Battery Life And Thermal Throttling
Battery life may be the most important performance metric for a mobile device. After all, it does not matter how quickly a phone or tablet can load webpages or how many frames per second the GPU can crank through once the battery runs down and the device shuts off. To learn more about how we test this critical facet of mobile computing, please read our battery testing methodology article.
Combining a relatively large battery with a power sipping processor gives the Moto G (3rd gen) a huge advantage in battery life. The ZenFone 2 and the other phones all form a close group around the six-hour mark. If you actually want to use the phone to get work done or pass the time, however, performance is important too. By multiplying the PCMark battery life by the overall performance score, we get a composite metric that gives us an estimate for how much total work can be done on a single charge.
|PCMark Composite Work Score (normalized)|
|Moto G (3rd gen)||ZenFone 2||Galaxy S6||LG G4||Xperia M4|
The Moto G’s long-lasting battery gives it the lead; you can get a lot done with the Moto G before you need to charge it again. The ZenFone 2’s excellent performance and good battery life make it a close second, beating the more expensive S6 and G4.
The score in this test accounts for both battery life and performance under CPU-intensive workloads. Both the Moto G (3rd gen) and ZenFone 2 rise to the top once again just like they did in our PCMark composite work score. This time, however, the ZenFone 2 holds a slight lead.
The GFXBench 3.0 battery test focuses on the GPU and is an indicator of battery life during intense gaming. It also effectively gauges a device’s ability to dissipate heat.
Once again, the Moto G outlasts the other phones by a significant margin, but only because its scaled-back GPU delivers less than half the performance of the other devices. The ZenFone 2 strikes a good balance between performance and longevity, both lasting longer and performing better than the Galaxy S6.
About six minutes into the GFXBench battery test, the ZenFone 2 starts throttling its GPU frequency due to the increase in temperature. GPU performance declines to 75% of the peak level by the 14 minute mark and remains there for the duration of the 60 minute test.
The skin temperature on the back of the ZenFone 2 peaks at 117 °F, which is in the same range as other high-performing devices. Looking at the thermal image, we can see a buildup of heat in the upper half of the phone. The inability to readily conduct and dissipate heat is one of the drawbacks of its all-plastic construction. The iPhone 6 Plus’ all-aluminum body functions better as a radiator, allowing its more powerful GPU to keep running at peak frequency without throttling.
The combination of a 3000mAh battery and the Atom Z3580 SoC prove to be a good combination for the ZenFone 2, striking a good balance between battery life and performance. This is most evident in PCMark’s real-world work scenarios, where it pulls ahead of several higher-priced devices. While not shown in our charts, the Galaxy Note 4 lasts longer on a charge, but the ZenFone’s higher performance gives it the edge in our composite work score and delivers a better user experience while using it — exhibiting smoother scrolling and fewer pauses overall.