About this replacement
Acer Iconia Tab A1-840 — 3.7V Li-Polymer Replacement Battery (KT.00109.001)
This is a 3.7V 4000mAh (14.8Wh) Li-Polymer battery for the Acer Iconia Tab A1-840 and A1-840FHD series 8-inch Android tablets. It replaces OEM part numbers KT.00109.001 and 30107108. Capacity matches the original cell specification from the product data.
- A1-840 and A1-840FHD series compatibility: The A1-840, A1-840FHD-10G2, A1-840FHD-197C, and A1-840-131U all share the same 3.7V cell format, connector pinout, and BMS handshake protocol — one battery fits the full line without modification.
- Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the A1-840 platform. The BMS accepted the cell on first connection, communicated state-of-charge correctly to Android, and held the charge IC in normal operation throughout.
- Fuel gauge reset after installation: After fitting this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100% without using the device. This forces the fuel gauge IC to recalibrate against the new cell and clears the inaccurate percentage readings that appear immediately after a swap.
Tablet shutting down at 15–25% remaining after battery swap
This happens when the fuel gauge IC is still calibrated to the old degraded cell's discharge curve. The Android power system reads a false floor and triggers shutdown before the new cell is actually empty. Combined load from the display backlight and active WiFi accelerates the voltage drop and triggers the cutoff earlier. Run one full discharge to automatic shutoff followed by an uninterrupted charge to 100% — after that single cycle, the shutdowns at 15–25% stop.
Fast charging not available after battery replacement
The A1-840 charge IC negotiates charge rate during the first accepted cycle. If the tablet detects a new cell mid-session or the cycle is interrupted, it defaults to a conservative charge rate and may not re-negotiate on subsequent plugs. Use the original Acer charger and let the first charge run from near-zero to 100% without interruption. After that cycle completes, normal charge rate resumes and is maintained on all following charges.