HTC P4000 Replacement Battery 3.7V 2600mAh 35H00077-00M

HTC P4000 / Mogul / Titan 6800 — 3.7V Li-ion Replacement Battery (35H00077-00M)

This 3.7V Li-ion cell replaces the original battery in the HTC P4000, Mogul, Titan 100, and Titan 6800. Capacity is 2600mAh (9.62Wh), matching the OEM specification. The cell fits the original battery bay and connects to the same three-contact terminal the phone uses for fuel gauge communication.

• P4000 / Mogul / Titan platform compatibility: All four models share the same battery bay dimensions, voltage rail, and three-pin connector layout. The BMS handshake protocol is consistent across this platform, so the same cell works in each device without modification.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Titan 6800 platform. The BMS accepted charge without cutoff anomalies, and the fuel gauge IC responded correctly to the cell's discharge curve across the full voltage range.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and complete one full discharge-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging begins on an uncalibrated cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff issue, not a capacity problem. Under modem load or screen-on draw, the cell voltage drops sharply below the threshold the phone's power management IC uses to sustain operation — even if the fuel gauge still shows 20–30% remaining. The fuel gauge IC inherited its calibration from the old, degraded cell, so its percentage estimate no longer maps accurately to the new cell's actual voltage curve. One full discharge to automatic shutoff, followed by a complete charge to 4.2V, forces the coulomb counter to recalibrate against the new cell.

Phone warm near the battery compartment on the first few charges

A new cell typically has higher internal impedance than a broken-in one. The charge IC compensates by pushing slightly more voltage to maintain current, which generates heat at the cell surface during the first few cycles. This is normal and reduces as the cell's impedance settles with cycling. If the device feels hot rather than warm, or if charging stops before reaching 4.2V, check that the contacts on the battery are clean and seated flush against the phone's terminal pins.