UTStarcom BTR1400 CDM-1400 Replacement Battery 3.7V 600mAh

UTStarcom CDM-1400 / PCS-1400 — 3.7V Li-ion Replacement Battery (BTR1400)

This is a 3.7V, 600mAh Li-ion cell replacing the original BTR1400 battery in the UTStarcom CDM-1400, PCS-1400, PPC-1400, and PPC-1400 Slice handsets. These are early 2000s candybar-style phones with a compact battery bay and a simple charge IC. When the original cell degrades, the phone shuts down unexpectedly or refuses to hold a charge — this cell restores normal operation.

• CDM-1400 / PCS-1400 / PPC-1400 platform fit: All listed models share the same 3.7V single-cell architecture, identical connector pinout, and the same BTR1400 form factor — 37.40 × 37.00 × 6.00mm. The BMS handshake is passive on these devices, so there is no proprietary authentication challenge to pass.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the CDM-1400 platform. The BMS held charge termination correctly at full voltage and did not trip on normal screen-and-call load draws.
• Fuel gauge recalibration on first cycle: After fitting this cell, run one full discharge down to auto-shutoff, then charge uninterrupted to 100%. The phone's fuel gauge IC was calibrated to the old cell's discharge curve — skipping this step causes the percentage display to jump or read incorrectly for the first several cycles.

Why the CDM-1400 reports wrong battery percentage after a cell swap

The CDM-1400 uses a basic coulomb-counting fuel gauge IC that tracks charge by comparing against a stored discharge curve from the previous cell. A new cell has a different internal impedance profile, so the IC's stored reference no longer matches reality. The percentage shown on screen can read 40% while the actual cell voltage is already near cutoff. One full discharge-to-shutoff and uninterrupted recharge resets the reference point the IC uses for all future readings.

Sudden shutdown at 20–30% on the CDM-1400

This happens when the cell voltage drops sharply under load — a behaviour called a voltage cliff. During a call, the modem and screen draw current simultaneously, pulling the cell below the BMS cutoff threshold even though the gauge still shows charge remaining. On a fresh replacement cell, this usually means the fuel gauge IC has not yet recalibrated and is reporting an inflated percentage. After one full discharge cycle, verify the phone does not shut off above 3.4V under call load — if it does, the cell itself may have been stored below 2.5V and needs a slow trickle charge to recover.