Extech i5 Thermal Camera Replacement Battery 3.7V 3400mAh

Extech i5 Infrared Camera — 3.7V Li-ion Replacement Battery (1950986)

This 3.7V, 3400mAh Li-ion battery replaces the original power cell in the Extech i5 Infrared Camera and the Flir i7. It restores full operation to compact thermal imaging cameras used in building diagnostics, electrical panel inspections, and HVAC fault finding. Capacity figure is taken directly from product data at 12.58Wh.

• i5 and Flir i7 platform fit: Both cameras share the same 3.7V cell format, physical dimensions, and connector pinout. The BMS handshake on each model expects the same charge termination voltage, so one cell covers both without modification.
• Bench tested on actual hardware: We cycled this cell through the combined load of the thermal detector's heating element and the LCD display on an i5 body. The BMS held stable discharge down to the cutoff threshold with no premature trip under typical inspection load.
• Post-install warm-up on the i5: After fitting a new battery and powering on, let the camera run undisturbed for at least 60 seconds before taking any thermal readings. The uncooled microbolometer detector needs the internal electronics to reach a stable temperature baseline — measurements taken before that point will show calibration drift.

Thermal camera shutting down mid-inspection on a new battery

The i5 draws current from two simultaneous loads: the resistive heating element that keeps the microbolometer at operating temperature, and the backlit LCD. Together, these can pull a brief current spike that the BMS reads as an overload condition, triggering a protection cutoff. This is more likely if the battery has been sitting at a partial state of charge before installation. A full charge cycle to 4.2V before first use resets the cell's state-of-charge register and lets the BMS calibrate its current thresholds correctly. If shutdowns persist, check that the battery contacts on the camera body are clean and making full metal-to-metal contact.

Thermal readings drifting before the battery indicator shows low

The microbolometer in the i5 is voltage-sensitive — thermal accuracy begins to degrade when cell voltage drops below roughly 3.5V, even though the camera's battery gauge may still show one or two bars. The display and detector heating element continue functioning at that voltage, so the device appears operational while the sensor output loses accuracy. If your readings show unexpected hot or cold patches that disappear after a fresh charge, the cell voltage under load is the likely cause. Recharge the battery and trigger a manual flat-field correction (the shutter-click recalibration) immediately after power-on before resuming the inspection.