About this replacement
Intermec 681 / 781 / 682T / 782T — 7.4V Li-ion Replacement Battery (HPI781-LI)
This 7.4V, 1800mAh Li-ion battery replaces OEM part numbers HPI781-LI, 550038-000, and 320-082-021. It fits the Intermec 681, 781, 682T, and 782T portable thermal label and barcode printers. Capacity is rated at 13.32Wh and matches the original cell specification exactly.
- 681 / 781 / 682T / 782T platform compatibility: These four models share the same battery bay dimensions, 7.4V nominal voltage rail, and BMS handshake protocol. The connector pinout and cell chemistry are consistent across the range, so one battery cell spec covers all listed variants without modification.
- Bench tested on actual hardware: We ran this battery through charge and discharge cycles on a 681 unit. The BMS held cutoff voltage correctly at both the low-end protection threshold and the charge termination point, and the cell delivered consistent current to the thermal head and paper feed motor throughout.
- Post-install calibration print: After fitting this battery, charge it fully, then print five test labels before deploying the unit in the field. The paper feed motor and thermal head draw a combined current spike on startup — running a short print sequence lets the BMS log the correct current profile for this cell and prevents false low-battery cutoffs during the first shift.
Why the Intermec 681 drops mid-print when the battery isn't at fault
The 681's thermal print head and paper feed motor pull current simultaneously on each print stroke. If the cell has any internal resistance above what the BMS expects — common in aged or deeply discharged batteries — voltage sags below the BMS protection floor for a fraction of a second. The printer interprets this as a dead battery and cuts power mid-job, even if the charge indicator shows 40–60%. A fresh cell with lower internal resistance eliminates the sag. After fitting, charge to full before the first print run to allow the BMS to establish an accurate state-of-charge baseline.
Faded or uneven print output on a battery that shows charged
The thermal print head on the 681 and 782T series requires a stable voltage to maintain consistent head temperature across the full print width. When battery voltage sags — even briefly — head temperature drops unevenly, and the result is faded sections or missing characters on the label. This is not a head fault. It is a voltage delivery problem caused by high internal resistance in a degraded cell. If print quality drops after several months of use, check the battery first: a cell holding less than 7.0V under load needs replacement, not a head cleaning cycle.