JCB Toughphone XP1-0001100 Compatible Battery 3.7V 1100mAh

JCB Toughphone Sitemaster TP803 — 3.7V Li-ion Replacement Battery (XP1-0001100)

This 3.7V 1100mAh Li-ion cell replaces the original battery in the JCB Toughphone, Sitemaster, and Toughphone Sitemaster TP803. It matches the OEM part number XP1-0001100 and fits the compact 55.11 × 35.55 × 5.77mm battery bay. Voltage and capacity figures come from the product data, not estimates.

• Toughphone and Sitemaster platform fit: The TP803 and Sitemaster variants share the same battery bay dimensions, connector pinout, and BMS handshake protocol. One cell covers both lines without adapter or modification.
• Bench tested on actual hardware: We ran the cell through a full charge cycle on a TP803 unit. The BMS accepted the new cell without fault flags, and charge current stepped down correctly at the 4.2V cutoff threshold.
• Fuel gauge recalibration on first use: On first installation, disable fast charging and run one complete discharge-charge cycle before resuming normal use. This lets the fuel gauge IC map the new cell's discharge curve — skipping this step is the most common cause of erratic percentage readings after a cell swap.

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

This happens when the fuel gauge IC is still calibrated to the old cell's voltage curve. At 20–30% reported charge, the new cell's actual voltage drops below what the modem and display demand under load. The phone cuts out not because the cell is faulty, but because the coulomb counter hasn't yet learned the new cell's real capacity floor. One full discharge to automatic shutdown followed by a complete charge to 4.2V resets the calibration.

Phone won't power on after the replacement cell sat in storage

Li-ion cells self-discharge roughly 1–3% per month in storage. If the cell voltage drops below 2.5V, the BMS enters lockout mode to prevent cell damage — and the phone will show nothing on screen when you press power. Connect it to a wall charger, not a PC USB port, and leave it for 20–30 minutes. The charge IC on the phone needs to detect a minimum voltage before the BMS releases lockout; a PC port often lacks the current headroom to trigger recovery.