About this replacement
Symbol MC50 Series — 1.2V Ni-MH CMOS Backup Battery (106)
This is a 1.2V 20mAh Ni-MH backup battery for the Symbol MC50 series mobile computer. It maintains SRAM contents and the real-time clock circuit during main battery swaps or full power loss. Compatible with MC50, MC5040, MC5040-PK0DBNEA72R, MC5040-PK0DBNEA7WR, and 17 additional MC50 variants.
- MC50 series fit: All listed MC50 variants share the same CMOS backup circuit, connector footprint, and 1.2V retention voltage rail. The BMS handshake here is passive — this cell feeds the RTC and SRAM directly with no active management layer between them.
- Bench tested on actual hardware: We ran this cell against the MC50 CMOS circuit and confirmed stable voltage delivery to the RTC module. The cell held retention voltage above the 1.0V minimum threshold throughout the test cycle without dropout.
- Post-install RTC correction: After fitting this cell, power on the MC50 and manually set the correct date and time in the device settings. The CMOS circuit powers the RTC, and any gap in backup power resets the clock to its factory default — it will not self-correct after the swap.
SRAM data loss every time the main battery is removed
The MC50 uses this Ni-MH cell to keep SRAM alive during main battery swaps. When the backup cell drops below its retention floor, SRAM loses power the instant the main pack is disconnected. Stored settings, session data, and clock values reset immediately. A fresh cell restores the bridge — SRAM stays live through the swap window as intended.
Clock resets to a default date after every full power cycle
This symptom points to the backup cell being fully depleted — not just low. When the cell can no longer sustain the RTC circuit through a power-off event, the clock reverts to its factory epoch on every boot. A depleted Ni-MH cell in this role typically reads well below 1.0V under load. Replace the cell, then set the correct date and time manually before putting the unit back into service.