Asus Zenpad Z8S Replacement Battery 3.85V 4550mAh

Asus Zenpad Z8S / ZT582KL — 3.85V Li-Polymer Replacement Battery (C11P1615)

This is a 3.85V, 4550mAh lithium-polymer cell replacing the original C11P1615 battery in the Asus Zenpad Z8S (ZT582KL, P00J). It fits the compact Android tablet directly, restoring power where the degraded original cell causes premature shutdowns or rapid capacity loss. Capacity figure is sourced from product data — 17.52Wh total energy.

• Zenpad Z8S / ZT582KL / P00J compatibility: All three model designations reference the same hardware platform. They share an identical connector, the same 3.85V charging rail, and the same BMS handshake expected by the charge IC on the motherboard — one cell fits all three.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the ZT582KL platform. The BMS accepted the cell without fault codes, charge termination triggered correctly at the top of the voltage curve, and the protection circuit tripped cleanly at the low-voltage cutoff threshold.
• Fuel gauge recalibration after swap: After fitting this cell, run one full discharge to automatic shutoff — do not manually power off — then charge uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell's actual capacity curve and clears inaccurate percentage readings that commonly appear after a battery swap.

Zenpad Z8S shutting down at 15–25% remaining

This happens when the display backlight and active WiFi run simultaneously at full brightness — combined draw creates a brief voltage sag. On an aged or freshly swapped cell that hasn't been calibrated, the BMS reads the sag as a low-voltage event and triggers a protective shutdown before the actual charge is depleted. The fuel gauge IC is calibrated to the old cell's internal resistance profile, so its percentage estimate goes wrong under load. Run the full discharge-to-shutoff recalibration cycle described above — that single cycle corrects the gauge against the new cell's resistance curve and eliminates the premature cutoff.

Fast charging unavailable on the Zenpad Z8S after a battery swap

The Zenpad Z8S charge IC uses a proprietary negotiation handshake before allowing elevated charge current — it doesn't accept USB-PD at the first session on a new cell. This is a one-cycle limitation, not a hardware fault. Connect the tablet to the original Asus adapter and let it complete one full charge from low to 100% without interruption. After that first accepted cycle, the charge IC logs the cell as initialised and fast charge current resumes on subsequent sessions.