Bests & Worsts Reviews from Amazon

I'm hoping mine is defective. I have an Astro E3 Anker Astro E3 Ultra Compact 10000mAh Portable Charger (2nd Gerneration, Classic External Battery Power Bank) Slim with PowerIQ Technology (Black)which came with instructions to charge every 3 months if you don't use it. The E3 holds a charge and charges phones faster than some quick chargers. THIS PowerCore 5000 that I have wont keep a charge, used it to charge a phone on a wednesday It should have had a full charge because i had , charged it within a couple weeks. I thought perhaps I had been mistaken when it added less than 20% to the battery in the phone. I recharged it Saturday and on Tuesday, My sister used it. That is when I decided to review this. Three days after a full charge it seemed to drain the battery in her phone faster because less than an hour later this was empty and her phone had half the power it had before connecting this power core. This also doesn't look or feel as well made as my other Anker products.