The case houses a 3500mAh battery which will allow you to get almost two times the battery life as you would from the phone alone. Charging the case and phone simultaneously from almost dead will take about 10 hours depending on the charger you use. In this case, no pun intended, you are much better off using an after market charger rated for at least 2A. Other than the small headphone jack and flimsy kick stand this case does its job very well. It is easy to install and once installed holds the phone very well and keeps it safe. Another advantage of the lightning port on the case is its ability to pass data so you can sync with iTunes without removing the case.
Overall this is a nice case that gets most things right. I can get over the flimsy kickstand but do wish they had included a short headphone extension like some other cases include.
If you are interested in purchasing the Btopllc iPhone 6s Battery Case it can be found here.