About this replacement
NEC NEX 2600 / NEX 2610 — 3.6V Ni-MH Replacement Battery
This is a 3.6V, 750mAh Ni-MH replacement battery for the NEC NEX 2600 and NEX 2610 mobile phones. Both handsets share an identical battery bay, connector pitch, and charge termination spec, so one cell covers both models. Capacity is rated at 2.7Wh.
- NEX 2600 and NEX 2610 compatibility: Both models run the same 3.6V Ni-MH chemistry and use the same physical connector and charge termination logic. NEC did not change the battery spec between these two variants, so one replacement cell fits both without any hardware modification.
- Bench tested on actual hardware: We cycled the cell through charge and discharge on the bench and confirmed the charge IC accepted the negative delta-V termination signal correctly. The BMS did not flag a fault condition at end-of-charge, and the cell held voltage within the expected window across the full discharge curve.
- Ni-MH cycle conditioning on first install: Ni-MH cells respond to how the first cycle is handled. Run the phone down to automatic shutdown on the first use, then charge uninterrupted to full before switching it back on. This gives the charge IC a clean reference point for delta-V detection on subsequent cycles and reduces the chance of early termination on future charges.
Why the NEX 2600 reports wrong battery percentage after a cell swap
The NEX 2600's fuel gauge is calibrated against the discharge curve of the original cell. A new Ni-MH cell has a slightly different internal resistance profile, so the gauge reads against the wrong reference from the start. This causes the percentage to jump or stall at points that don't match actual capacity. One full uninterrupted discharge down to auto-shutdown, followed by a complete charge, resets the gauge's reference curve to the new cell.
Sudden shutdown at 20–30% on the NEX 2600 after replacement
This is a voltage cliff issue. Ni-MH cells have a relatively flat discharge curve that drops sharply near depletion — the phone's power management circuit cuts out when voltage falls below its minimum threshold, even though the gauge still shows charge remaining. On a new cell, this happens until the fuel gauge recalibrates to the new discharge curve. After one full conditioning cycle, the gauge aligns better with actual cell voltage and the shutdowns stop. If they persist beyond two full cycles, check that the battery contacts are clean and making firm contact — corroded pins add resistance and accelerate the voltage drop under load.