EB504465VU T-Mobile SGH-T839 Replacement Battery 3.7V 1500mAh

T-Mobile SGH-T839 — 3.7V Li-ion Replacement Battery (EB504465VU)

This is a 3.7V, 1500mAh Li-ion cell for the T-Mobile SGH-T839 sliding QWERTY smartphone. It replaces OEM part numbers EB504465VU, EB504465VK, EB504465VA, EB504465VUBSTD, and B564465LU. Dimensions are 64.60 × 43.90 × 5.20mm — confirm these against your existing cell before installing.

• SGH-T839 fit note: The T839 uses a standard contact plate with no NFC or secondary authentication handshake, so the replacement cell slots in without firmware negotiation — the phone reads voltage directly from the contact pads without a BMS pairing step.
• Bench tested on actual hardware: We cycled this cell through charge and load on the bench. The BMS held cutoff voltage cleanly at both ends — no false low-battery triggers during the discharge curve, and charge termination stopped current at the correct upper threshold.
• Fuel gauge recalibration on first use: On first installation, run one full discharge down to automatic shutdown, then charge uninterrupted to 100% without using the phone. This gives the T839's fuel gauge IC a complete reference curve against the new cell — skipping this step causes erratic percentage readings in early use.

Why the SGH-T839 reports wrong battery percentage after a cell swap

The T839 tracks charge state using a fuel gauge IC calibrated to the discharge curve of the original cell. A new cell has a different internal resistance profile, so the IC's stored curve no longer matches actual voltage behaviour. The phone reads voltage at set intervals and maps it to a percentage — if the curve is wrong, the mapping is wrong. One complete uninterrupted discharge-to-charge cycle overwrites the old reference and re-anchors the gauge to the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops below the modem's minimum operating threshold under radio transmission load — even though the fuel gauge still shows charge remaining. The T839's EDGE radio and screen backfire together pull current spikes the gauge doesn't track in real time. The cell voltage sags below 3.5V under that combined load and the phone cuts out. After one full calibration cycle the gauge corrects its empty threshold and the shutdowns stop.