I bought (ICool 50,000 mAh quad-port power bank) on mid December last year. To my surprise, I could only use this charger for 2 weeks! This charger functioned such that when I charge it, 0 means empty and 99 means full.
When I used it on first week, I could charge my Samsung notebook and iPhone quite a few times. On the second week, when the charging capacity reached 58, it turned to zero immediately. Meaning to say, the capacity became 25,000 mAh instead. On my third week, even though I charged the charger to full to 99, I could only charged my iPhone for 10 mins and the charger auto off!
I will never buy technology products from Groupon anymore!