Mobistel EL400 Replacement Battery BTY26170 3.7V 1500mAh

Mobistel EL400 — 3.7V Li-ion Replacement Battery (BTY26170)

This is a 3.7V, 1500mAh Li-ion cell for the Mobistel EL400 mobile phone. It replaces OEM part BTY26170 directly. If the original battery swells, fails to hold charge, or causes unexpected shutdowns, this cell restores normal device operation.

• EL400 compatibility: The EL400 uses a single-cell 3.7V Li-ion pack with a standard contact layout. This replacement matches that voltage rail and physical footprint — 66.00 × 43.50 × 5.00mm — so the battery seats correctly and the charge IC communicates without error.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the EL400 platform. The BMS accepted the cell without triggering a fault state, and the charge IC cycled through CC-CV without error across repeated passes.
• Fuel gauge recalibration on first cycle: On first use after installation, disable fast charging and let the phone complete one full discharge-charge cycle. This gives the fuel gauge IC a clean reference curve for the new cell before high-current charging runs against an uncalibrated coulomb counter.

Sudden shutdown at 20–30% on a replacement cell

A new Li-ion cell has a slightly different voltage-discharge curve than the aged cell it replaces. The fuel gauge IC on the EL400 was calibrated against the old cell's curve, so it misreads the remaining capacity. When the phone hits a load spike — modem handshake, screen brightness burst — the cell voltage drops below the BMS cutoff threshold even though the OS still shows charge remaining. One full discharge-charge cycle resets the coulomb counter and brings the percentage reporting back in line with actual cell state.

Phone warm near the battery compartment during first charge

A fresh cell arrives with higher internal impedance than a broken-in one. The charge IC pushes current into that higher resistance, and some of that energy converts to heat rather than stored charge. This is normal on the first one or two cycles and settles as the cell's impedance drops. If the phone stays warm beyond the third charge cycle, check that the charge IC is not stuck in a continuous CC phase — verify the port connection and confirm the voltage at full charge reaches 4.2V.