45 minutes - 2 hours
battery was running down. I was disappointed that the battery that once lasted nearly a day was only giving me 3 hours.
It took 3 hours. It was kind of hard getting the case open and the battery was held in with strong tape. The battery wires were covered in hard to remove silicone and I didn't have any desoldering equipment. Also, I stripped one screw and lost another. I decided to put the remaining screws into areas that were easily accessible and forget about the others.
Make sure you have good desoldering equipment and a proper screwdriver. The one included was not quite the right fit; that's why I stripped a screw. It would have been nice if some desoldering braid was included with the kit