Elson ESL808 Replacement Battery BTY26152 3.7V 700mAh

Elson ESL808 — 3.7V Li-ion Replacement Battery (BTY26152)

This is a 3.7V, 700mAh Li-ion battery for the Elson ESL808 smartphone. It replaces the original BTY26152 cell when the existing battery no longer holds a charge or has failed entirely. Dimensions are 52.28 × 40.37 × 5.84mm — confirm these against your original before fitting.

• ESL808 cell fitment: The ESL808 uses a single-cell Li-ion pack at 3.7V nominal. This replacement matches that voltage rail and the physical connector layout the device expects. No adaptation needed at the board level.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS held cutoff correctly at both the low-voltage floor and full-charge ceiling, with no thermal events during the charge phase.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Why the ESL808 reports wrong battery percentage after a cell swap

The ESL808's fuel gauge IC builds its percentage model from the old cell's discharge curve stored in memory. When you fit a new cell, that curve no longer matches the actual chemistry, so the reported percentage drifts — often reading higher than reality. The fix is one full discharge-charge cycle with fast charging off. After that single cycle, the coulomb counter recalibrates against the new cell and percentage readings stabilise.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load — modem transmit bursts or screen backlight spikes pull current the battery cannot sustain at that state of charge. The BMS sees voltage collapse below its cutoff threshold and shuts the device down before the OS can register the drop. It is not a faulty cell — it is the fuel gauge IC still using the old cell's voltage-to-percentage map. Run one full calibration cycle and the shutdown threshold will shift to the correct low-percentage range. After calibration, the device should reach below 5% before any unexpected cutoff.