PNV-57A/E battery pack

A battery pack for Russian and Polish PNV-series night vision goggles.

Assembly requires no modifications to the goggles and no hardware*. The battery pack halves clamp around the connector in the NVG's power cable. This project contains both a 9V version and a 18V version, both of which work and assemble in the same way.

The spring-loaded bayonet lock from the goggles' power cable connector is used as a switch: the battery housing clamps around the locking sleeve, leaving the connector free to rotate inside it. The geometry inside the housing locks the connector in off-position when turned 90 degrees and prevents overtravel. In on-position the connector makes contact with the battery terminals, thus powering the device. The 18V version might require you to bend the connector's contacts outwards slightly to ensure proper connection.

To assemble, the locking collar is first slipped on the wire, one half of the housing is placed on the connector with the battery, checking that the polarity is correct. The other half of the housing is placed on top, and the locking ring is threaded in place, securing the assembly around the connector. Both versions use the same locking ring. 

Tolerances with this model are very tight; screwing the locking ring down requires a lot of force. It is highly recommended that you dry assemble the parts together a few times before assembling them on the goggles. The battery and the connector from the goggles' power cable should fit snug, but should require no force during assembly. 

Both the 9V and the 18V version have been tested with a Russian PNV-57A, PNV-57E and a Polish PNW-57a, all of which have slightly different (but cross-compatible) connectors.

*The 18V version requires a loop of wire etc. conductive to connect the batteries in series, so almost no-hardware. The 9V version requires no hardware at all aside from the battery to work.