practical test of how much the battery degrades from fast charging. a batch of six identical batteries for Samsung Galaxy S20 Plus (EB-BG985ABY) with a stated capacity of 4370 mAh and an initial actual capacity of about 3900 mAh is tested. the batteries were 100 times subjected to a resource test of full charge and discharge. This is approximately 100 days of phone usage. fast charging at 5 amps led to a noticeable decrease in capacity. Over three months of fast charging, the batteries lost an average of 1.6% of their initial capacity.