About this replacement
Symbol SPT-1500 / SPT-1550 — 2.4V Ni-MH Replacement Battery (21-42921-01)
This is a 2.4V, 700mAh Ni-MH replacement battery for the Symbol SPT-1500 and SPT-1550 handheld barcode scanners. It replaces OEM part numbers 21-42921-01 and BTRY-MC90SAB00-01. If your scanner is cutting out mid-shift or failing to hold a charge, this pack is the direct swap.
- SPT-1500 and SPT-1550 compatibility: Both models run the same 2.4V battery rail, use the same physical housing dimensions, and share the same BMS handshake protocol — one part number covers both. No adapter or firmware change needed.
- Bench tested on actual hardware: We cycled this pack through repeated scan-burst sequences and monitored BMS cutoff thresholds. The cell held within expected voltage tolerance under combined laser trigger and radio transmission draw.
- First-shift prep for pick-and-pack operations: After installing, seat the scanner in its charging cradle for a full charge cycle before using it on the floor. Scan trigger inrush current is at its highest when the cell is near minimum — a fully charged cell prevents false BMS trips during the opening burst of a busy shift.
Cradle showing a charging error on a freshly installed pack
A charging error on a new pack is almost always a contact resistance issue, not a fault with the battery itself. Ni-MH cells can arrive with a surface oxide layer on the terminals that raises resistance enough to trigger the dock's error state. Wipe the gold contacts on both the battery pack and the cradle slot with a dry cloth, then reseat the pack firmly until it clicks. If the error clears, the dock is reading the pack correctly and the charge cycle will proceed normally.
Scanner drops wireless connection during rapid back-to-back scanning
The SPT-1500 fires both the scan laser and the wireless radio in close succession during fast barcode sequences. At low cell charge, the combined inrush from both draws can pull the pack voltage below the BMS protection floor, causing a momentary shutdown that the scanner reports as a connection drop. This is not a radio fault — it is a voltage sag event. Recharge the pack to full before a high-frequency scanning session and the drops will stop.