About this replacement
Sonel KT-670 / KT-640 / KT-560 — 10.8V Li-ion Replacement Battery (WAAKU18)
This is a 10.8V, 2600mAh Li-ion replacement battery for the Sonel KT-670, KT-640, and KT-560 thermal cameras. It replaces OEM part number WAAKU18 and uses the same connector and BMS communication protocol as the original pack. Capacity is rated at 28.08Wh, matching factory specification.
- KT-670, KT-640, KT-560 compatibility: These three Sonel thermal camera models share the same 10.8V battery rail, physical form factor, and BMS handshake. The same WAAKU18 pack runs across all three without any modification to the camera or charging contacts.
- Bench tested on actual hardware: We cycled this pack through full charge and discharge sequences while monitoring BMS cutoff thresholds. The protection circuit responded correctly to over-discharge and thermal stress events, and the charge controller accepted the pack without fault codes.
- Post-storage power-on procedure: If the camera has been stored with this battery installed and discharged below 3V per cell, the BMS may enter deep-discharge lockout. Connect the battery to the Sonel charger for at least 15 minutes before attempting to power on the camera — do not insert a deeply discharged pack into the camera and press the power button as the first step.
Sonel KT-670 shutting down mid-inspection on a freshly charged battery
The KT-670 combines a display backlight, an IR detector array, and a continuous detector heating element — all drawing current simultaneously. Under this combined load, the BMS can trip a protection cutoff if cell voltage sags below the cutoff threshold, even when the battery indicator shows adequate charge. This is more likely in cold environments where internal cell resistance rises and voltage sag deepens under the same current draw. A battery with aged cells will hit this threshold sooner than a new pack with healthy cells. If the camera shuts down unexpectedly, check that the battery rests at 12.6V on a multimeter before reinserting — anything below 11.5V at rest suggests a weak pack.
Thermal image accuracy degrading before the low-battery indicator appears
The KT-670's IR detector requires stable voltage for accurate temperature readings — the detector's gain calibration is voltage-sensitive, and as the pack discharges toward its lower range, small voltage fluctuations affect the signal baseline. The battery indicator on the camera reads state of charge from a fuel gauge IC, which can lag behind actual cell voltage under load. This means the display may still show one or two bars while the detector is already operating outside its calibrated voltage window, producing temperature readings that drift by 1–3°C. If field readings appear inconsistent late in a charge cycle, swap the battery and re-run the camera's flat-field correction sequence from the settings menu before continuing the inspection.