About this replacement
E-TEN glofiish M700 — 3.7V Li-Polymer Replacement Battery (49004440_X500)
This 3.7V, 2400mAh lithium-polymer cell is a direct swap for the original battery in the E-TEN glofiish M700 smartphone. The M700 is a Windows Mobile PDA-phone from the mid-2000s that runs GPS, cellular, and Wi-Fi simultaneously — a load profile that accelerates original cell degradation. Capacity listed here is 8.88Wh as sourced from product data.
- glofiish M700 fit: The M700 uses a slim Li-Polymer cell with a three-pin connector that routes both charge current and fuel gauge data through the same flex strip. The BMS in this replacement matches that pinout and charge termination voltage, so the charge IC on the motherboard recognises the cell without throwing a fault.
- Bench tested on actual hardware: We cycled this cell through the M700's charge IC and confirmed the BMS holds the charge rail at 4.2V at termination. The protection circuit tripped correctly on a simulated short and recovered cleanly when the fault was cleared.
- First-cycle fuel gauge recalibration: On first use after installation, disable any sync or background data push and run one full discharge down to automatic shutoff, then charge uninterrupted to 100%. The M700's fuel gauge IC was calibrated to the old cell's discharge curve — one complete cycle resets the coulomb counter against the new cell's actual capacity.
Why the glofiish M700 reports the wrong battery percentage after a cell swap
The M700 uses a coulomb-counting fuel gauge IC that builds a discharge model over repeated cycles. When you replace the cell, the IC still holds the old cell's learned capacity curve in memory. Until it observes a full discharge-to-shutoff followed by a complete charge cycle on the new cell, the percentage readout is interpolating against stale data. After one full cycle, the IC recalibrates and the reported percentage will track accurately against real remaining capacity.
Sudden shutdown at 20–30% on the glofiish M700
This is a voltage cliff, not a capacity problem. When the M700 activates the cellular radio or GPS alongside the screen backlight, instantaneous current draw spikes and the cell voltage drops sharply. If the fuel gauge still thinks 30% remains but the cell can no longer hold voltage above the BMS cutoff threshold under that load, the BMS trips and the phone shuts off. Run one complete discharge-charge cycle to let the fuel gauge IC map the new cell's actual voltage-versus-capacity curve. After calibration, the phone will call the low-battery warning at a voltage level that reflects real usable capacity — typically around 3.6V under load.