Wear NVG (can be used with headstrap or tac helm) with a dead battery inside
turn on NVGs or leave them on (if battery has died while using NVG effect)
take NVG assembly (strap and/or helm) to hand and take out dead batt
Replace battery slot with working battery and NVG effect comes on.
NVG assembly can be dropped and passed to next player for exploit.
Effect ends when player dons NVG and manipulates battery again