About this replacement
Acer Chromebook C720 / C720P — 11.25V Li-Polymer Replacement Battery (AP13J3K)
This 11.25V, 3950mAh (44.44Wh) Li-Polymer battery fits the Acer Chromebook C720, C720P, and C720-3404, along with the broader Chromebook 11.6" line. It replaces OEM part numbers AP13J3K, AP13J4K, AP13J7K, KT.00304.001, and several related variants. When the original cell degrades and the Chromebook no longer holds a charge, this is the direct cell swap.
- C720 series compatibility: The C720, C720P, and adjacent 11.6" variants share the same 11.25V three-cell architecture, connector pinout, and BMS handshake protocol — which is why a single AP13J3K cell covers all of them. Swapping between those sub-models does not require a different battery.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a C720P unit. The BMS negotiated correctly, charge termination triggered at full capacity, and the protection circuit responded to over-discharge cutoff at the expected low-voltage threshold without latching fault states.
- Post-swap learn cycle on ChromeOS: After fitting this cell, run the Chromebook down until it hibernates on its own — do not force shutdown. Then charge it uninterrupted to 100%. This gives the fuel gauge IC one complete reference cycle against the new cell chemistry and clears the inaccurate capacity reading ChromeOS logs after every cell replacement.
Why ChromeOS flags poor battery health immediately after a cell swap
The Chromebook's embedded controller reads health data from EEPROM registers that were written by the original factory cell. A new cell resets the physical chemistry but not those stored values, so ChromeOS compares current readings against outdated baseline figures and logs a health warning. This is a data mismatch — not a fault with the replacement cell. Running one complete discharge-to-hibernate then a full uninterrupted charge allows the fuel gauge IC to rewrite its reference data against the new cell. After that cycle, the health warning clears on its own.
Chromebook shutting down at 20–30% charge shown on screen
This happens when the cell voltage drops below what the CPU and display draw can sustain under load — even though the fuel gauge still shows capacity remaining. The gauge is reading average voltage, not instantaneous load voltage, so there's a gap between what it displays and what the cell can actually deliver under full-system draw. It becomes more visible in an aged or deeply discharged cell that hasn't been calibrated. Run the learn cycle described above — one full discharge to hibernate cutoff, then charge to 100% — and confirm the shutdown threshold moves back down toward 5% or lower.