C88 platform. The BMS accepted charge from the first cycle, held low-voltage cutoff correctly at the bottom of discharge, and did not trigger false overcharge flags at 4.2V termination.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging if available and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before the OS starts reporting percentage — skipping this step is the primary cause of erratic percentage readings post-swap.

Why the C88 reports wrong battery percentage after a cell swap

The C88 uses a fuel gauge IC that builds its state-of-charge model from accumulated charge and discharge data — a coulomb counter tied to the original cell's internal resistance profile. When a new cell goes in, that stored model no longer matches the actual discharge curve. The phone reads voltage and translates it to percentage using the old data, which produces readings that are too high, too low, or unstable. One full uninterrupted discharge-then-charge cycle resets the counter and lets the IC relearn the new cell's curve. After that cycle, percentage accuracy returns to normal.

Sudden shutdown at 20–30% remaining on the replacement cell

This is a voltage cliff issue, not a capacity defect. At 20–30% state-of-charge, the cell voltage drops fast under the combined load of the modem radio, screen backlight, and background processes. If the fuel gauge IC hasn't recalibrated yet, it misreads remaining capacity and the phone hits the hardware undervoltage cutoff before the percentage display reaches zero. The fix is that same first-cycle recalibration — one full discharge to shutdown, then a full charge to 100% without interruption. If shutdowns continue after two full cycles, check that the battery connector is fully seated; a loose pin creates resistance that amplifies the voltage sag under load.