T-Mobile Shadow 3.7V Replacement Battery 35H00102-00M

T-Mobile Shadow Series — 3.7V Li-ion Replacement Battery (35H00102-00M)

This 3.7V, 950mAh Li-ion cell replaces the original battery in the T-Mobile Shadow, Shadow Copper, and Copper Sage. The original OEM part numbers are 35H00102-00M and KII0160. When the stock cell degrades and the phone no longer holds a usable charge, this unit slots in as a direct swap.

• Shadow, Shadow Copper, and Copper Sage compatibility: All three variants share the same battery bay dimensions, connector pinout, and 3.7V voltage rail. The BMS handshake protocol is identical across the lineup, so one cell covers all three without modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on the Shadow platform. The BMS accepted the cell without error flags, and the charge IC stepped through trickle, bulk, and termination phases correctly.
• Fuel gauge recalibration on first use: After installation, run one complete discharge down to auto-shutoff, then charge uninterrupted to 100%. This gives the fuel gauge IC a clean reference curve against the new cell — skip this step and the percentage readout will be off from day one.

Sudden shutdown at 20–30% on the T-Mobile Shadow after a cell swap

The Shadow's fuel gauge IC was calibrated to the discharge curve of the original aged cell. A fresh cell holds a higher voltage at low state-of-charge than the worn cell the IC was trained on. When load spikes from the radio stack or display hit, the IC sees a voltage drop it interprets as empty and triggers a shutdown — even though capacity remains. One full discharge-to-shutoff cycle followed by a full charge resets the coulomb counter against the new cell's actual curve and eliminates this behaviour.

Phone shows incorrect battery percentage after replacement cell installed

The fuel gauge IC on the Shadow stores a learned discharge curve from the previous cell. A new 950mAh cell with lower internal impedance reports different voltage at each charge level than the old degraded unit. The IC maps those voltage readings to percentage using the old curve, so the number on screen drifts — often reading 80% then jumping to 95%, or dropping from 40% straight to 5%. Force a full charge to 100% without interruption, then drain fully to auto-shutoff, and the IC will recalibrate to 3.7V nominal at the correct reference points.