I upgraded a 6 Plus to a 7 Plus and have had similar slow charging issues. The 6 Plus was adequate but the 7 Plus is disturbingly slow and I have to essentially leave it plugged in always and do not notice any longer life in the battery. I have the same apps, use them the same way and the battery and charge time is very disappointing, less than half the speed of the 6 Plus. The phone is only a month old whereas my 6 plus was over two years old. I purchased two iPhone 7's for my daughters and they frequently run out of battery during the day which renders the phones somewhat useless. I will not be purchasing any more iPhones until they rectify the problem.