Cricket WTCKT01 Replacement Battery 3.85V 4000mAh JU001

Cricket WTCKT01 / Icon 4 — 3.85V Li-Polymer Replacement Battery (JU001)

This is a 3.85V, 4000mAh lithium-polymer cell replacing part number JU001 in the Cricket WTCKT01 and Icon 4 smartphones. It matches the original voltage, capacity, and connector pinout. Install it when the original cell no longer holds charge through a normal day of use.

• WTCKT01 and Icon 4 fitment: Both devices share the same battery bay dimensions, connector layout, and BMS handshake protocol. This cell measures 80.00 × 65.30 × 4.60mm and seats flush in either model without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Cricket Icon 4 unit. The onboard charge IC accepted the cell without fault codes, and the BMS reported state-of-charge correctly after one full cycle.
• Fuel gauge recalibration 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 the new cell's discharge curve before high-current charging pushes current into an uncalibrated state — preventing erratic percentage jumps later.

Sudden shutdown at 20–30% on the WTCKT01 after a cell swap

A new lithium-polymer cell has a slightly different voltage-versus-capacity curve than the aged cell the fuel gauge IC was trained on. When the phone's modem fires a high-current burst — during a call or LTE handoff — voltage sags below the protection threshold before the display percentage reaches zero. The BMS trips and the phone shuts off, even though the gauge still reads 20–30%. One full discharge-charge cycle at standard rate recalibrates the coulomb counter and pushes the cutoff point back to where it belongs.

Phone not powering on after the replacement cell sat in storage

Lithium-polymer cells self-discharge during storage. If the cell dropped below 2.5V per cell, the BMS enters lockout mode to prevent damage and the phone will not respond to the power button. Connect the phone to a 5V wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing anything. The charge IC trickle-charges the cell back above the BMS re-enable threshold, typically around 2.9V, at which point normal charging resumes and the phone will power on.