Neffos N1 Replacement Battery NBL-35A3200 3.85V 3000mAh

Neffos N1 / TP908A — 3.85V Li-Polymer Replacement Battery (NBL-35A3200)

This is a 3.85V, 3000mAh lithium-polymer cell built to the NBL-35A3200 specification for the Neffos N1 and TP908A smartphones. It replaces the original pouch cell when the phone no longer holds charge or shuts down unexpectedly. Capacity is rated at 11.55Wh and dimensions match the original bay at 84.14 × 63.80 × 3.62mm.

• N1 and TP908A platform fit: Both models share the same mainboard layout, connector pinout, and charge IC — the NBL-35A3200 cell interfaces directly with the same BMS handshake on either device without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and controlled discharge passes on the N1 platform and confirmed the BMS accepted the cell, reported state-of-charge correctly, and held voltage above the cutoff threshold under sustained screen and modem load.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle at standard current. This lets the fuel gauge IC map its coulomb counter to the new cell's actual discharge curve before high-current charging begins on an uncalibrated reference.

Sudden shutdown at 20–30% on the Neffos N1 after a cell swap

The N1's fuel gauge IC holds a discharge model from the previous cell. When the curve stored in the coulomb counter doesn't match the new cell's actual voltage-versus-capacity relationship, the IC misreads remaining charge. Under modem transmit or display load, the cell voltage dips sharply at the real empty point — often 3.5–3.6V — while the gauge still shows 20–30%. The phone's low-voltage protection trips and cuts power before the OS can warn the user. One full slow discharge-recharge cycle forces the IC to relearn the curve and eliminates most unexpected shutoffs.

USB fast charge not activating on the first cycle after replacement

After a cell swap, the charge IC on the N1 may default to trickle or standard 5V charging on the first cycle rather than negotiating fast-charge protocol. This happens because the IC detects an uncalibrated cell and applies a conservative current limit as a precaution. It is not a fault with the replacement cell or the charger. Complete one standard-rate charge cycle first — the IC will accept full fast-charge negotiation from the second cycle onward.