'LedLampe IV' was developed from cavers for cavers and is commercially offered by Spelemat / TechTonique SA (Switzerland). This headlamp is nearly unknown outside of the French language area unfortunately, because this lamp is very good at a remarkably low price.
LedLampe IV was used with LiIon battery from Petzl Ultra during the comparison. When using the yellow battery case from Petzl Duo the headlamp will output less light in boost mode, because usual NiMH AA cells are too week to deliver up to 5A and corrosion of the contacts in the yellow box may produce additional voltage drop.