ONeil PB20A Microflash 4i Replacement Battery 7.4V 3400mAh

ONeil Microflash 4i Series — 7.4V Li-ion Replacement Battery (PB20A)

This 7.4V, 3400mAh Li-ion battery replaces the OEM pack in the ONeil Microflash 4i, 4tCR, 4T Printer, and related 4T-series portable barcode scanners. These handheld units are common in warehouse pick-and-pack, retail stockrooms, and logistics operations where scanners run continuously across full shifts. OEM part numbers covered include PB20A, PB40, PB41, PW40, and 550034-000 among others.

• Microflash 4-series compatibility: The 4i, 4tCR, 4T Printer, and related models share the same 7.4V power rail, physical form factor, and BMS handshake protocol. One cell fits all of them without modification to the bay or firmware.
• Bench tested on actual hardware: We ran this pack through scan-burst cycling on the Microflash platform and confirmed the BMS holds voltage above the scanner's minimum threshold during combined laser trigger and wireless radio draw. No false cutoffs were observed across repeated rapid-scan sequences.
• First-shift prep on the cradle: After installing, place the scanner in its charging cradle for a full charge cycle before deploying it on the floor. Scan trigger inrush current is highest when the cell is near minimum, and starting the first shift on a fully charged pack prevents BMS trips during the initial high-demand period.

Cradle showing a charging error on a brand-new pack

Charging docks on the Microflash series communicate pack status through spring-loaded contacts on the base of the scanner. Oxidation, dust, or residue on either the pack or cradle contacts interrupts the handshake and triggers a fault light before any charge current flows. Wipe the contacts on both the battery and the dock with a dry lint-free cloth, then reseat the scanner firmly until the dock clicks. If the error clears within 30 seconds, contact resistance was the cause — not a faulty cell.

Scanner losing wireless connection during a rapid scan burst

The Microflash 4-series draws from the same cell for both the scan trigger and the wireless radio simultaneously. During a rapid burst of back-to-back scans, combined inrush current can cause a momentary voltage sag that drops the radio below its minimum operating threshold. This shows up as a mid-session wireless dropout rather than a full power-off. If this happens, check cell voltage under load — a healthy 7.4V pack should hold above 6.8V during burst scan activity.