Symbol WT4000 Barcode Scanner Replacement Battery 3.7V 4400mAh

Symbol WT4000 / WT41N0 Series — 3.7V Li-ion Replacement Battery (55-000166-01)

This 3.7V, 4400mAh Li-ion cell replaces the original pack in the Symbol WT4000, WT4090, WT4090i, and WT41N0 wrist-worn mobile computers. These units run in warehouse and retail environments where scan cycles run continuously across full shifts. The battery matches the OEM voltage rail and connector to fit without modification.

• WT4000 and WT41N0 platform compatibility: All models in this series share the same 3.7V battery bay, connector pinout, and BMS handshake protocol. Swapping between WT4090 and WT41N0 units uses the same pack — the charge controller reads cell state identically across all four variants.
• Bench tested on actual hardware: We ran this pack through the WT4000 charge cycle on a live cradle. The BMS accepted charge immediately, balanced cells within the first full cycle, and held voltage above 3.6V through sustained scan-burst loads without tripping the overcurrent cutoff.
• First-shift startup tip for pick-and-pack operations: After installing a new pack, seat the scanner in its cradle and let it complete a full charge before triggering a scan shift. The scan trigger plus active wireless radio creates the highest combined inrush current draw near minimum charge — a pre-charged cell prevents the BMS from tripping on that first pull of the day.

Why the WT4000 cradle shows a charging error on a new pack

The WT4000 four-slot cradle reads battery state through the dock contacts before starting the charge cycle. If those contacts have oxidation or debris — common on packs pulled from storage — the cradle throws a fault instead of initiating charge. The BMS on the pack is not the issue; contact resistance is. Wipe the gold contacts on the battery and the cradle slot with a dry cloth, reseat the pack firmly, and the charging indicator should flip to active within 30 seconds.

Scanner losing wireless connection during rapid scan bursts

During fast scan sequences, the WT4000 draws simultaneously from the imager, processor, and 802.11 radio. That combined inrush can pull the cell voltage below the radio's minimum threshold for a fraction of a second — enough for the wireless stack to drop association. A degraded or low-charge pack narrows the voltage headroom, making the drop more frequent. If disconnects happen consistently during scan bursts, charge the pack fully and retest; if the symptom persists above 3.6V resting voltage, the original cell has capacity fade and needs replacement.