Nokia S5420AP C1 2019 Replacement Battery 3.8V 2300mAh

Nokia C1 2019 / TA-1165 — 3.8V Li-ion Replacement Battery (S5420AP)

This is a 3.8V, 2300mAh Li-ion replacement battery for the Nokia C1 2019 smartphone, including TA-1165 variants. It matches the OEM part number S5420AP and fits the physical footprint of the original cell at 77.00 × 59.90 × 4.20mm. Install it when the original battery no longer holds charge or shuts the phone down unexpectedly.

• C1 2019 and TA-1165 compatibility: Both the C1 2019 and TA-1165 share the same battery bay dimensions, connector pinout, and BMS handshake protocol — a single cell covers the full variant range without modification.
• Bench tested on actual hardware: We cycled this cell through a full discharge-charge sequence on a Nokia C1 2019 unit. The BMS accepted the cell without error flags, charge current ramped correctly into the CV phase, and the fuel gauge IC updated state-of-charge readings as expected.
• First-cycle calibration on the C1 2019: Disable fast charging for the first complete discharge-charge cycle after installation. The Nokia C1 2019's fuel gauge IC is calibrated against the original cell's discharge curve. Letting a full slow cycle run first gives the coulomb counter an accurate baseline before high-current charging begins.

Why the Nokia C1 2019 reports wrong battery percentage after a cell swap

The C1 2019 uses a coulomb-counter-based fuel gauge IC that builds its charge model from the original cell's voltage-versus-capacity curve. When a new cell goes in, that stored curve no longer matches the actual cell chemistry, so the IC reports percentages based on stale data. The mismatch is worst in the mid-range — the phone may show 50% while the actual cell voltage is already below 3.6V. One full slow discharge to automatic shutdown followed by an uninterrupted charge to 100% lets the IC remap to the new cell. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on a freshly installed cell

This is a voltage-cliff problem, not a defective cell. Under peak modem or screen load, the cell briefly drops below the BMS cutoff threshold — typically around 3.2V — even though the displayed percentage suggests charge remains. The fuel gauge IC hasn't recalibrated yet, so it reports remaining capacity that the cell can't actually sustain under load. Run one full discharge-charge cycle at standard charge speed. If shutdowns persist after calibration, check that the battery connector is fully seated — a partial connection increases contact resistance and worsens voltage sag under load, dropping the cell voltage below the 3.2V cutoff faster.