BBK VIVO X5 MAX B-78 Compatible Battery 3.8V 2000mAh

BBK VIVO X5 MAX Series — 3.8V Li-Polymer Replacement Battery (B-78)

This is a 3.8V, 2000mAh Li-Polymer cell that replaces part number B-78 in the VIVO X5 MAX, X5 MAX+, X5 MAX V, and X5MAX L smartphones. It restores power to a phone that no longer holds a charge or shuts down unexpectedly. Physical dimensions are 101.70 x 49.97 x 2.56 mm — measure your original before ordering if you are unsure of your exact variant.

• X5 MAX variant compatibility: The MAX, MAX+, MAX V, and MAX L all share the same battery bay dimensions and connector pinout, so B-78 spans the full lineup. The BMS handshake protocol and voltage rail are identical across these variants.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the X5 MAX platform and confirmed the BMS communicates correctly with the charge IC — no charge rejection on the first cycle and no thermal fault triggers during a standard 5V/1A charge session.
• First-cycle fast charge lockout: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff, not a capacity problem. Under peak load — mobile data, display brightness, or a CPU spike — the new cell's voltage drops faster than the fuel gauge IC expects based on the old cell's discharge curve stored in NVRAM. The phone interprets the voltage sag as a critically low state and cuts power to protect the system. One full uninterrupted discharge-charge cycle resets the coulomb counter and maps the new cell's actual discharge profile. After calibration, shutdowns at 20–30% should stop.

Phone won't power on after sitting in storage with a flat battery

If the cell has self-discharged below approximately 2.5V during storage, the BMS enters a protection lockout and blocks all current flow — the phone appears completely dead. Connect to a wall charger, not a PC USB port, and leave it untouched for 15–20 minutes. The charge IC will trickle current into the cell at a low rate until the voltage climbs above the BMS recovery threshold, at which point normal charging resumes. If the phone still shows no sign of charging after 30 minutes, check that the charger output is at least 5V/1A.