Everybody is forgetting the most important fact. Just because a battery or power bank is labeled 10,000 mAH, doesn't mean it is 10,000 mAH. Is there a good way to test a battery/power bank to verity what it's real capacity really is? Calculating a battery's or power bank's capacity by using the printed on the label data is pure fantasy. Most Chinese devices data are wishful dreaming. Is there a circuit or other method that can drain a fully charge power storage device to it's half voltage point and then calculate it's storage capacity (my thought of how to do it)?