Nokia BP-5L 7710 Replacement Battery 3.7V 1300mAh

Nokia 7710 / 770 Series — 3.7V Li-ion Replacement Battery (BP-5L)

The BP-5L is a 3.7V, 1300mAh Li-ion cell that fits the Nokia 7710, 770, 7700, and 9500 among other compatible handsets. These mid-2000s Nokia devices share the same battery bay dimensions and connector, so one cell covers the full BP-5L family. This listing is for users whose original cell no longer holds charge through a normal day of use.

• BP-5L platform compatibility: Nokia used the BP-5L across several devices that share the same 65.80 × 43.80 × 5.30mm footprint, voltage rail, and connector pinout. The BMS handshake requirements are identical across the 7710, 770, 7700, and 9500, so the cell slots in without adapter or firmware conflict.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a 7710 unit and confirmed the BMS accepted the cell on first insertion, raised no fault flags, and held voltage above 3.5V through the discharge curve without premature cutoff.
• Fuel gauge recalibration on first use: On the first cycle after installation, run the battery down to automatic shutdown and charge it back to 100% without interruption. The Nokia fuel gauge IC maps its calibration table to the new cell's discharge curve during this first full cycle — skipping it causes erratic percentage readings from day one.

Sudden shutdown at 20–30% on the 7710 after a cell swap

This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The old cell had a steeper voltage drop at low charge, so the IC expects the same profile. When the new cell hits a load spike — screen at full brightness or a data burst — the IC reads the voltage dip as a hard cutoff threshold and kills the device. The fix is one full uninterrupted discharge cycle down to automatic shutdown, followed by a full charge. After that single cycle the coulomb counter resets against the new cell and the phantom cutoffs stop.

Nokia 7710 showing wrong battery percentage after replacement

The Nokia 7710 stores fuel gauge calibration data tied to the previous cell's internal resistance and capacity curve. A fresh BP-5L has lower internal resistance than a degraded original, so the IC over-reports or under-reports state of charge until it gathers new data. You may see the percentage jump several points up or down without any load change. Charge to 100%, use the device until it shuts off automatically, then charge back to 100% without interruption — after this single cycle the IC recalibrates and percentage readings stabilise.