Emporia EL550 Replacement Battery BTY26166 3.7V 550mAh

Emporia EL550 — 3.7V Li-ion Replacement Battery (BTY26166)

This 3.7V, 550mAh Li-ion cell is a direct replacement for the Emporia EL550 mobile phone. It slots into the same battery bay as the original BTY26166 and restores power to a phone that no longer holds a charge or fails to boot. Dimensions are 39.40 × 38.90 × 4.36mm — measure your existing cell before ordering if you are unsure.

• EL550 battery bay fit: The EL550 uses a compact removable cell format at 3.7V nominal. This replacement matches the original voltage rail and connector orientation, so the phone's charge IC sees the new cell without a pinout mismatch.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS accepted a standard charge curve without tripping into protection mode, and the cell held voltage within spec across the discharge sweep.
• Fuel gauge recalibration on first use: On first use after installation, run one full discharge down to auto-shutdown, then charge uninterrupted to 100%. This gives the EL550's fuel gauge IC a reference discharge curve for the new cell — skip this step and the percentage readout will drift from the first day.

Why the EL550 reports wrong battery percentage after a cell swap

The EL550's fuel gauge IC stores a learned discharge curve from the original cell. When you fit a new cell, that stored curve no longer matches actual cell behaviour. The gauge reads percentage against old data, so it can show 40% and drop to shutdown moments later. One complete uninterrupted discharge-to-charge cycle overwrites the old curve with data from the new cell. After that cycle, percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

A 550mAh cell at this capacity is operating close to its voltage cliff under modem and screen load. When the EL550 pulls current for a call or display wake, the cell voltage sags sharply — the BMS reads that sag as undervoltage and cuts output before the gauge reaches 0%. This is not a faulty cell; it is the protection circuit doing its job on a high-impedance load spike. Confirm this is the cause by checking that the phone restarts normally after the shutdown — if it does, the BMS tripped, not the cell. Reduce screen brightness and mobile data activity to flatten the load curve.