Cubot S550 Compatible Battery 3.8V 2800mAh Li-Polymer

Cubot S550 — 3.8V Li-Polymer Replacement Battery (S550)

This is a 3.8V, 2800mAh Li-Polymer battery for the Cubot S550 Android smartphone. It fits directly into the S550 and replaces a cell that has degraded through repeated charge cycles. Capacity figures are taken from the product specification, not estimated from third-party sources.

• S550 platform fitment: The S550 uses a specific cell footprint and connector orientation tied to its battery bay dimensions. This replacement matches the OEM cell voltage rail at 3.8V nominal, which the charge IC expects before enabling the charging path.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the S550 platform. The BMS accepted the charge handshake without fault flags, and the protection circuit triggered correctly at low-voltage cutoff.
• 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 map its readings against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC on the S550 is still using the discharge curve from the old, degraded cell. The new cell's voltage drops more steeply under modem and screen load than the IC expects, so the phone interprets a voltage cliff as a near-empty state and shuts down. It is not a fault with the replacement cell. Run one full discharge to below 5% and then a full charge to 100% without interruption — this forces the coulomb counter to reset its endpoints against the new cell. After that cycle, percentage reporting stabilises.

Phone feels warm near the battery during the first charge

A new Li-Polymer cell starts with higher internal impedance than a cell that has completed several cycles. The charge IC pushes current into this higher-resistance cell, and that resistance converts some energy to heat. This is normal on the first one or two charge cycles and settles as the cell forms. If the warmth continues past the third full charge, check that the replacement cell is seated flat against the battery bay with no edge lifted — an unseated cell traps heat and raises impedance further.