ZIKOM Z650 Replacement Battery 3.7V 750mAh Li-ion

ZIKOM Z650 / Z660 / Z710 — 3.7V Li-ion Replacement Battery

This is a 3.7V 750mAh Li-ion cell for the ZIKOM Z650, Z660, and Z710 smartphones. It replaces an original cell that has degraded, lost capacity, or stopped holding a charge. No OEM part number is published for this battery — the fit is confirmed by voltage rail and physical dimensions (53.00 × 33.90 × 5.70mm).

• Z650 / Z660 / Z710 compatibility: These three models share the same battery bay dimensions and 3.7V single-cell architecture. The connector pinout and BMS handshake protocol are identical across the trio, so one cell covers all three variants.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the Z650 platform. The BMS accepted charge handshake on the first connection, held voltage above 3.5V through the discharge curve, and triggered cutoff cleanly at the low-voltage threshold without tripping a BMS lockout.
• Fuel gauge recalibration on first use: On first install, disable fast charging if your Z650 supports it, then run one complete discharge down to auto-shutdown followed by a full uninterrupted charge. This gives the fuel gauge IC a clean reference curve for the new cell before high-current cycles begin.

Why the Z650 reports the wrong battery percentage after a cell swap

The Z650 uses a fuel gauge IC that builds its capacity model from coulomb counting over previous charge cycles. When a new cell goes in, the IC still references the old cell's discharge curve, so the percentage shown on screen does not match actual remaining charge. This mismatch is worst in the 30–15% range, where the old curve diverged most sharply from the new cell. One full discharge-to-shutdown followed by a charge to 100% resets the coulomb counter and gives the IC a fresh baseline. After that single cycle, percentage reporting should track the new cell accurately.

Sudden shutdown at 20–25% on the replacement cell

This happens when the fuel gauge IC is still calibrated to a degraded original cell that had a steep voltage cliff near end-of-charge. The new cell has a different discharge curve, and under screen or modem load the IC misreads remaining capacity and allows the system to draw down past the actual safe floor. The phone cuts out because the cell voltage drops below 3.0V under load before the OS registers a low-battery warning. Run one full uninterrupted discharge cycle to let the IC recalibrate — after recalibration, the cutoff point should shift back toward 5–8% as expected.