Hey community,
I’ve come to the conclusion that monitoring your apps / processes seems to be a potential fix for quickly drained batteries.
However:
I don’t think that deleting / deactivating apps like facebook, dropbox, etc. can be the solution. Those are standard apps! If you have 100 processes running - fine. But I’d like to think that “normal” usage of the phone will still be possible for at least 1 day with one full charge.
Reading that some FP2 batteries power a FP2 up to 5 days (granted, probably not with much user interaction) still leaves me wondering whether there is a problem with my phone or not. Something like a “standard benchmark” would be interesting, just to see whether the battery life of my phone is more or less as expected. 
Any suggestions?
Maybe a measurement of the energy consumption with BetterBatteryStats while using the phone for one hour (i.e. surfing with Firefox?) could be an idea…
Best comparison would be if Fairphone finally deliver a official battery consumption data report as it was available also for FP1. Now FP2 is already more than 5 months old - I would expect it should be enough time to perform a meaningful test.
Of course the next step would be to improve battery life, at which the community was not very successful until now (including me, beeing quite dissapointed if I compare 5days FP1 to 1-2days FP2 with approx. same usage behaviour :-/ )
I also have the feeling that my FP1 battery lasted appr. 1.5 times longer, while I don’t think my usage patterns have changed.
Though I was already sceptical when looking at the specs. of FP2, as the 2400mAh battery doesn’t convince me with a 5inch screen and stronger hardware. Personally I think that battery time became a victim of the modular design, as probably there wasn’t more space for s bigger battery.
My consequence was getting a power bank, which isn’t exactly what I desired (in terms of ecological thinking), but otherwise I just don’t make it through my regular work related travels. The FP1 was just sufficient, the FP2 needs extra juice.
There was actually a really negative article about the Fairphone 2 on XDA when it was announced. The article criticized that the battery is rather small, and I had to agree, at least to a certain degree. (I do not feel like looking for the article right now; I mostly did not agree with it anyway.)
Unfortunately, I do not remember where I read it, but I think one of the Fairphone members indeed said that it was a problem to place a decently sized battery in the modular phone. (As I do not have a link and I am quoting from memory, I might be wrong though.)
Anyway, I did a quick research, and I found this article about the battery life of the Nexus 5 (with a 2300 mAh battery). Indeed, the Nexus 5 lasts at most 4h 45 min, and it seems that Android Lollipop did not really improve this. (However, I have also found other articles where a considerable improvement is reported after the upgrade from KitKat to Lollipop.) Anyway, we should not expect a miracle when it comes to the battery life of the Fairphone 2 with its 2430 mAh battery.
However, I would not be surprised if future FPOS updates will improve the situation. Maybe the “flickering screen” issue is one example where the energy management has not been optimized yet (but that’s just a guess).
Well, yes - no. Argh, there not a definitive answer.
On the one hand, if every of these 100 processes decides to constantly keep the CPU busy just a bit, you get a considerable CPU usage (and therefore energy drain) even if the screen is not active. Apps should not do this, but if they do…
On the other hand, Google has been aware of this problem, and Android 6 (Marshmallow) has introduced the “doze mode” where background apps are indeed stopped when the screen is off. (There are exceptions e.g. for push services, but it is not trivial for an app to be exempt from doze.)
Nice eh?
Stupid phone… 
I know that I shouldn’t, I don’t want to but I start thinking about buying a new functionning phone… Maybe sony dual or something like it… I hate the idea but I can’t continue with that phone that doesn’t do anything right…!!!
This difference could possibly be your solution.
It seems your FP2 never goes to sleep.
I am heavily using my completely charged device this morning since 06.15 am.
But I haven’t too much bloat installed.
Just wanted to share…
So what do I need to do?
Your battery stats are a dream for me…
In a first attempt I would try to isolate the misbehaving app without a hard reset.
Switch on your Samsung and compare the lists of additionally installed software.
If there is a difference on your FP2, clear it off.
Then delete all apps you don’t essentially need - e. g. weather widgets, K9 pure widget. Especially Fitbit may be a battery hog. Also consider cancelling Twilight, LightManager, McAffee etc. temporarily.
Sometimes Dolphin seems to make problems too. I would recommend the Lightning browser.
Check all apps (K9?, WhatsApp, Facebook, dropbox … ) that need regular server connection and where possible extend the peroid of synchonization or disable it. Even Swiftkey needs sync for predictive texting.
Do you need Bluettooth activated all the time?
Disable the Wifi search option if applicable.
After that please watch your FP2 for a day and report back, good luck!
@evidemment: do you use an SD card? If yes, have you ever tried to take it out as some people had problems with power drain related to some SD card.?
Good point.
I had recommended that already but the answer was not completely clear.
Just for the record, @georgmayer solved his sd-card induced battery problem this way.
This could be worth a try for you @evidemment since your phone is already rooted.
// “Sd-card induced” is not quite correct. The underlying cause is more likely a basic Android problem or an app inbuilt bug.
Ok I took the SD card out and 1 min later CPU was really really hot and battery % dropped 4%!!! So I kind of thinking that’s not it…
I’m trying something else now… I took my SIM 2 out now without putting the SD card back in… CPU is really hot again…
And by the way… installing and deleting applications will take forever and it’s not fun… As said before, I should have basic usage of my phone without having to delete apks I use… As for Fitbit it’s new and definitely not the problem as battery drain was there before I installed it…
Install a process monitor like AnotherMonitor from the Google Play Store or F-Droid.
Then you can look which process has a high CPU usage.
Ok there’s a great chance that the battery problems are due to the second SIM card. What is weird is that it’s new and that at the begining it didn’t create any problems.
I need that second SIM and it’s a prepaid one… what should I do? I can’t just put it in the phone everytime I want to use it…
I’m really glad you’ve found the solution 
Can’t you just let it sit in place and disable it until you need it?
People as supposed to be able to get me on that phone number… not often but…
And a dual SIM phone is supposed to work with 2 SIM cards doesn’t it?
I would suggest to ask your provider for a replacement SIM.
