I have had two nights out with it so far, the led turned red when i was comming home last night, meaning it was running low. I was out for a couple of hours both nights but had it on dim alot of the time to spot and then full beam for short bursts when the dog was running. Total time i havdn't a clue but acebeam quote 3.2 hours on full beam with 3400mAh panasonic cells. Indipendsnt reviews on youtube say the figures are pretty accurate. Good thing about them is they have no memory, meaning you can charge it after any period of use without harming the batt. So whack it on after every night out