Extech VIR50 Replacement Battery 3.7V 1600mAh BATT-37V

Extech VIR50 — 3.7V Li-ion Replacement Battery (BATT-37V)

This is a 3.7V Li-ion battery rated at 1600mAh (5.92Wh), built to replace the OEM BATT-37V pack in the Extech VIR50 infrared thermal camera. The VIR50 is a handheld imaging instrument used for building envelope diagnostics, electrical panel inspections, and HVAC system surveys. One cell in a compact 52.35 × 18.40 × 18.40mm form factor slots directly into the VIR50 battery bay.

• VIR50 compatibility: The VIR50 uses a single-cell 3.7V nominal pack with a passive protection circuit — no active BMS handshake to the host instrument. The BATT-37V footprint and connector orientation are specific to this camera body, so the physical fit is what matters most here.
• Bench tested on actual hardware: We cycled this pack through the VIR50's sensor-on load profile. The protection circuit held stable through thermal detector initialisation, which draws a short current spike above steady-state imaging load. No false cutoffs on startup.
• Post-install calibration: After fitting a new pack, run a full calibration cycle from the VIR50 instrument menu before heading to site. The camera maps battery state during calibration — skip this and you'll see premature low-battery warnings halfway through your first measurement session.

VIR50 shutting down at the moment the thermal sensor initialises

The VIR50's uncooled microbolometer draws a short inrush current during its startup shutter cycle — this happens every time the camera powers on or completes an automatic flat-field correction. If the battery's protection circuit has a tight overcurrent threshold, this spike can trigger a cutoff before the camera reaches the live imaging screen. A degraded or partially discharged original pack makes this worse because internal resistance rises as cells age, increasing the voltage sag under that spike. This replacement pack's protection circuit is rated to pass the initialisation transient without tripping.

VIR50 not powering on after the camera sat unused for several months

Li-ion cells self-discharge at roughly 1–3% per month under normal storage conditions, but the VIR50's standby circuit can pull the pack below 3.0V over a long storage period. Once a single-cell pack drops below 2.5V, the protection circuit latches into deep-discharge lockout and the camera will not respond to the power button. Place the battery on a standalone USB charger rated for Li-ion single cells — a direct camera charge via the VIR50's charging port won't recover a locked-out pack. Once the cell reads above 3.0V, the protection circuit resets and normal camera operation resumes.