Lively 5049SJBS2 Replacement Battery 3.85V 3000mAh

Lively 5049SJBS2 — 3.85V Li-Polymer Replacement Battery

This 3.85V, 3000mAh (11.55Wh) lithium-polymer cell is a direct replacement for the Lively 5049SJBS2 smartphone. It fits the exact footprint at 76.90 × 62.26 × 3.40mm and matches the voltage rail the device's charge IC expects. If your original cell is swelling, dropping charge quickly, or failing to hold a reading, this replaces it.

• 5049SJBS2 fit confirmation: The Lively 5049SJBS2 uses a fixed connector and BMS handshake tied to cell voltage — this battery matches the 3.85V nominal required for the charge IC to accept the cell and begin the CC/CV charge cycle without triggering a fault state.
• Bench tested on actual hardware: We cycled this cell through charge and discharge under both standby and active screen loads. The BMS responded correctly at high-state-of-charge cutoff and did not trip on reconnection — a common failure point on fresh lithium-polymer cells with stiff internal impedance.
• Fuel gauge recalibration after installation: Disable fast charging for the first complete discharge-charge cycle after fitting this cell. The fuel gauge IC is still calibrated to your old cell's discharge curve — running one slow cycle first lets it remap against the new cell before high-current charging begins.

Why the 5049SJBS2 reports wrong battery percentage after a cell swap

The Lively 5049SJBS2 uses a coulomb-counter-based fuel gauge IC that builds its charge model against the cell it learned on. When you install a new cell, the IC still references the old discharge curve — so percentage readings drift or jump. This is not a fault with the new battery. One full discharge to auto-shutdown followed by a complete charge to 100% forces the IC to rewrite its learned curve against the new cell's actual capacity. After that single cycle, percentage accuracy normalises.

Sudden shutdown at 20–30% on the replacement cell

This happens because the new cell's open-circuit voltage looks fine at rest, but under modem transmission or screen-backlight load, it sags below the BMS cutoff threshold — typically around 3.0V per cell — before the fuel gauge registers the drop. The OS reads 25% and the phone cuts out without warning. The fix is that first calibration cycle: discharge the phone fully under normal use until it shuts itself off, then charge uninterrupted to 100%. After calibration, the fuel gauge tracks the voltage sag pattern of the new cell and fires the low-battery warning before the BMS hard-cuts at 3.0V.