Evolveo EasyPhone EP-500 Replacement Battery 3.7V 1200mAh

Evolveo EasyPhone EP-500 — 3.7V Li-ion Replacement Battery (EP-500)

This is a 3.7V, 1200mAh Li-ion cell for the Evolveo EasyPhone EP-500 — a compact feature-adjacent phone built for calls and messaging. It replaces the original battery when capacity has faded or the cell no longer holds charge. Dimensions are 53.00 × 33.90 × 5.70mm, matching the original battery bay.

• EasyPhone EP-500 fitment: The EP-500 uses a removable battery with a fixed connector orientation and a shallow bay depth of 5.70mm. This cell matches that physical envelope and the 3.7V nominal rail the phone's charge IC expects.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the EP-500 platform. The BMS held cutoff correctly at both ends — no false-full stops and no undervoltage lockout during normal discharge.
• First-cycle fuel gauge reset: After installing a new cell, run one complete discharge down to automatic shutdown and then charge uninterrupted to 100% before using the phone normally. This gives the fuel gauge IC a clean reference curve for the new cell's actual capacity.

Why the EP-500 reports wrong battery percentage after a cell swap

The EP-500 uses a fuel gauge IC that builds its charge estimates from the discharge curve of the previous cell. When you fit a new cell, the IC still references the old curve until it sees one full cycle. Until then, the displayed percentage drifts — often reading 15–20% higher than actual charge state. One complete discharge-to-shutdown followed by a full uninterrupted charge resets the coulomb counter and aligns the gauge to the new cell's actual 1200mAh curve.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — typically when the modem transmits or the screen backlight peaks — pulling the cell below the BMS cutoff threshold even though the gauge still shows charge remaining. It is a voltage-cliff failure: the cell cannot sustain the required voltage under instantaneous current demand. A fresh cell out of storage may sit near this cliff if it has partially self-discharged. Charge the battery fully to 4.2V before first use and run the fuel gauge calibration cycle to push the shutdown point back to the correct low-voltage floor.