About this replacement
Sony Xperia 1 V / 1 VI 5G — 3.89V Li-Polymer Replacement Battery (SNYSHD4)
This is a 3.89V, 4850mAh (18.87Wh) Li-Polymer cell that replaces the original SNYSHD4 battery in the Sony Xperia 1 V and Xperia 1 VI 5G. It fits both models because they share the same connector pinout, BMS handshake protocol, and physical cell envelope. Capacity figures are taken directly from product data — not estimated.
- Xperia 1 V and 1 VI 5G compatibility: Both models use the same SNYSHD4 cell format, voltage rail, and fuel gauge IC communication protocol. The same replacement cell satisfies the BMS check on both devices without any firmware conflict.
- Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Xperia 1 V and confirmed the BMS accepted the cell, fast charge protocols initialised correctly after one calibration cycle, and the coulomb counter tracked capacity without erratic jumps.
- Fuel gauge recalibration on first use: After installation, disable fast charging and complete one full discharge-to-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated cell — otherwise the percentage display will read inaccurately from the start.
Sudden shutdown at 20–30% on the Xperia 1 V after a cell swap
This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The new cell hits a voltage cliff under modem or display load at a state-of-charge the IC hasn't mapped yet. The phone reads 25% but the cell voltage has already dropped below the safe cutoff threshold. One full discharge-charge cycle without fast charging resets the coulomb counter and eliminates this behaviour.
USB-PD fast charge not working on first cycle after replacement
On the first charge after installation, the charge IC on the Xperia 1 V may refuse to negotiate the USB-PD fast charge contract with an uncalibrated cell. It defaults to standard 5V charging as a protection measure. This is expected behaviour — complete the first full cycle at standard rate. Fast charge typically resumes normally from the second cycle once the BMS has logged a baseline impedance reading for the new cell.