About this replacement
Oppo U707T / U2S / U707 — 3.8V Li-ion Replacement Battery (BLP553)
This is a 3.8V, 2800mAh Li-ion replacement battery carrying OEM part number BLP553. It fits the Oppo U707T, U2S, and U707 smartphones. Direct swap for a degraded or failed original cell — same voltage, same capacity, same connector footprint.
- U707T / U2S / U707 platform fit: All three models share the BLP553 form factor — same 88.05 × 55.90 × 4.60mm cell, same 3.8V nominal rail, and the same BMS connector pinout. One cell covers the full range without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench, confirming the BMS communicates correctly with the charge IC and that protection circuits trip at the expected over-discharge threshold rather than cutting out prematurely under load.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before the coulomb counter starts reporting to the OS — skipping this step causes erratic percentage readings for the first several days.
Sudden shutdown at 20–30% on a replacement cell
This is a voltage cliff problem, not a capacity problem. A new cell has a slightly different discharge curve than the original, so the fuel gauge IC — still calibrated to the old cell — misjudges how much usable voltage remains. When the modem or screen pulls a high-current burst, the cell voltage drops below the BMS cutoff threshold before the OS ever reads 0%. Running one full discharge cycle to actual cutoff, then a full charge, teaches the coulomb counter where the real floor sits and eliminates the premature shutdown.
Phone warm near the battery during the first few charges
A fresh cell typically starts with higher internal impedance than a broken-in one. The charge IC pushes current into that higher resistance, and the extra heat is normal for the first two or three cycles. If warmth is localized to the battery compartment and fades after cycle three, nothing is wrong. If heat spreads to the rear camera area or persists past cycle five, pull the battery and check the connector seating — a misaligned pin forces the charge IC to work harder than the circuit expects.