About this replacement
Sharp Aquos R / SH03J / SHV39 / 605SH — 3.8V Li-Polymer Replacement Battery (UBATIA280AFN1)
This is a 3.8V, 3050mAh Li-Polymer cell built to the UBATIA280AFN1 specification for the Sharp Aquos R smartphone. It fits four model variants: Aquos R, SH03J, SHV39, and 605SH — all share the same battery bay, connector, and BMS communication protocol. Capacity figure is taken directly from the product specification, not extrapolated from a third-party source.
- Aquos R variant compatibility: The SH03J, SHV39, and 605SH are regional releases of the same Aquos R hardware platform. They share an identical voltage rail at 3.8V nominal, the same physical connector pinout, and the same BMS handshake expected by Sharp's charge IC — so one cell specification covers all four models without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, monitoring BMS communication at the connector. The protection circuit responded correctly to both over-voltage cutoff and low-voltage lockout thresholds, and the charge IC accepted the cell without triggering a fault flag on the host board.
- Fuel gauge recalibration on first cycle: After installation, disable fast charging and run one complete discharge down to automatic shutdown, then charge to 100% on a standard 5V supply. The Aquos R's coulomb counter needs a full reference cycle against the new cell's actual discharge curve before its percentage readings stabilise — skipping this step is the most common cause of erratic percentage jumps in the first week of use.
Sudden shutdown at 20–30% on the Aquos R after a cell swap
The Aquos R's modem and display together can pull sharp current spikes during calls or screen-on bursts. A new Li-Polymer cell has a slightly different internal resistance profile than the aged cell the fuel gauge IC was originally calibrated against. At around 20–30% state of charge, the cell voltage under that load drops faster than the IC expects and crosses the hardware cutoff threshold — the phone reads 25% on screen but the cell is already at the low-voltage floor. Running one full reference discharge-charge cycle as described above recalibrates the coulomb counter and eliminates most of these premature shutdowns. If shutdowns persist after two full cycles, check that the connector is fully seated — a partial connection raises effective impedance and amplifies the voltage sag.
USB-PD or fast charge not accepted on the first charge after replacement
Sharp's charge IC performs a negotiation handshake with the BMS on the new cell before allowing elevated charge current. On the very first cycle, some cells present a slightly higher impedance reading than the IC's threshold for fast-charge authorisation — the phone defaults to standard 5V charging as a safety measure, not a fault. This is not a defective cell. Charge the phone once at standard rate to roughly 50%, then disconnect and reconnect the charger — the IC re-runs the handshake against the now partially charged cell and typically authorises fast charge from that point forward. If fast charge still does not activate after two attempts, verify the cable supports the required current rating for Sharp's proprietary fast-charge protocol.