I too keep an eye on tham. The only thing that are making a bit nervous is the fact that my Nitecore D2 have a little, just a little of burnt smell, it's a electrical burnt smell. There's no noise and the baterrys are in normal temperature. The charger is not too hot. I only can smell when I am too close to the charger, like 5cm btw the charger and my nose, haha!