Choose external battery pack?

Hi, i would like to buy an external battery pack for my two phones galaxy s3 and iphone 5, so what's the best battery pack for them if i would like to charge both twice times(less or more), and what the correct amp port for each one?

I have a galaxy s3 and an iphone 4s. I actually got a 6000mAh battery charger first but I found out that it can only charge my phone about twice. So I get another one which is RavPower 10400mAh. Can't tell how much I love it. It comes in portable and does look like a neat one. It has 2 outputs so I can charge 2 of my devices at the same time. I would strongly recommend this one to you. You can get it from amazon store.

  • Which External Battery should i go for. I'm confused, trapped decision: X? My intention was 30000maH battery back ofc… But after i saw this 10400mah features i'm baffled… And ye kinda pricey but tough choice… Look at the safety in this https://deals.iphone… L-battery-brown and this was my first intention… https://deals.iphone… Ah-battery-pack but after that 10400mah pack details… I'm baffledd…
  • What is a reliable battery pack for an iPhone 5? I need to purchase a battery pack for my iPhone 5, something that would extend my battery life for a few hours longer/ charge my iPhone while on the go. I need it to be something reasonable in price too. Is there a specific battery pack that you would recommend? Product review would be awesome!
  • Sound coming from my external iPhone battery? This may seem like an awkward question, but since when did batteries make a whirring sound? It's not like they have movable parts inside like a hard drive. I'll post the link to the exact external battery later.
  • LG Motion 4G: External battery cases? I know the iPhones and Samsung Galaxy S3s have external battery cases, like the Mophie Juice Pack (iPhone) that doubles the use time of their phone. Is there any known CASES that can do this for LG Motion?