BLU Vivo XI+ Replacement Battery C796438300P 3.85V 2800mAh

BLU Vivo XI+ — 3.85V Li-Polymer Replacement Battery (C796438300P)

This 3.85V, 2800mAh Li-Polymer cell is a direct replacement for the BLU Vivo XI+, Vivo XI Plus, and V0310WW. It restores full power to the processor, display, modem, and all onboard functions. Capacity is 10.78Wh, matching the original cell specification.

• Vivo XI+ / V0310WW platform fit: All three model designations share the same battery bay geometry, connector pinout, and BMS handshake protocol — one cell covers the full variant range without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Vivo XI+ platform. The BMS accepted charge initiation cleanly, protection thresholds triggered correctly at low voltage, and the fuel gauge IC tracked state-of-charge without erratic jumps after the first full cycle.
• First-cycle fuel gauge recalibration: On first use after installation, disable fast charging and complete one full discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging introduces error into the coulomb counter baseline.

Why the Vivo XI+ reports wrong battery percentage after a cell swap

The Vivo XI+ uses a fuel gauge IC that builds its capacity model from the original cell's discharge curve over time. When a new cell goes in, that learned curve no longer matches the new cell's actual voltage-to-capacity relationship. The result is percentage readings that are off by 10–20% or jump suddenly. One full discharge cycle — from 100% down to automatic shutdown, then a complete charge — forces the IC to remap against the new cell and correct its baseline.

Sudden shutdown at 20–30% remaining on the replacement cell

This happens when the modem or display draws a current spike the cell cannot sustain at that state-of-charge, causing terminal voltage to drop below the BMS cutoff threshold — even though the percentage display still shows capacity remaining. It is a voltage-sag failure, not a capacity failure. The fuel gauge IC has not yet recalibrated, so it reports 25% when the cell is actually near its voltage floor under load. Complete two full discharge-charge cycles at standard rate; if shutdown persists below 3.5V under screen-on load after that, the BMS trip threshold may need a reset by draining the cell fully to auto-shutdown before recharging.