AT&T Vivid 4G BH39100 Replacement Battery 3.7V 1600mAh

AT&T Vivid 4G — 3.7V Li-ion Replacement Battery (BH39100)

This is a 3.7V, 1600mAh Li-ion cell that replaces the original battery in the AT&T HTC Vivid 4G smartphone. It fits the internal battery bay and connects via the standard flex-tab connector on the Vivid 4G mainboard. OEM part numbers BH39100, 35H00167-00M, 35H00167-01M, and 35H00167-03M all cross-reference to this cell.

• Vivid 4G compatibility: The Vivid 4G uses a fixed 3.7V single-cell architecture with a dedicated charge IC on the mainboard. Any replacement cell must match that voltage rail exactly — mismatched cells cause the charge IC to reject the battery or report incorrect charge states from the first cycle.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Vivid 4G mainboard. The BMS accepted the cell without fault codes, and the charge IC stepped through trickle, constant-current, and constant-voltage phases as expected on a healthy cell.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the Vivid 4G's fuel gauge IC one complete reference cycle against the new cell's discharge curve before it starts reporting accurate percentages.

Why the Vivid 4G reports wrong battery percentage after a cell swap

The Vivid 4G uses a coulomb-counting fuel gauge IC that builds its charge model against the cell it was last calibrated on. When you install a new cell, that stored model no longer matches the actual discharge curve of the fresh chemistry. The gauge reads voltage and estimates state-of-charge against the old curve, which produces inflated or deflated percentage readings. One full uninterrupted discharge-to-shutdown followed by a complete charge resets the coulomb counter and rebuilds the model against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This happens when the modem or display draws a current spike the cell cannot sustain at low state-of-charge — voltage drops below the BMS cutoff threshold even though the gauge still shows charge remaining. The fuel gauge IC hasn't yet mapped where the voltage cliff sits on the new cell's curve, so it doesn't warn the OS in time. After the first full calibration cycle, the gauge learns the real cutoff point and the OS receives a low-battery warning before the hard shutdown occurs. If shutdowns persist past two full cycles, check that the flex-tab connector is fully seated — a partial connection raises contact resistance and amplifies voltage sag under load.