I looked at the percentage of battery life that was left and I had 6 apps that wanted to be updated, which was 15%. I only update apps over Wifi and apps are set not to automatically update.

Location services and Bluetooth are always switched off. I mainly use Wifi.

I updated all apps simultaneously and after this the battery life dropped to 2%. Is this normal? Since I have had the phone about 8 months, I haven't cleared either the apps cache or system cache. Would this make a big difference to the phone performance (including the battery life)? I am running Android Lollipop 5.1.1.

Thanks in advance.

Oh god. I'm getting this phone for Christmas and I really don't want it dying like my iPhone 5 does already

I've got the S6. The other day, Google Services was causing c 15-20% battery drain, when checking the battery usage stats. I turned location services off, disabled most of the Google services (Google +, Google Books, Play Music etc), and this seems to have corrected the issue and undue battery drain. I now have 'Android OS', which is showing as top of the battery usage stats and reporting (on my way home from the office), at 132%!! What's that about..? But it's not causing excessive battery drain. Odd.

I wouldn't worry, with only 15% battery left its no surprise that updating and installing 6 apps will cause the battery to drop. The S6 has app optimisation that will manage the battery life of inactive apps. You should easily get a days use out of a charge.