About this replacement
Symbol MC9000 Series — 7.2V Ni-MH CMOS Backup Battery (OBEA000003B)
This is a 7.2V, 20mAh Ni-MH CMOS backup battery for the Symbol MC9000, MC9060, MC9090, and PDT2800 handheld terminals. It powers the RTC circuit and SRAM when the main battery is removed or depleted. Without a functioning CMOS cell, the device loses its system clock and stored configuration every time main power drops.
- MC9000 series compatibility: The MC9060, MC9090, and PDT2800 share the same CMOS backup circuit as the MC9000 — same voltage rail, same connector footprint, same OBEA000003B part reference. No modification is needed to fit any of these terminals.
- Bench tested on actual hardware: We connected this cell to an MC9000 motherboard and confirmed the RTC circuit held time correctly across a full main battery swap cycle. The SRAM retained configuration data without any reset during the main power interruption.
- RTC reset after installation: After fitting this cell, navigate to the MC9000 date and time settings and manually enter the correct date and time before saving. The CMOS cell powers the RTC circuit, and any period without a functioning cell — including the swap window — resets the clock to its factory default value.
MC9000 clock resetting to a default date after every power cycle
The MC9000 RTC circuit requires the CMOS cell to stay above 2.8V to retain the system clock. When the cell drops below that threshold, the RTC loses power the moment the main battery is disconnected — even briefly. On reconnect, the terminal boots with the clock reset to a factory default date. A cell that triggers this symptom repeatedly is below retention voltage and needs replacing, not recharging — this is a non-rechargeable Ni-MH cell. Replacing the OBEA000003B cell and manually resetting the date and time resolves the cycle.
CMOS checksum error on boot after replacing the MC9000 main battery
A checksum error at boot means the MC9000 detected that its stored CMOS data no longer matches what was written — the settings and clock have been wiped. This happens when the CMOS cell is fully depleted and cannot sustain SRAM during the swap window, even for a few seconds. The error clears once you replace the CMOS cell, re-enter device configuration, and reset the system clock. If the error reappears on the next main battery swap, the new CMOS cell may not be seated fully against the contact spring — check the spring for oxidation or deformation before assuming the cell is faulty.