A brand new battery will last about 3.5 to 4 hours. After a couple years use that same battery will drop by about one hour. With the in- car charging device that is included with the purchase we start recharging part way to our destination so the battery is at 100% charge when we arrive. I recommend you do two things if you decide to buy this system, first opt for the lifetime warranty and buy at least one spare battery. We always carry a spare wherever we go. Good luck with whatever you decide to do.