Recharges my smart phone over two times a day.

I tried  2000 mAh, but it was never enough. At 8000 mAh this battery recharges my phone over two times in a day. So now my Nexus phone can run out by noon, recharge over lunch and run till four, recharge and run till 9 PM. All without finding an outlet. Cool.

It also charges my phone faster than the AC adapter.

I have used it daily for several months and it hasn't lost it's power yet.

Finally happy
Steve

Amazon.com: Aluratek APB02F Dual USB 8,000 mAh External Battery Pack and Charger for iPod, iPhone, iPad, eReaders: Electronics

Other models: 

APB02F