Asus ZenPad 8.0 Power Case Replacement Battery 3.7V 4150mAh

Asus ZenPad 8.0 Power Case CB81 — 3.7V Li-Polymer Replacement Battery (C11P1414)

This is a 3.7V, 4150mAh lithium-polymer replacement for the C11P1414 cell inside the Asus ZenPad 8.0 Power Case (model CB81). The CB81 is a protective case with an integrated battery pack that charges the ZenPad 8.0 tablet directly. When this internal cell degrades, the case stops delivering charge — this battery restores that function.

• CB81 Power Case compatibility: The CB81 uses a single-cell Li-Polymer pack at 3.7V nominal, feeding the case's onboard charge IC which then pushes current to the tablet over the pogo-pin connector. Cell voltage and physical dimensions must match exactly — a mismatched cell confuses the charge IC and prevents output.
• Bench tested on actual hardware: We cycled this cell through the CB81's charge IC and confirmed BMS handshake, proper cutoff at low-voltage threshold, and stable output current to the tablet connector without thermal events.
• Fuel gauge recalibration after swap: After fitting this cell, run the case down to automatic shutoff, then charge it uninterrupted to 100% before disconnecting. This one full cycle resets the fuel gauge IC against the new cell's actual capacity and clears the inaccurate percentage readings that appear immediately after a swap.

Why the CB81 case stops passing charge to the tablet before its indicator LED dies

The CB81's charge IC monitors cell voltage continuously. When the internal cell ages, its voltage sags under load even if it still reads partially charged at rest. The IC sees this sag, interprets it as an unsafe discharge condition, and cuts output to the tablet — even though the case LED still shows remaining capacity. The cell voltage under load, not the LED reading, controls whether the tablet receives charge. Replacing the degraded cell eliminates the sag and restores consistent pass-through output.

CB81 case showing full charge but delivering no power to the ZenPad

This happens when the internal cell has degraded to the point where its resting voltage looks normal but collapses the moment the charge IC draws current. The IC detects the voltage collapse, trips its protection circuit, and blocks all output — so the tablet sees nothing on the pogo pins. A multimeter on the cell under a small load will show voltage dropping well below 3.4V if this is the cause. Replacing the C11P1414 cell and running one full charge cycle restores stable output voltage to the tablet connector.