Hi. Welcome to our COPD community. That's a great question about portable batteries. Typically, how long a battery lasts depends on the brand and the liter flow you're using. For instance, an Inogen portable oxygen concentrator can last around 4 hours at 1 liter per minute (LPM), 2 hours at 2 LPM, and approximately 1.5 hours at 3 LPM. I'll cover more details in an upcoming post, but I hope this helps for now! Wishing you all the best. John. community moderator.