About this replacement
HP Armada M300 / M700 / E500 — 3V Lithium CMOS Backup Battery (152605-003)
This is a 3V, 200mAh lithium coin cell replacement for the CMOS/RTC circuit on HP Armada M300, M700, E500, EVO N600C, and compatible notebooks. It carries OEM part number 152605-003 and maintains BIOS settings, system clock, and stored configuration when the laptop is off or unplugged. When this cell drops below the retention threshold, the board loses all stored state on every power cycle.
- Armada and EVO N-series compatibility: These notebooks share a common RTC circuit and connector footprint across the M300, M700, E500, and EVO N600C lines. The same CMOS cell backs the SRAM and powers the real-time clock oscillator across all listed models.
- Bench tested on actual hardware: We checked open-circuit voltage before shipping and confirmed the BMS contacts pass current correctly through the retention circuit. The cell held stable output at the RTC rail without voltage sag under low-draw standby load.
- Post-installation clock reset: After fitting the new cell, enter BIOS immediately and set the correct date and time, then save and exit. The RTC circuit resets to a factory default the moment the old cell is removed — the new cell holds whatever value the BIOS writes, but it cannot recover the previous setting on its own.
BIOS clock resetting to 2000 after every power cycle
The Armada RTC circuit requires a minimum of 2.8V from the CMOS cell to retain date, time, and stored settings. A depleted cell falls below this threshold the moment mains power is removed, and the clock defaults to January 1, 2000 on every cold boot. This is not a BIOS fault — it is the SRAM losing state because the backup voltage rail collapses. Replacing the 152605-003 cell and then saving the correct date in BIOS resolves this immediately.
CMOS checksum error on boot with no other changes made
A checksum error on the Armada boot screen means the CMOS cell has fully discharged and the stored configuration — including boot order, memory timings, and system settings — no longer matches the checksum the BIOS recorded. The board detects the mismatch and halts to warn you before loading defaults. Fitting a fresh 152605-003 cell is the first step; after that, re-enter all BIOS settings manually and save. If the error returns after replacement, inspect the coin cell contact spring on the motherboard for oxidation or physical damage preventing solid electrical contact.