Using two 18650 from old laptop battery, the headlamp is able to run on reasonable walking power (~150mA, body is completely cool) for 25 hours, then it went to emergency mode with 40mA consumption and worked for another 4 hours.

The charger was able to charge 3896mAh into batteries after this test.

Also, I measured the weight of the headlamp. The lamp itself weights only 80g! Battery box is 45g and the battery pack is 96g -> the whole project weights 221g.

Last thing missing is head strap and the project is finished! (Or I could just simply drill some holes to my helmet and use the screws to hold the lamp on its place. But I use the helmet for both caving and climbing, unmounting and mounting the lamp everytime I do a different sport would be pretty annoying...)