Sharp Aquos Pad SHT21 Replacement Battery 3.7V 3300mAh

Sharp Aquos Pad SHT21 — 3.7V Li-Polymer Replacement Battery (UBATIA211AFN3)

This is a 3.7V, 3300mAh lithium-polymer replacement battery for the Sharp Aquos Pad SHT21 tablet. It fits the original battery slot and matches the OEM part number UBATIA211AFN3. If your Aquos Pad no longer holds a charge or shuts down unexpectedly, this cell restores power to the display, processor, and internal components.

• Aquos Pad SHT21 fitment: The SHT21 uses a flat Li-Polymer pouch cell at 3.7V nominal. The connector pinout and cell dimensions — 122.30 x 80.00 x 3.40mm — match the original bay. The charge IC on this tablet communicates directly with the cell's protection circuit, so voltage spec and BMS thresholds have to align exactly.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the SHT21 platform. The protection circuit tripped correctly at the low-voltage cutoff, and the charge IC accepted the cell without throwing a fault state on the first accepted cycle.
• Fuel gauge reset after swap: After fitting this battery, run the tablet down to automatic shutoff, then charge it uninterrupted to 100% before using it again. This gives the fuel gauge IC a clean reference point against the new cell and clears the inaccurate percentage readings that commonly appear right after a swap.

Aquos Pad SHT21 shutting down at 15–25% remaining

The SHT21 drives a power-hungry display alongside a WiFi radio, and that combined load pulls the cell voltage down sharply in the lower charge range. If the old cell was degraded, the fuel gauge IC was calibrated to that weaker voltage curve. After fitting a new cell, the gauge still uses the old curve, so the tablet hits its shutdown threshold well before the cell is actually empty. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% recalibrates the gauge. After that cycle, the tablet should stay on until the display reads below 5%.

Fast charging unavailable after fitting a replacement cell

The SHT21's charge IC uses a handshake with the battery's protection circuit to confirm it can push a higher charge current safely. On a fresh cell, this handshake does not always complete on the very first plug-in. Connect the tablet to its original charger and let it run one full charge cycle to 100% without interruption. After that completed cycle, the charge IC logs the cell as verified and fast charge becomes available on subsequent sessions. Using a third-party or lower-rated cable on the first charge can prevent the handshake from completing — use the OEM cable for that first cycle.