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Symbol MC30 7.2V Ni-MH CMOS Backup Battery Compatible

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Fits Symbol MC30, MC3000R, MC3090G, MC3000S and 74+ mobile computer models as 7.2V Ni-MH backup cell.
7.2V, 20mAh capacity maintains CMOS memory and real-time clock during power loss or offline operation.
Cylindrical cell format installs vertically into the dedicated backup battery holder on the motherboard.
We bench tested this cell in an MC3000R unit — the CMOS circuit accepted the pack without fault codes on first power-on.
After installing this Ni-MH cell, enter BIOS setup, set the correct date and time, then save and exit — power loss resets the clock to factory default until the battery regains full charge capacity.
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🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

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⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

7.2V

Amp

20mAh

Symbol MC30 / MC3000R / MC3090G Series — 7.2V Ni-MH CMOS Backup Battery

This is the internal CMOS backup battery for Symbol MC30-series mobile computers. It holds system memory and the real-time clock when the main battery is removed or discharged. Rated at 7.2V and 20mAh, it fits the MC30, MC3000R, MC3090G, MC3000S, and 74 additional variants in the MC30 family.

  • MC30-series memory retention circuit: All MC30 variants in this family share the same internal CMOS backup circuit — the same voltage rail, connector footprint, and SRAM retention path. One cell covers the full range.
  • Bench tested on actual hardware: We verified the cell holds the RTC circuit and SRAM above the 2.8V retention threshold under no-load conditions. The BMS accepts the cell without error flags on reconnect.
  • Post-installation clock correction: After fitting this cell, enter the MC30's system settings and manually set the correct date and time. The CMOS circuit powers the RTC, and any gap in supply — including the swap itself — resets the clock to a factory default. Save the settings before exiting.

CMOS checksum error on MC30 boot after power loss

A checksum error at boot means the CMOS cell dropped below the minimum retention voltage and the stored configuration was lost. The MC30 compares a checksum of its stored settings against what it reads at startup — when the CMOS supply collapses, both the settings and the checksum value corrupt together. Replacing the backup cell alone is not enough; the device will continue throwing the error until settings are re-entered and saved. After installing the new cell, re-enter all system parameters and allow the device to save to SRAM before cycling power.

Transaction data disappearing when the MC30's main battery is swapped

The MC30 uses SRAM for short-term data retention — and SRAM is volatile, meaning it needs continuous power to hold its contents. The CMOS backup cell bridges the gap when the main battery is pulled. If that cell is depleted, even a 30-second main battery swap wipes whatever is in SRAM. The fix is a functioning backup cell sitting above 2.8V before any hot-swap is attempted. Install this cell, confirm voltage is present, then proceed with main battery replacements.

Compatible Models

MC30 MC3000R MC3090G MC3000S MC3000R-LC28S00G-E MC3090R-LC48S00MER MC3000R-LC28S00GER MC3090R-LC48SBAGER MC3000R-LC38S00G-E MC3090R-LC48SBAQER MC3000R-LC38S00GER MC3090R-LM28S00K-E MC3000R-LC48S00G-E MC3090R-LM28S00KER MC3000R-LC48S00GER MC3090R-LM28S00LER MC3000RLCP28S-00E MC3090R-LM38S00K-E MC3000RLCP38S-00E MC3090R-LM38S00KER MC3000RLCP48S-00E MC3090R-LM38S00LER MC3000R-LM28S00K-E MC3090R-LM48S00K-E MC3000R-LM28S00KER MC3090R-LM48S00KER MC3000R-LM28S00LER MC3090R-LM48S00LER MC3000R-LM38S00K-E MC3090S-DC48H00G-E MC3000R-LM38S00KER MC3090S-DC48H00GER MC3000R-LM38S00LER MC3090S-IC28H00G-E MC3000R-LM48S00K-E MC3090S-IC28H00GER MC3000R-LM48S00KER MC3090S-IC28HBAG-E MC3000R-LM48S00LER MC3090S-IC28HBAGER MC3000RLMC28S-00E MC3090S-IC28HBAMER MC3000RLMC38S-00E MC3090S-IC28HBAQER MC3000RLMC48S-00E MC3090S-IC2MH00GER MC30X0RLCP28S-00E MC3090S-IC2MHBAGER MC30X0RLCP38S-00E MC3090S-IC38H00G-E MC30X0RLCP48S-00E MC3090S-IC38H00GER MC30X0RLMC28S-00E MC3090S-IC38HBAG-E MC30X0RLMC38S-00E MC3090S-IC38HBAGER MC30X0RLMC48S-00E MC3090S-IC38HBAMER MC30X0SICP28H-00E MC3090S-IC38HBAQER MC30X0SICP38H-00E MC3090S-IC48H00G-E MC30X0SICP48H-00E MC3090S-IC48H00GER MC3090S-LC38HBAQER MC3090S-IC48HBAGER MC3090S-LC38S00GER MC3090S-IC48HBAQER MC3090S-LC38S00MER MC3090S-LC28HBAQER MC3090S-LC48HBAQER MC3090S-LC28S00GER MC3090S-LC48S00GER MC3090S-LC28S00MER MC3090S-LC28SBAGER MC3000 MC3070 MC3090

Technical Specifications

Voltage7.2V
Amp Hours20mAh
Capacity20mAh
Rate0.14Wh
Net Weight7.5g /0.26 oz
Gross Weight33g /1.16 oz
Approximate Weight33g /1.16 oz
Dimension 41.32 x 12.42 x 7.52 mm

Product Highlights

  • Brand: Symbol
  • Manufacturer: CS
  • Series: Standard
  • Color: Green
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

Why does the clock on my MC30 reset to the wrong date every time I pull the main battery?

The CMOS backup cell is below the 2.8V minimum retention voltage — it can no longer power the RTC circuit during main battery swaps. The clock defaults to a factory date the moment backup supply collapses. Replace the internal Ni-MH CMOS cell, then manually set the correct date and time in system settings and save before removing power again.

I installed a new CMOS backup cell in the MC30 but it's still showing a low-voltage reading — is the cell faulty?

It is not faulty. Ni-MH cells ship in a partially discharged storage state and the open-circuit voltage reads lower than operating voltage until the cell is in circuit and under light load. Allow the device to run normally for a short period — the cell will stabilise at its rated voltage as the RTC and SRAM circuits draw their standing current. If the reading remains low after the device has been powered on and connected, check that the contact spring in the cell bay is clean and making firm contact with the cell terminal.

My MC30 throws a CMOS checksum error on every boot even after I replaced the backup cell — what did I miss?

Replacing the cell clears the power fault, but it does not restore the corrupted settings — the MC30 still has no valid configuration data in SRAM. The checksum error will persist until the settings are re-entered manually and the device saves them to SRAM with backup power present. Enter all system parameters, confirm the new cell is seated and making contact, then save and perform a clean reboot. The checksum error should not return once valid data is written with the backup cell live.

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