FP2 battery saving challenge


25 hours of having used the phone for just a single phonecall and nothing else, Wifi and mobile data turned off

25% drop (from 67 to 42)

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Doesn’t seem like Wifi was turned off


So that’s why I saw a big drop! I wonder if I did use it last night and forgot to shut it off or does the phone or some app turn it on on it’s own? Have to look more closely at that.

My submission for the challenge: from 100% to 20% in 3 days and 8 hours.

With the advice in mind to keep the battery between 20 and 80%, I’m gonna charge it now.

Usage of today: all data connections are still off, I used my FP2 as an mp3-player for half an hour and made a phone call (3 actually, but 2 weren’t answered).


Hey LaurieJ, and why is that? I loved JuiceDefender on the FP1. Why doesn’t it work? And is there no alternative that does the same job?

Hi Hennu, I think it’s something about more recent Android versions not supporting the same operating system hooks, rather than a fairphone specific thing, but I’m not sure. There’s quite a few threads on various forums about juicedefender + lollipop suggesting it is a common issue, but i’ve not delved into it in detail. Try searching for “juice defender lollipop” for more.


since I switched back to my FP1U and do not use my FP2 in a regular basis, I could extend my battery duration:


  • no SIM cards
  • screen brightness: auto
  • Wifi only active when needed
  • Wifi only 2.4GHz
  • activities: Internet browsing
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Ehrm …
unplugged 15 hrs ago. I … kind of … doubt what I see but well, the next days will show ^^

One SIM, 2G, no Wlan, no Bluetooth, no mobile Data (I use them only on demand). SIM-Card however works, just tested and called myself with another phone. Deactivated serveral apps (youtube, chrome, google maps … ).
I fear there will be a rapid drop somewhen and my battery is not calibrated correctly, but I am curious enough to test it - i wont use my fairphone the next days and will only check the battery stats now and then …

3 days passed. 82% left, estimated remaining time: 12 days.
What sorcery is this? xD


2 posts were merged into an existing topic: FP2 Battery Problems (drains quickly, CPU gets hot)

Here you see the result of my best values achieved in my “real life usage”.
It is with a very low overall usage and a high percentage of stand-by time - and I am still far from happy with this:

Some numbers of the Android Battery screen:

  • WLAN: 2d3h = 32%
  • Stand-by: 3d19h = 23%
  • Display: 2h19 = 17%
  • Calls: 1h20 = 6%
  • Provider/SIM-Stand-by: 3d21 = 5%
  • Android System (active CPU): 1h30 = 2%
  • Android OS (CPU): 1h7 = 1%

I am using “conservative” as CPU governor for ALL (!) cores, and have CPU frequency always limited to 1GHz (instead of 2.5GHz) and never used the display with full brightness.

The havey drops in the curve are either some surfing (10min?!) or doing a call (5-15min?).
All-in-all a usage of about 2h19 with activated display and 1h20 doing calls not achieving 4d duration althoug I really used the total battery capacity (98%) is not very satisfied.
With my FP1 I could EASILY do the same and only go from ~ 90–>20=70% battery!

So there is massive room for improvment, althoug I not really know, HOW?!

If I calculate overall consumption: 98% / 3d20h = 1%/h
During the night I normally have 0.4-0.5%/h with 2 activated SIMs (FP1 had 0.1%/h).

I will continue to work on it - any suggestions how to improve?


A post was merged into an existing topic: FP2: Research on power consumption in IDLE and STAND-BY to prolong battery duration

I … give up. 7 Days passed, 56% left xD
I want to use my FP2 now and the battery shows astounding stamina

Total estimated battery time:

16 days.

Statistics show no relevant jumps, thus I think the estimation is reliable.
This is … impressive I think, although only used as passive mobilephone (“being in my pocket waiting for call”). Of course the time will be way shorter when using wlan, mobile data etc, its ok for me to charge it every or every second day in this case. But I need a phone that is usable after a weekend forgetting it in my backpack while still being able to recieve a call in this time. It seems I got a phone that I still can use after forgetting it for whole 2 weeks. Nice one.


Thanks, thats a good number. So we can calculate a value for
##pure Single-SIM-Standby of 0.26%/h
I find this value not outstanding in general, but also not bad.
It is slightly lower than I observed for Dual-SIM-Standby…(will post values later).

I also would be really interested in the used CPU states during this 7 days, but I guess you dont have any suited app installed (like BetterBatteryStat, KernelTuner,…)?

So let us see later, how it behaves in your “normal usage life” :wink:

I manage to get this by using the aeroplane mode combined with a nifty little app called PowerPRO (available on Google Play and 1Mobile market). Starting from a full charge at 6am I use my phone for about 30 minutes to read, or watch a video or listen to a podcast. Then it is on aeroplane mode + ultra mode (PowerPRO) most of the day between 8am and 4pm - apart from a few message checks throughout the day. after work I cycle back home for over an hour, using mobile data, GPS and the Strava exercise tracking app. When I arrive home around 5.30pm the battery is still at about 60%…

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How u be able to set the CPU ?

I use https://f-droid.org/repository/browse/?fdfilter=Kernel&fdid=com.grarak.kerneladiutor this app for this purpose.

Ok thx. Just need root for ^^


Having upgraded my FP2 to FPOSOS I also avoided to re-install LibreSignal and BatteryFu. So I’m not polling internet 2 minutes every 3h anymone, but still locking the phone in 2G-only mode. And, surprise, the phone announce 7 days of battery life if the phone is not used.

I still have to confirm this “long-term” testing but it’s a hope.

Also, I noticed that I can’t switch the light on using Torchie (from F-Droid) anymore when phone is locked and screen is on. I only works when screen is on (wether phone is locked or not).

(and as a sided topic, I’m hoping for something to set notification LED blinking frequency)

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But it is not in flightmode but with activated 2G, right?
7 days WITHOUT using it still seems not very much, doesn’t it?
With FP1 I was used to 5 days WITH using it a little each day …

But please report back with some values after a longer testing period, also under your average using behaviour (and in comparison to your “before” state).

Just for a crosslink to another topic again recently discussed:
Cheers, Robert

Hard to gather meaningfull measurments. Currently, with phone usage (300 SMS a month, 5min of call by day) I experience 4 days of battery lasting.

I was using WaveUp, BatteryFu and some plugins to show CPU and Battery states. Removing all this allows the machine to be really idle when I’m not using it.

My normal state is : data disabled, and 2G only. Battery consumption curve shows that being idle is now energy-cheap, while turning screen on eats a lot and using 4G or WiFi or the main camera eats a lot more !

But I gained a safety feeling as I know it’s now not prone anymore to turn off when I’m not using it, so when I’m not noticing it for instance.

4 days, it’s enough not to have to plug the thing during w-e for instance…