FMA PVS-31 Battery Housing with IR Lights — Multicam

The FMA battery housing for the PVS-31 is the rear module that powers compatible night vision devices and integrates two IR lights with strobe function for position identification in low-light conditions. It replicates the original PVS-31 dimensions: 85x40x88 mm, weighing 90 g without batteries. Helmet attachment is via internally applied quality velcro, with no tools required.

The housing accepts four standard AA batteries, arranged in two groups of two (group A: positions 1 and 4; group B: positions 2 and 3). The two groups are connected in series, so the housing delivers the combined maximum voltage of one cell from group A and one from group B, with a controlled output voltage between 2.0 V and 3.5 V. Operation with just two batteries is also possible; the manufacturer advises against rechargeable batteries without stating the reason. Gold-plated contacts reduce contact resistance and susceptibility to oxidation, a relevant factor in humid conditions or during prolonged temperature swings.

The two IR lights at the top emit at a wavelength between 820 and 850 nm, invisible to the naked eye but detectable by image intensification devices. The strobe function improves distinguishability over continuous IR sources, useful for team position identification. The asymmetric selector is designed for blind operation with gloves, without needing to visually locate the control. The trade-off of this system is that the chosen IR wavelength ensures broad compatibility with most image intensification devices, but may be less effective with systems optimised for wavelengths above 900 nm.

Key points

• The asymmetric selector allows gloved operation without direct sight of the control.
• The two-group series configuration supports operation with 2 or 4 standard AA batteries, keeping output voltage stable between 2.0 and 3.5 V.
• Gold-plated contacts limit oxidation and maintain electrical continuity in wet or dusty environments.
• Dust-proof gaskets protect the battery compartments from external elements without adding significant weight.
• The 820–850 nm IR lights with strobe function are detectable by the main image intensification devices in current use, suitable for night-time position identification.
• The dimensions and velcro mounting system maintain compatibility with the standard PVS-31 housing without any helmet modifications.

In the box

• FMA PVS-31 battery housing with IR lights — Multicam