Symbol WT4000 Replacement Battery 3.7V 2200mAh Li-ion

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

This 3.7V, 2200mAh Li-ion battery replaces the original pack in the Symbol WT4000, WT4090, WT4090i, and WT41N0 wearable mobile computers. These are wrist-mounted barcode scanners used in warehouse pick-and-pack, retail, and field service workflows. OEM part numbers covered include 55-000166-01, BTRY-WT40IAB0E, BTRY-WT40IAB0H, 82-90005-05, and 82-90005-03.

• WT4000 and WT41N0 platform fit: These models share the same battery bay geometry, connector pinout, and BMS handshake protocol. The WT41N0 added 802.11n radio support, but the power rail and pack interface remain identical to the WT4000 — one battery spec covers the full range.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a WT4090 and monitored the BMS response during scan-trigger inrush events. Cell voltage held stable and the BMS did not trip at low state-of-charge under repeated laser activation bursts.
• First-shift charge protocol: After installing, place the scanner in its cradle for a full charge cycle before starting a picking shift. Scan-trigger inrush current is at its peak when the cell is near minimum — a fully charged cell prevents false BMS trips that can look like a faulty battery on the first shift.

Cradle showing charging error on a new pack

The WT4000 series cradle reads battery state through four contact pads on the pack's underside. Oxidation or residue on those pads raises contact resistance, which the dock interprets as a fault rather than a low battery. Wipe both the pack contacts and the cradle contacts with a dry cloth, then reseat the scanner firmly until you hear the click. If the error clears within 30 seconds of reseating, the contacts were the cause — not the pack or the charger.

Scanner losing wireless connection during rapid scan bursts

On the WT41N0 especially, simultaneous 802.11n polling and scan-trigger activation create a combined inrush draw that can momentarily sag cell voltage below the radio module's minimum threshold. When that happens, the wireless stack drops and must re-associate — which shows up as a connection loss rather than a battery warning. This is most common when the pack is below 20% charge. Keeping the pack above that level during active picking shifts eliminates most mid-burst drop-outs; check cell voltage at the device status screen — anything below 3.55V under load warrants a swap.