klein tools makes these head lamps good for an more than an 8 hour shift on the 100 lumen flood they claim 14 hours I think either way they are good
if you buy their hard hat it has a mount front and rear and yes I probably look stupid working on stuff with my hard hat on but it is the most comfortable way to wear a head lamp
they start blinking the main light of and on when you have low battery , you can switch to low and get about 20 more minutes or get to where you can switch lights
charge them off the truck they don't seem to drain the truck battery keep one on the charger and one on the head they charge in less time than they run for
https://www.amazon.com/Klein-Tools-...amp;hvtargid=pla-1162858765430&psc=1if you have any power tools with the batteries like RIgid or Milwakee they have lights that run off the tool batteries for some time also
Rigid and Milwauke also have fans that run for about 4 hours at a time on the tool batteries
I charge the tool batteries off the inverter in the truck while driving , but a very small generator would charge them also