how it began can be read here each generation adds more features Generation 1 is now available for D4, High/low capability but then LEDs dim to about 50% between full and empty battery LVP can be added for 0.7€ Generation 2 2 groups of LEDs or rainbow added voltage stabilisation 2.8V 18uA LDO used to keep brightness stable down to about 3V battery voltage trimmer optional Generation 3 2 groups and low battery LED (s) added low battery warning and LVP lights up with constant brightness …