BTR8045B USCellular TXT8045 Replacement Battery 3.7V 800mAh

USCellular TXT8045 / Verse — 3.7V Li-ion Replacement Battery (BTR8045B)

This is a 3.7V, 800mAh Li-ion cell built to replace part number BTR8045B in the USCellular TXT8045, TXT8045US, and Verse. It fits the original battery compartment and connects via the stock contact plate. Voltage and chemistry match OEM spec exactly.

• TXT8045 and Verse platform fit: The TXT8045, TXT8045US, and Verse all use the same 3.7V battery bay and BTR8045B contact layout. One cell covers all three variants — no adapter or modification needed.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the TXT8045 platform. The BMS accepted the charge current without fault, and the protection circuit tripped correctly at low-voltage cutoff — no thermal events, no false overcharge flags.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle before resuming normal use. The fuel gauge IC calibrates its discharge curve against the new cell during this first cycle — skipping it can cause the percentage meter to read inaccurately for days.

Sudden shutdown at 20–30% on the TXT8045 after a cell swap

The TXT8045 fuel gauge IC uses a stored discharge curve from the previous cell to predict remaining capacity. When a new cell goes in, that curve no longer matches the actual voltage profile of the fresh battery. At around 20–30% displayed charge, the new cell's voltage drops faster than the old curve predicts under modem or screen load — the phone reads it as a hard cutoff and shuts down. Running one full discharge cycle from 100% to auto-off, then charging uninterrupted to 100%, rewrites the calibration table. After that cycle, the percentage reading stabilises and shutdowns stop.

Battery percentage jumping erratically in the first few days after replacement

Erratic percentage jumps — 15% down in ten minutes, then a sudden recovery — point to an uncalibrated coulomb counter, not a faulty cell. The TXT8045 charge IC tracks energy in and out, but after a cell swap the counter loses its reference baseline. High-draw events like a cellular data burst or screen-on during charging expose the miscalibration as a visible jump. Let the phone complete two full uninterrupted charge cycles — charge to 100% with the screen off, then use normally until auto-shutdown — and the counter resets to the new cell's actual capacity at 800mAh.