Acer V3 572PG - Clean Install caused bad battery

So I bought an Acer V3-572PG, core i5, nVidia Geforce 840m, with a boasted 7 hour battery life.

It was great, however it came pre-installed with a lot of bloatware, which slowed it down (and there was even an unknown service running in the background that stated in its privacy policy that I had not agreed to, that it was allowed to track my movements on the internet and send it to them. Which I was NOT okay with).

So I bought windows 8.1. Wiped the hard drive and installed Windows 8.1 again.

However now, my 7 hour (sometimes 11 hours, if I reduced power settings enough) battery life, has been reduced to 4 hours.

So I assume that Acer has modified the underlying OS to cut down on certain processes to extend the batty life considerably.

Any idea on how I can bring my battery life back up? The long battery life was the main reason I bought this laptop. And I'd be rather if I lost that feature.

Thanks!