I recently had the opportunity to spend some quality time with my new iPhone 4S, as I needed it for email, web browsing and Twitter. Unfortunately, it wasn’t a completely satisfactory experience. This wasn’t because it sucked down the battery like its life depended on it, although over the course of an hour when the phone was supposedly idling its charge would drop by 20 per cent and the device became quite hot.

Thankfully, my iPhone is now behaving itself thanks to some spying, resetting and fiddling, but there remain a number of suspects. So what happened?

I was on the road when I received my iPhone 4S. Understanding that I would be away from home, I planned ahead by setting up an iCloud account, complete with synced mail, contacts, calendars, reminders, bookmarks and notes, before I left for my trip. I also uploaded this data on to my MacBook Pro, and made sure that Photo Stream was active in iPhoto as well as on my iOS devices.

When I received the phone, I set it up so that it would use all the new features – Siri, location services, notifications, iCloud, reminders, and the various sync services for my several email accounts. The next day I took the phone to the beach to test the camera and try it over the local 3G network.

There have been widespread reports of problems with the iPhone 4S’s battery

After returning from a swim, I  pulled out my phone, which was surprisingly hot. It had been in the shade and the outside temperature was perhaps 25-30°C, so this was heat from an internal rather than external source. I woke the phone and noticed its battery charge had dropped 10 points. I held it and watched as its battery percentage display dropped by a point every couple of minutes.

I returned to my hotel and the phone hadn’t cooled down. I tweeted about it to see what was wrong, and received several replies from followers who said their iPhone 4S was also pulling power at an alarming rate. Several theories were offered – Siri, location, iCloud, Find My Friends – but there was no consensus on what the issue might be. A couple of people suggested that a restore would fix the problem, so I gave it a go and went to bed.

In the morning, the phone seemed better, but it was using a Wi-Fi connection rather than 3G. When I returned to the beach, the phone acted up again. Could it be something to do with 3G?

I flew home the next day, got off the plane, and in the 30 minutes I used my phone to check email and Twitter, the battery dropped by 10 points and the phone was warm. Again, a 3G connection. More Twitter carping brought more theories but no answers.

It was time to get serious. And the first step to doing that was to search through the data provided by the phone. I tapped my way to Settings > About > Diagnostic & Usage > Diagnostic & Usage Data. When you tap this last entry you’re taken to a Data page where you can see a series of entries. These are log files that detail untoward issues your device has had. Mine was full of CrashReport entries. I scanned through them and – as far as I could tell from all the gibberish in these reports – there was a problem syncing my iCloud contacts.

A number of suggestions have been put forward as to what is causing the battery drain, including Siri and iCloud

I then downloaded Recession Apps’ System Activity Monitor (69p). This is a utility similar to the Mac’s Activity Monitor that details the processes your iOS device is using, as well as indicating, in real-time, how hard the processor is being pushed. When I launched System Activity Monitor and tapped the Processes button at the bottom of the screen, I found the processor graph jumping into the 60 per cent range every few seconds. This activity was reflected in two entries competing for the top spot – dataaccessd and CrashReport. The iPhone appeared to be in a crashing loop, where dataaccessd attempted to do something, blew up, tried again, blew up, and so on. This was killing the battery.

Based on the information I now had, I switched off contact syncing in iCloud. I returned to System Activity Monitor and everything settled down. The iPhone wasn’t completely inactive, nor should it have been. But the user processor percentage was now running under 3 per cent most of the time.

In the hope that I could confirm the issue (and after a colleague suggested that a corrupt contact could be part of the problem), I travelled to Settings > General > Reset > Erase All Contents and Settings. This wiped the phone.

On restart I chose to set it up as a new phone rather than pulling a backup from my Mac or iCloud. I also made sure that it didn’t sync any data with iCloud until I was ready. When the time came, I switched on contact syncing within the iCloud screen and fired up System Activity Monitor. There was a lot of activity for the first few minutes as the iPhone grabbed my contacts from the cloud, but then it settled down. There was no crashing loop apparent. I then proceeded to switch on calendar syncing and checked System Activity Monitor. Again, no problem. And so it went, switching on one iCloud syncing option, checking System Activity Monitor, and moving to the next one. At the end, everything was fine.

Another account perhaps? I configured a Gmail account using Exchange rather than the usual Gmail option. No problem. A regular Gmail account. Nope. Yet another Gmail account used by my ISP? No. Maybe this long-dormant Yahoo account. No. A standard POP account? No.

The System Activity Monitor app will detail your iPhone’s processes, so you can see what’s draining its battery

In the end this story may have to remain a mystery. But what I know is this: the combination of crash reports provided by the iPhone and System Activity Monitor helped me determine that I had an issue with contact syncing that caused my iPhone to drain with alarming rapidity. But wiping the phone and syncing via iCloud solved the problem. Yet it did so the second time rather than the first. Why? I haven’t a clue.

If your iPhone is draining – not just a bit more quickly than other iPhones you’ve owned, but in a “what the hell” kind of way – consider aiding the cause by troubleshooting it in the way we’ve described (or any other way where you can make real observations). And drop us a line – email the editor on [email protected] – to let us know how you get on.