About this replacement
Unitech PA550 — 3.7V Li-ion Replacement Battery (1400-900008G)
This is a 3.7V, 2200mAh Li-ion replacement battery for the Unitech PA550 handheld barcode scanner. It fits the PA550 directly using OEM part number 1400-900008G. The PA550 is a handheld data collection device used in retail, logistics, and warehouse environments.
- PA550 platform fit: The PA550 runs a single-cell Li-ion rail at 3.7V nominal. This pack matches that voltage rail, the physical footprint, and the BMS communication protocol the PA550 expects on power-up — the device will not initialise with a mismatched pack.
- Bench tested on actual hardware: We cycled this pack through simulated scan-burst loads on the PA550 platform. The BMS held charge cutoff correctly at full cell voltage and triggered low-voltage protection before cell damage could occur on deep discharge.
- First-shift preparation for pick-and-pack use: After installing, place the scanner in its cradle for a full charge cycle before putting it into service. Scan trigger inrush current is highest when the cell is near minimum charge — starting a shift on a fully charged cell prevents false BMS trips when the trigger fires repeatedly in rapid succession.
Cradle showing a charging error on a new pack
The PA550 cradle communicates with the battery pack through gold-plated contact pins on the base of the device. If those contacts are dirty or oxidised, the dock reads elevated resistance and flags a charging fault — even with a fully functional new pack seated correctly. Wipe the pack contacts and the cradle pins with a dry lint-free cloth, then reseat the unit firmly. If the error clears within 30 seconds of reseating, contact resistance was the cause, not the battery itself.
Scanner losing wireless connection during rapid scan bursts
On the PA550, the wireless radio and the scan trigger draw current simultaneously during a rapid scanning sequence. If the cell voltage sags below the radio module's minimum operating threshold mid-burst, the wireless stack drops its connection before the BMS cuts power entirely. This is more likely on a partially charged pack or one that has been cycled heavily. Starting each shift with the pack charged to at least 3.9V keeps enough headroom above the radio module's dropout point to sustain both loads through a continuous scan burst.