About this replacement
Acer Iconia B1-720 Series — 3.7V Li-Polymer Replacement Battery (AP13PFJ)
This 3.7V, 2700mAh (9.99Wh) lithium-polymer battery replaces the AP13PFJ cell in the Acer Iconia B1-720 7-inch Android tablet. It fits the B1-720, B1-720-L864, B1-720-81111G01nki, and B1-720-L804 variants. All four share the same battery bay dimensions, connector pinout, and BMS handshake protocol.
- B1-720 variant compatibility: The B1-720 lineup uses a single battery specification across all regional SKUs — same voltage rail, same flat Li-Polymer cell footprint (124 × 59 × 3.54mm), and the same four-pin connector with NTC thermistor line. No rewiring or adapter needed between variants.
- Bench tested on actual hardware: We ran this cell through the B1-720 charge IC and confirmed the BMS accepted the new cell without fault flags. The fuel gauge IC registered the full 2700mAh rated capacity once the pack completed an initialisation cycle.
- Fuel gauge IC reset after installation: After fitting the new battery, run one full discharge to automatic shutoff, then charge uninterrupted to 100%. This recalibrates the fuel gauge IC against the new cell's actual voltage curve and eliminates the inaccurate percentage readings that consistently appear after a swap.
Why the B1-720 shuts down at 15–25% remaining
The B1-720 runs its display backlight and WiFi radio on the same voltage rail. Under combined load, the cell voltage drops faster than the fuel gauge IC anticipates — especially on an aged or freshly swapped cell that hasn't been calibrated. The SoC interprets the voltage sag as a critically low state and triggers a hard shutdown to protect the cell, even though the reported percentage still looks reasonable. Running one full discharge cycle to automatic shutoff recalibrates the IC's voltage-to-percentage map and shifts the cutoff threshold back to where it belongs.
Tablet showing 0% and not responding after sitting unused for weeks
Li-Polymer cells self-discharge during storage. If the B1-720 sat unused long enough, the cell voltage may have dropped below the BMS's minimum recovery threshold — typically around 2.5V — causing the BMS to open the protection circuit and cut output entirely. The tablet won't respond to the power button and may show nothing on charge. Connect it to a wall charger and leave it undisturbed for 30–60 minutes; a compliant charger will trickle current through the BMS at a rate low enough to allow cell recovery. Once voltage climbs back above 3.0V, the BMS closes the circuit and normal charging resumes.