Билайн E300 Replacement Battery 3.7V 700mAh Li-ion

Билайн E300 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 700mAh (2.59Wh) lithium-ion cell for the Билайн E300 mobile phone. It replaces the original battery when the phone no longer holds a charge, shuts down unexpectedly, or fails to power on. Dimensions are 54.05 × 34.10 × 5.40mm — measure your existing cell before installing.

• E300 platform fit: The E300 uses a compact single-cell Li-ion pack at 3.7V nominal. The connector pinout and physical footprint must match exactly — this cell meets both. No modification needed to seat it in the battery bay.
• Bench tested on actual hardware: We ran charge and discharge cycles on this cell and monitored BMS cutoff behavior at both ends. The protection circuit trips correctly at low-voltage cutoff and does not allow overcharge beyond the rated ceiling.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging begins on an uncalibrated pack.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under modem or screen load that the IC does not anticipate. The phone reads 25% but the cell voltage has already dropped below the cutoff threshold under load. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter to the correct baseline.

Phone not powering on after the cell sat in storage

Li-ion cells self-discharge in storage. If this battery was stored for an extended period, the cell voltage may have dropped below 2.5V, triggering BMS lockout. The phone will show nothing — no charging indicator, no boot screen. Connect to a wall adapter and leave it undisturbed for 15–20 minutes before attempting to power on; the BMS needs a trickle current to recover enough voltage to re-initialise.