Best iPhone 4s battery case?

[ciberkarlos]

Hi everyone, i'm looking for a battery case for my iPhone 4s. I've searched at Amazon.com, and every single case i found has some bad comments which makes me doubt. Apparently, all cases i saw may not fully charge the phone and/or are to heavy/poor quality. Could you recommend a good iPhone 4s battery case which could really add an extra battery charge with acceptable dimensions and weight?

Thank you very much.

 

[Ann P]

How about the Mophie Juice Pack AIR? I used it on 4S and have no complaints. The build quality was up to par and gave me that extra charge that I needed.

 

[ciberkarlos]

How about the Mophie Juice Pack AIR? I used it on 4S and have no complaints. The build quality was up to par and gave me that extra charge that I needed.

What about its weight/dimensions? Does it fully charge the iPhone 4s or just add few more hours?

Thanks!