I keep an eye on iPhone and iPad battery life following all iOS updates and I have to say that the iOS 7.1 update wasn't kind to the power pack. I saw the battery life of my iPhone – and several other test devices – go from "great" to "poor" overnight.

Do I have numbers to back up my assertion? You bet I do!

Image: CNET/CBS Interactive

I've collected a fair bit of data for my workhorse iPhone 5. Pre iOS 7.0, six hours of use would take my fully charged iPhone down to 74 percent.

Note: I always measure from 100 percent because I can't guarantee that the discharge curve is linear, and this figure is an average over many six-hour runs to give me an "average" use figure.

Following the upgrade to iOS 7.0 I saw battery life drop a little, but it came back to normal quickly and so I put that down to battery calibration. Some iOS updates seem to wipe the battery calibration data and it takes a few recharge/discharge cycles for things to get back to normal.

However, following iOS 7.1, I started seeing the battery drop to around 48 percent per six hours of use, which was a significant and very noticeable level of degradation.

Put that another way, on a long day – many of my days are long – I would need to recharge my iPhone to make it through the day. You could actually watch the battery counter drop, and on more than one occasion I saw it drop several percentage points in one go.

Even with my toolbox of iOS battery life tweaks I could only get a few extra percentage points out of the battery. After isolating the Facebook app as one of the biggest guzzlers of charge , I got it so I was dropping to about 61 percent per six hours of average use.

Better, but far from stellar.

Then came iOS 7.1.1 . Following this update I've noticed that things have improved dramatically, and now battery life is only falling to around 76 percent per six hours of average use, which is better than what I was getting pre iOS 7.0.

Can't grumble with that.

Note that this is data collected by my handset (other handsets show a similar pattern) and is based on my apps and my usage of them. Your mileage will undoubtedly vary.