About this replacement
NEC N100 / N108 / N109 / N3301 Series — 3.7V Li-ion Replacement Battery
This 3.7V, 650mAh Li-ion cell replaces the original battery in the NEC N100, N108, N109, and N3301 smartphones. It fits the full compatible model range listed above. Voltage and capacity match factory spec so the phone's charge IC accepts the new cell without modification.
- N100 / N108 / N109 / N3301 fit group: These models share the same battery bay dimensions, connector pinout, and 3.7V nominal voltage rail. The BMS handshake expectation is identical across the group, so one cell covers all four platforms without rewiring or adaptation.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on compatible NEC hardware. The BMS accepted the cell on first connection, charge termination triggered correctly at 4.2V, and protection circuitry tripped as expected on a simulated deep-discharge event below 2.5V.
- Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if supported, then run one full discharge down to automatic cutoff followed by a complete charge to 100%. This gives the fuel gauge IC one clean cycle to map the new cell's discharge curve before reporting accurate percentages.
Why the NEC N100 reports wrong battery percentage after a cell swap
The phone's fuel gauge IC stores a learned discharge curve from the original cell. When a new cell goes in, that stored curve no longer matches the actual electrochemistry. The gauge reads voltage and translates it to a percentage using old data, so it can be off by 10–20% until it relearns. One full discharge-to-cutoff and charge-to-100% cycle resets the coulomb counter and forces the IC to rebuild its reference map against the new cell.
Sudden shutdown at 20–30% remaining on the replacement cell
This happens when the cell voltage drops sharply under load — a voltage cliff — faster than the fuel gauge predicted from its stored curve. The modem or screen draws a brief current spike, cell voltage dips below the BMS cutoff threshold, and the phone shuts off even though the percentage display still showed charge remaining. It is most common in the first few cycles after a swap, before the gauge has recalibrated. Run one complete discharge cycle without interruption; the shutdowns typically stop once the fuel gauge IC has accurate low-voltage data for the new cell, usually confirmed by reaching a stable 3.4V under moderate load near the 10% mark.