Yes, it is possible to replace the battery of the HTC Vive Focus 3, which means that you will be able to replace the battery when it runs low. The battery of the HTC Vive Focus 3 is located in the head strap of the device. The padding on the inner part of the head strap can be removed. Magnets hold the padding in place, so you can simply pull on it to remove it. There is a locking mechanism on the battery that unlocks when pressed, allowing you to remove the battery.