Nokia BP-3L Replacement Battery 303 3.7V 1000mAh

Nokia 303 / Lumia 710 / Asha 303 — 3.7V Li-ion Replacement Battery (BP-3L)

This is a 3.7V, 1000mAh Li-ion cell built to the BP-3L spec. It fits the Nokia 303, 603, Lumia 710, Asha 303, and several other Nokia handsets that share the same battery bay dimensions and connector. Capacity figures come from the product data — 3.7Wh total energy.

• Multi-model fit — shared battery platform: Nokia used the BP-3L cell across a range of S40, S60, and Windows Phone handsets from roughly 2011–2013. The voltage rail, physical footprint (66.00 × 43.90 × 4.60mm), and connector are identical across the 303, 603, Lumia 710, and Asha 303, so one cell covers all of them.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Nokia 303 and a Lumia 710. The BMS accepted charge from both the original wall adapter and a standard 5V USB source. Cell voltage held steady above 3.5V through the mid-range of discharge before the expected taper toward cutoff.
• Fuel gauge recalibration on first cycle: After fitting this cell, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% before use. The Nokia fuel gauge IC is calibrated to the original cell's discharge curve — skipping this step causes the percentage counter to report inaccurate figures until it relearns the new cell.

Why the Lumia 710 reports wrong battery percentage after a BP-3L swap

The Lumia 710 uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell over time. When you swap cells, the IC still holds the capacity model of the old, degraded battery. A fresh 1000mAh cell has a different discharge curve, so the reported percentage drifts from reality — often reading 15–20% too high or dropping suddenly near the end. One complete discharge-charge cycle forces the IC to reset its capacity model against the actual cell. After that cycle, percentage reporting stabilises.

Sudden shutdown at 20–30% on the Nokia 303

This happens when the cell voltage drops below the modem's minimum rail under transmit load — even though the fuel gauge still shows charge remaining. On the Nokia 303, the GSM radio draws a short, sharp current spike during a call or data burst. A new cell occasionally shows this on its first few cycles because the BMS protection threshold is conservative until the cell is conditioned. If the phone shuts off mid-call with percentage still showing, check the resting voltage — it should recover to at least 3.6V within 60 seconds of shutdown. If it does, run two more full discharge-charge cycles; the shutdowns typically stop once the BMS settles.