Nitecore HA27 _ teardown and turbo chart

An interesting outdoor headlamp with a heatsink and high-quality light. However, the turbo doesn't actually work: when the battery is slightly discharged (<4.0V), turbo brightness drops to almost nothing. Also, one of my NLB1500 batteries was defective.

HA27 is a very good headlamp, but I'd like to see a lighter version and without these annoying issues.