PK07100 HTC J Z321e Replacement Battery 3.8V 1950mAh

HTC J Z321e / ISW13HT — 3.8V Li-ion Replacement Battery (PK07100)

This 3.8V, 1950mAh Li-ion cell replaces the original battery in the HTC J Z321e, J ISW13HT, and Nippon variants. It powers the processor, display, and cellular radio stack. OEM part numbers PK07100, 35H00189-00M, 35H00189-02M, and HTI13UAA all cross to this cell.

• J Z321e and ISW13HT platform fit: Both handsets share the same battery bay geometry, connector pinout, and BMS handshake protocol — one cell covers the full variant range without modification.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the J Z321e platform. The BMS accepted charge current cleanly, thermistor communication stayed active throughout, and the protection circuit tripped correctly at low-voltage cutoff.
• Fuel gauge recalibration on first install: On first use after installation, disable fast charging and run one complete discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before fast charge current is applied to an uncalibrated cell.

Sudden shutdown at 20–30% on the HTC J Z321e after a cell swap

This happens because the fuel gauge IC is still running the discharge curve it learned from the old, degraded cell. The new cell has a steeper voltage cliff under modem and display load than the IC expects. When current draw spikes — during a call, a data burst, or screen-on activity — cell voltage drops briefly below the protection threshold even though the reported percentage says 25%. One full discharge cycle, letting the phone reach 1% naturally before recharging, forces the coulomb counter to re-anchor to the new cell's actual voltage profile.

Phone warm near the battery bay on the first few charges after replacement

A new cell starts with higher internal impedance than a broken-in one. The charge IC pushes the same current it used on the old cell, but higher impedance means more energy converts to heat at the cell terminals. This is normal and settles after three to five cycles as the cell's internal resistance drops. If warmth continues past five full cycles or the phone feels hot rather than warm, check that the thermistor tab is seated flat against the cell — a lifted thermistor causes the charge IC to misread cell temperature and run charge current too aggressively.