About this replacement
Motorola Xoom Family Edition MZ505 — 3.7V Li-Polymer Replacement Battery (BATBJA0L21)
This 3.7V 6700mAh lithium-polymer battery replaces the original BATBJA0L21 cell in the Motorola Xoom Family Edition tablet. It fits the MZ505 and Xoom 10.1 variants. The battery powers the display, processor, wireless radios, and all active applications on these 10-inch Android tablets.
- MZ505 and Xoom 10.1 compatibility: All three listed models share the same charge IC, connector pinout, and BMS handshake protocol. The BATBJA0L21 part number covers the full Xoom Family Edition lineup — no hardware differences affect fitment across these variants.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on an MZ505 unit. The BMS accepted the new cell without fault codes, completed a full charge curve normally, and the charge IC held steady at the expected termination voltage.
- Fuel gauge reset after installation: After fitting the new battery, run the tablet down to automatic shutoff from a full charge, then charge it uninterrupted to 100%. This forces the fuel gauge IC to recalibrate against the new cell's actual capacity curve and corrects the inaccurate percentage readings that appear right after a swap.
Tablet shutting down at 15–25% remaining after battery replacement
This happens when the fuel gauge IC is still calibrated to the old, degraded cell. The reported percentage no longer maps correctly to actual cell voltage. Under combined display and WiFi load, voltage drops sharply at a point the IC doesn't recognise as low — triggering an emergency shutdown before the reading hits zero. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% resets the calibration and eliminates the premature cutoff.
Percentage dropping faster than expected from 100% on the Xoom MZ505
A new cell has a different internal resistance profile than the worn cell the fuel gauge was trained on. The IC misreads the voltage slope and reports capacity draining faster than it actually is. This is gauge drift, not a defective battery. Run one complete cycle — full discharge to automatic shutoff, then a full uninterrupted charge — and the gauge recalibrates to the 6700mAh capacity of the replacement cell.