Panasonic Toughbook CF-T5 CMOS Battery 3V 200mAh Lithium

Panasonic Toughbook CF-T5 / CF-30 / CF-T8 / CF-H1 — 3V Lithium CMOS Backup Battery

This is a 3V lithium coin cell replacement for the CMOS/RTC circuit on Panasonic Toughbook laptops, including the CF-T5, CF-30, CF-T8, and CF-H1. It maintains BIOS settings and real-time clock function when the main battery is removed or the unit loses mains power. Capacity is 200mAh (0.6Wh) and dimensions are 20 × 20 × 3.8mm.

• Multi-model Toughbook fit: The CF-T5, CF-30, CF-T8, and CF-H1 share a common CMOS circuit layout and connector footprint that accepts this 20mm cell format. The RTC and SRAM on each platform draw from the same 3V retention rail, so one cell specification covers all listed models.
• Bench tested on actual hardware: We verified open-circuit voltage at 3.0V and confirmed the cell holds retention voltage above the 2.8V minimum threshold that the CMOS circuit requires to preserve stored settings. BIOS and clock data remained intact across power interruptions during testing.
• Post-install BIOS step for Toughbook RTC: After fitting this cell, enter the BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a default value during the swap — it does not auto-correct from an NTP server until the OS boots and network connects, so correcting it in BIOS first prevents timestamp errors in logged field data.

BIOS clock resetting to 2000 after every power cycle

When the Toughbook CMOS cell drops below 2.8V, the RTC circuit loses its reference voltage and defaults the clock to January 1, 2000 on every cold boot. This happens even if the main battery is healthy — the CMOS cell is a separate circuit that runs independently. The symptom gets worse as the cell ages because self-discharge accelerates once capacity falls below 50%. Replace the cell and set the correct date in BIOS; confirm the cell reads at or above 3.0V with a multimeter before fitting.

CMOS checksum error on boot after fitting a new cell

A checksum error immediately after a new coin cell install usually means the BIOS lost its stored configuration during the swap and is now comparing blank SRAM against a saved checksum that no longer matches. This is expected behaviour — it does not mean the new cell is faulty. Enter BIOS setup, reload default settings, then re-enter any custom configuration values and save. If the error persists across reboots with a confirmed 3.0V cell, inspect the motherboard contact spring for corrosion or flattening from the previous cell.