Verizon Jest TXT8040 Replacement Battery BTR-8030 3.7V 800mAh

Verizon Jest TXT8040 — 3.7V Li-ion Replacement Battery (BTR-8030)

This is a 3.7V, 800mAh Li-ion replacement battery for the Verizon Jest TXT8040, TXT8040, Razzle, and PCD8030. It replaces OEM parts BTR-8030, BTR-8030B, and VZW8030BAT. When the original cell degrades and the phone can no longer hold a charge through a normal day of texting and calls, this cell restores that capacity.

• Jest / Razzle platform compatibility: The TXT8040, Razzle, and PCD8030 all share the same 3.7V cell footprint, connector pinout, and BMS handshake logic — which is why all four models pull from the same OEM part number range. The 51.80 × 37.60 × 4.70mm form factor fits the battery bay without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the TXT8040 platform and confirmed the BMS accepted the cell, reported charge state correctly after one full cycle, and did not trigger premature cutoff under normal messaging and call load.
• Fuel gauge recalibration after install: On first use after fitting this cell, run one complete discharge down to auto-shutdown and then charge uninterrupted to 100%. The fuel gauge IC in this phone calibrates its coulomb counter against a full discharge curve — skipping this step causes the percentage readout to drift and the phone to report incorrect charge levels for weeks.

Why the Jest TXT8040 reports the wrong battery percentage after a cell swap

The TXT8040 uses a simple fuel gauge IC that builds its charge model from the original cell's discharge curve. When a new cell goes in, the IC still references the old curve — so the percentage it displays can be off by 15–25% until it relearns. The only way to force a recalibration is a full discharge-to-shutdown followed by an uninterrupted full charge. After that single cycle, the IC locks onto the new cell's actual voltage-to-capacity relationship and the readout stabilises. If the percentage still jumps erratically after two full cycles, check that the battery contacts on the phone body are clean and making firm contact.

Sudden shutdown at 20–30% remaining on the replacement cell

This is a voltage cliff problem, not a capacity problem. At that state of charge, the cell's voltage drops sharply under the load spike from a call connecting or the screen backlight switching on — the phone's low-voltage protection cuts power before the fuel gauge even registers the drop. A new cell that hasn't completed its first calibration cycle makes this worse because the fuel gauge reports 25% when the actual usable charge is already near the cutoff threshold. Run one full discharge-charge cycle as described above. If the shutdowns persist, check the terminal voltage at rest with a multimeter — a healthy charged cell at 30% reported charge should read at least 3.6V.