Very good battery backup,
Verified Purchase(What is this?)
This review is from: Anker® 2400mAh MFI Apple Certified Premium Rechargeable Extended Battery Case for iPhone 5s, 5 [18-Month Warranty] (Wireless Phone Accessory)
Anker promise 120% from a single charge. I seem to be getting close to 110% on my iPhone 5, which is quite impressive especially given the price and MFI certification.
The only complaint I have is that its is a bit fiddly to get the phone out of the case, but I don't think its a major problem. I am not a regular user, I use the battery only when I am travelling - taking photos, using maps, browsing on the go. It's perfect for me.