Nokia BP-4L E90 Replacement Battery 3.7V 1700mAh

Nokia E90 / E71 / E61i Series — 3.7V Li-ion 1700mAh Replacement Battery (BP-4L)

This is a 3.7V Li-ion replacement battery for the Nokia BP-4L cell used across the E90 Communicator, E71, E61i, and related business devices. Capacity is 1700mAh (6.29Wh), matching the original specification. It fits any device in this family that takes the BP-4L form factor.

• E90 / E71 / E61i platform fit: These models share the same BP-4L footprint, connector pinout, and BMS communication protocol. Nokia standardised across this business series so one cell works across the lineup without modification.
• Bench tested on actual hardware: We ran this cell on an E90 Communicator and confirmed the BMS handshake completed correctly on first insertion. The charge IC accepted the cell without rejecting it as unknown, and voltage held steady under simultaneous Wi-Fi and display load.
• Fuel gauge recalibration on first use: After installing this cell, run one full discharge to auto-shutdown, then charge uninterrupted to 100% before normal use. The E90's coulomb counter was calibrated to your old degraded cell — skipping this step causes the percentage display to read inaccurately from day one.

Why the E90 Communicator reports wrong battery percentage after a cell swap

The E90 uses a coulomb counter inside the phone to track charge state. That counter builds a model of the cell's discharge curve over many cycles. When you install a fresh 1700mAh cell, the counter is still using the curve from the worn-out original — so it miscalculates remaining charge. The phone may show 40% remaining and then drop to 10% within minutes. One full discharge-to-shutdown followed by a complete charge resets the reference curve the counter uses.

Sudden shutdown at 20–30% on the BP-4L replacement

This happens when the phone's modem and display draw simultaneous current and the cell voltage sags below the BMS cutoff threshold — even though the fuel gauge still shows charge remaining. It is a voltage cliff, not a capacity problem. A freshly installed cell with an uncalibrated coulomb counter cannot predict the sag point accurately. After one full recalibration cycle, the BMS cutoff and the gauge reading align, and unexpected shutdowns stop. If they continue after two full cycles, check that resting voltage measures 3.7V or above with a multimeter before reinserting.