The battery life test is one of the world's most difficult things to rate, thanks to the sheer range of things you can do with the phone to keep it from throwing out all its juice in a heartbeat.
For one person the Galaxy S4 is a treasured beast, only brought out into the light to check emails manually once an hour for most of the day. For the next it's an all-powerful media player, one that will be streaming movies over a 4G connection while auto-updating every app under the sun.
The good news is that the Samsung Galaxy S4 is able to handle all the things you can throw at it and still keep the 2600mAh battery chugging along at the end of the day. I found that in general use it was very well received.
TechRadar's usual test is performed on the commute to work, the time when we're all glued to our screens. For this test, like all other phones, I streamed audio over Bluetooth headphones (Rockaway Novero, if you're asking).
A 10 minute cycle ride with music playing dropped things by 1%. Streaming video over 4G for 10 minutes with full brightness on the screen pulled down another 3%. Then it was more music for 30 minutes, which ate another 2%, and then downloading a 86MB game file over 4G, which munched 3%.
A little more music playing, combined with general email checking and testing out the air gestures, air view and smart scroll saw a battery drain of just over 10% for the hour I was trundling to work. That's really impressive, as I reckon high drain capability of 10% per hour will lead to more than enough juice come the end of the day.
I never found myself in that situation, which is great. You can always pop in another battery, thanks to this being removable, but in truth, it wasn't needed.
I will say that those that like gaming, movie watching and internet browsing will struggle to make the battery last on this phone, as the screen is the biggest drain. That sounds obvious, but I'm actually happy that the Galaxy S4 isn't one of those devices that will see your battery juicing down from an overly-enthusiastic background syncing process.
After a few months of using the Samsung Galaxy S4, I found that the battery life was definitely better than other models on the market. With medium to low usage, you'll easily get to 50% by the end of the working day, and that's including some music streaming, internet browsing and video watching.
The Galaxy S4 has an excellent sleep mode that means that when it's inactive it can really drop the drain on the CPU, and achieve that in a much better manner than other devices.
While the S4 is OK, the lower-end CPU isn't up to the power of the Qualcomm 800 seen in the LG G2 and Nexus 5, these are much more power efficient and are even more adept at connecting to wearables without an impact on battery life.