This is a good powerbank for the money. Its lightweight and easy to use. I haven't used it a ton yet, only when I'm without a charger near and it works like it is suppose to. I would recommend it to anyone.
A fully charged Powerbank will charge up to 30% of an iPhone 6S Plus battery while the phone is in use, like talking or navigation app is on, or texting, etc.... That percentage increases to around 47-50% if the phone was on standby. However to get these results you have to use the Powerbank within 24-48 hours after charging it, if you let it sit idle longer than that it will start losing charge rapidly and will be left with about 1/4 of its original charge capacity available to charge the phone. One other thing and that is there is no way of knowing when the Powerbank is fully charged. Because during charging, the last light of the four LED indicator lights will keep blinking forever indicating that is still charging, unlike the other 3 lights that go solid in sequence at a completely charged quarter, 2 quarters and 3 quarters respectively..However using it on a daily basis will ruin it after 2 months and will not accept charge anymore.
Bought the Vivitar V18089 in June and it broke in August. The problem: the USB port itself is unstable. After a few uses, the USB wouldn't hold the cord. In order to physically get a charge, I had to hold the the cord. Very time consuming. And finally after only 2 months, the USB port fell inside the charger when I plugged in the cord. I would not recommend this poorly made product. Buy an Insignia from ******** instead.