HTC TyTN II Replacement Battery KAS160 3.7V 1100mAh

HTC TyTN II / P4550 Kaiser — 3.7V Li-Polymer Replacement Battery (KAS160)

This is a 3.7V, 1100mAh Li-Polymer battery for the HTC TyTN II, also sold as the P4550 and Kaiser. It replaces OEM part numbers KAS160, KAIS160, 35H00088-00M, and 35H00086-00M. The cell fits the original battery bay and connects via the same multi-pin connector used across the Kaiser platform.

• Kaiser platform compatibility: The TyTN II, P4550, Kaiser, and Kaiser100 all share the same battery bay dimensions and connector pinout. HTC used a consistent voltage rail and BMS handshake across these variants, so one cell covers the full Kaiser series without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the TyTN II. The BMS negotiated correctly with the device charge IC, accepted full current from the start, and held voltage through screen-on and modem-active load without dropout.
• Fuel gauge recalibration on first use: After installing this cell, run one complete discharge down to automatic shutdown, then charge uninterrupted to 100% before heavy use. The TyTN II fuel gauge IC was calibrated to the original cell's discharge curve — a single full cycle lets it relearn against the new cell and report accurate percentages.

Why the TyTN II reports wrong battery percentage after a cell swap

The TyTN II uses a coulomb-counter fuel gauge IC that builds its percentage model from cumulative charge and discharge data on the original cell. When you swap the cell, that stored model no longer matches the new cell's actual discharge curve. The IC keeps applying the old curve, so the displayed percentage drifts from the real state of charge. One full discharge-to-shutdown followed by an uninterrupted charge to 100% forces the IC to reset its reference points against the new cell.

Sudden shutdown at 20–30% on the TyTN II after replacement

This happens when the fuel gauge IC has not yet recalibrated and the cell hits a voltage cliff under combined modem and display load before the displayed percentage reaches zero. The Li-Polymer cell's open-circuit voltage looks healthy, but under load it drops below the BMS cutoff threshold — typically around 3.0V — and the device shuts off hard. The fix is the same recalibration cycle: discharge fully to automatic shutdown, then charge to 100% without interruption. After that cycle, the fuel gauge tracks the actual voltage cliff correctly and shutdown aligns with low single-digit percentages.