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Battery Saving - a review of Juice Defender Ultimate on the S3
I have been kind of cynical about the savings possible on a phone using software. But I figured it would be interesting to try it, and the one that seems to have the best reviews is Juice Defender. I thought it would be nice if I could get materially better life without having to sacrifice the thinness of the S3. Lets see how it does.
Since I don't have any equipment to do this with, it seemed a statistical approach would work. You can both enable and disable Juice Defender from a widget. There are three versions - free, plus and ultimate. Plus and Ultimate give you some good configuration options. Ultimate gives you more than plus, but you must be rooted to use them. For instance it allows you to throttle CPU clock. If you are not rooted, buy Plus. It does everything Ultimate does on non-rooted phones. I set mine to turn mobile data off, but turn it on once every 30 minutes to retrieve email and stuff. JD does not interfere with mobile data if you start an app that uses it, like a browser. There is nothing JD does that you cannot do yourself, but it does it without you having to bother about it and can do it on schedules. I alternated enabling and disabling JD on work days, since my phone usage patterns are more or less the same over the week. I did not collect data on weekends because my usage is weird. Sometimes I won't look at the phone, other times I am on it all day. I tested for three weeks. I collected the data from 5AM to 9PM, the times the phone is not on charge at my bedside.
The results are pretty simple. With JD ENabled, my usage ran the battery down at a calculated, average rate of 3.79%/hr. With it DISabled, usage ran 4.48%/hr. This is a difference of .68% an hour. To put that in perspective, for me with JD running it takes 13.2 hours to use half the battery. With it off, I use half the battery in 11.1hours. Not a huge difference.
Notice that the widget reports what it thinks you are saving and displays it as a multiplier. In other words, if the widget thinks I am doubling battery life it would show x2.00. In fact it never showed less than x1.8 which is a severe overstatement of savings. It should have shown about x1.2.
So, is it worth it? Maybe. I can squeeze a couple more hours out of my phone without getting too paranoid about it, but it is in NO way a replacement for an extended battery, which their info would lead you to believe - and in fact what their widget is trying to tell you. Don't believe all the reviews. There is a strong element of self-delusion there, justifying the rather high cost of the paid app. Remember, JD is doing nothing you cannot do yourself with easy access to the power bar from the status bar. If you want to save the money, turn off mobile data when you aren't using it by hand.
If you are rooted, get the Ultimate and let it throttle your clock - although it seems to me the S3 does that pretty well itself, dropping the clock way back when those cycles are not needed.
One thing it DOES do when you get really low is to unconditionally turn off mobile data when you reach some discharge threshold - sacrificing mobile data for voice and text, which seems a proper way to trade remaining battery life for phone usability. But again, you can do that yourself.
All in all I'd say I wasted my money on Ultimate, or even Plus. But it was an interesting experiment and a lesson in not believing user reviews when the reviewers have not done any objective tests. It's too easy to fool yourself without hard data.