[YotaPhone] euroclie:
Battery drain Tests

I've done some testing yesterday that I'd like to share with you all here, maybe it'll help people decide if the YotaPhone 2 is the ideal device for you or not before purchasing one... As for me I'm a very happy YotaPhone 2 user, but given it's quite an expensive toy, I'd hate people to be disappointed with battery life just because they have unrealistic expectations on this topic.

So what kind of tests did I run? Not too scientific ones, I'm afraid, but then I'm just an end user with some spare time, so it's aimed at giving people a rough estimate of what to expect than anything else.

TLDR:

The EPD is useless if you intend to use graphic or processor intensive apps, but is a clear winner for apps that update the screen less frequently. No big surprise, but still worth confirming! ;)

It also means that unless YotaPhone releases the YotaPhone 2 SDK and developers start making apps that use the EPD in an optimised way, we'll have to use YotaMirror which may not always be the most power-efficient solution, and use exiting apps with an appropriate interface and settings.

Test 1: Display/Processor-intensive applications: I chose to run a processor-intensive game (Summoner's War: Sky Arena), with 3D graphics and a display that's constantly changing, since even outside of the arena/dungeons game phases, there are plenty of animation in the interface. Playing the game usually makes my device quite hot, so I consider it to be quite power-hungry.

In the first hour of testing, I used the main LED display, with brightness setting set on auto. Yeah, I know, it means that depending on the ambient lighting, I wouldn't necessarily get the same results if I performed the test a second time. In the second hour of testing, I switched on the YotaMirror function, and used the EPD on the back of the YotaPhone 2.

I used "Battery Widget Reborn" to track battery usage, it produces a nice graph (enriched and attached to this post) as well as .CSV export I used for more acurate calculations.

If you look at the graph, there's not much of a difference between the first and second parts of the test. Looking at the CSV data, I found out that playing this game gulps 29% of the battery every hour if you use the LED display, and 32% per hour with the EPD! :(

What does this mean? Does the EPD suck when it comes to helping you get through the day with some battery juice to spare? No, I wouldn't say that. What it means, as far as I can tell, is that the power drain of the LED or EPD is, in that situation, not the main factor, and if your CPU/GPU is running full speed, then your battery life will plummet regardless of which screen you're using. I suspect that even if you could somehow manage to play with both screens switched off, the battery drain would still be considerable.

More troubling is the fact that it seems that the battery drain could be slightly higher when using the EPD. That would need to be confirmed by additional testing, but an explanation could be that YotaMirror is most certainly an additional process running on top of the other application you're running, eating some processor resources each time the display needs to be updated, and if the display is constantly changing then the additional drain may not go unnoticed.

Test 2: Slow screen refresh applications: For this second test, I used YotaReader and enjoyed reading an ebook for approximately two hours. The first hour was spent using the LED display, with auto brightness, and a white background/black text setting. Then I switched to the EPD for some more reading. I had some issues with a stuck YotaReader, probably due to a buggy epub file, and performed a reboot before using the EPD, which is the reason why there's about 15mn and a bump in the curve between the two parts of the test.

The graph is harder to read, since the curve is much flatter, but you can still see that the EPD is more power efficient than the LED! <relieved sigh>

Using the CSV data, I calculated that reading with the LED display eats only 13% per hour of your battery life, while you get a nice 5% per hour using the EPD.

Again, what does it means? That if you use an optimised application (YotaReader) that displays a screen which is not too frequently updated (once every 30 seconds, more or less), you can get more than two times the normal battery life. I suppose that displaying a clock on the EPD, or notifications (text messages, mails...) that are updated at the same frequency would give similar results.

Conclusion

The bottom line seems to be: if you're using your YotaPhone "normally", with games, video, or whatever it is that you're doing on any other smartphone, then the EPD will only provide a minor improvement of the battery life, if at all. Don't forget that the battery isn't removable, so you can't swap at mid-day to put a freshly recharged one. On the other hand, the YotaPhone 2 itself is a neatly optimised beast, without too much added software layers on top of the vanilla Android, so you can still get decent results. I initially had more battery life remaining in the evening with the YotaPhone 2 than I had with my previous phone, without altering my usage patterns.

If you want to fully benefit from the YotaPhone 2 EPD, you may have to adapt to it and change the way you handle things on your smartphone. Using YotaPhone-optimised applications is clearly a must.

I grumble to see that YotaPhone seems to be spending so much time in selling their phone in more countries everyday when the developer's page still says "Coming soon".

Don't get me wrong, I hope that more and more people get the opportunity to buy and use one, and I'm convinced that once it's released in the US, for instance, there'll be even more people interested in the device, which means also more developers wanting to use the EPD, but until the SDK is out, we can only hope to use the native, optimised YotaPhone applications or the incredibly-usefull-but-yet-not-so-power-optimised YotaMirror function.

Part of adapting to the YotaPhone 2, aside from using YotaPhone-compatible apps, is also to favor applications which interface do not involve too many flashy animations or screen refreshes. The less animations/videos, the better it will look on the EPD, and the less battery drain. Also smaller pictures or no pictures means more text displayed on the EPD, which in turn leads to less screen refreshes to display the next page. Things like page scroll instead of line scroll would help, of course. There are probably plenty of currently existing apps that can be fine-tuned to achieve that, and which can in turn be used with YotaMirrot to provide both a satisfying user experience and a minimal battery drain!

I'd be happy to read your comments, and if needed update this (already too long) post to reflect other people tests or feelings on this subject, so feel free to correct me or add your two-cent! :)