Did you try the OS Monitor I linked? If it’s a software problem, this might help you find it.
I did try this a few times but saw no improvement. Is this likely a battery or software issue?
Battery behaves normally but when it gets below about 40% at some point it will rapidly lose charge and go to 0% in about 5 mins.
Sorry for the late reply. I’d say battery - I’ve had this on multiple devices once the battery gets older (in terms of the number of charge cycles, or in some cases for devices that typically are plugged into a charger most of the time). Replacing it made the problem go away, but obviously your mileage may vary.
1 Like
I bought a new battery, and i tried hardly to use this brand new one on the best way… and my FP still runs 7-8 hours before getting hungry… and if i try to use WiFi or 4G… it’s getting as hot as battery is getting empty… I’m quite upset right now. I don’t know how long my FP2 will stay in my pocket before being replaced by a “real” phone…
Sounds like a defective or bad software. Get in contact with for support!
While waiting for a response, you can try a factory reset. Or disable the phone and check that all modules are sitting right at their place.
To “Greenify”
I have used it for several months and was confident it would extend my batterie´s uptime per charge. One charge would either way last at least a day or more. But after some months as I did not even think of Greenifie´s background actions anymore my phone started very strange things. I had absolutely now clue how to fix it without performing a factory reset.
Before doing so after deinstalling all other additional apps which I have installed over the time there was nothing more left beside Greenify.
I simply could not imagine how the problem could be relates to this remaining third-party background app.
My phone had begun to run totally crazy after each reboot. I could use it for several seconds sometimes even minutes without having to unlock any of my two sim cards or even the phone itself. I could start apps and swipe screens. After some time then all unlock screens came up but my acoustic confirmation feedback was delayed just as my notification sound too. Furthermore it then took several seconds after unlocking to get back access to the phone again. Sometimes no icons or widgets were visible on any screen. It then was completely unusable for this session and needed rebooting again.
So at last I managed to also deinstall Greenify and after the next reboot all was fine again just as it should be.
This negative behaviour did not return after reinstalling the other apps without Greenify.
Relating to Firefox:
Each update may also introduce new bugs just as every other piece of software out there. This is typical and probably will never change as long as humans are programming software.
Anyway many apps offer the specific “quit” option in their menu. Firefox as explained in the docs then should completely close also clearing all private data as configured. This should finally close the app fully not remaining in the “running” apps list when also being closed on the overview screen afterwards.
Other apps or services from them may also need being “stopped” in the list of “running” apps and they may also need being “forced” to stop from within their individual app info screen.
This should prevent their services from restarting again while the main app wasn´t started manually.
I have this behaviour e.g. with the “Flic” app.
Also I have “ZXTune” installed. I have always wondered when the phone has automatically connected to the company´s car audio system via bluetooth that all of a sudden music was played although my main music app “MXplayer” was opened but remained paused not continuing the playback of the previous, completely different track.
To stop this behaviour I also forced ZXTune to stop (until it is intentionally started). Now my main music app interacts fine with the car audio system after reconnect.
“OS Monitor” looks nice and very informative. Still I miss the most important value to spot a battery drain. The actual current flow (monitor) while charging or discharging. Therefore I am using the “Ampere” app. It´s no replacement for a calibrated measuring device, but for a general overview it is totally fine.
For my judgement and experience every charging current above 500mA will do for FP2, up to 500mA though very slowly. USB 2.0 can only provide 500mA max. per socket. USB 3.0 does provide 900mA as stated by Wiki.
Depending on what apps are running and if there are any wireless connections active even 500mA could be too less for actual charging. It may only keep the phone up and running without actually increasing the battery level.
So the momentary power consumption level has to be overcome. The temperatur also takes influence in the battery drain.
Using an usb Y-cable or an external usb charging device with at least 1A (real current) output generally should be sufficient to charge FP2 at any time. It is proven that not all usb chargers actually provide the output as stated on their label. You can test if it works for your purpose or if someone is common with (calibrated) measuring devices simply perform live tests using proper equipment. Also there are ready-2-use usb test devices available for pass-through measurings.
A decent usb cable should not cause a too high voltage loss which depends on the used wire diameter (and lenght). This can make a differents whether most of the power comes to the device attached or too much power is lost by the cable and the attached device will charge too slow or not at all.
As FP2 is not designed for quick-charging (see “Does FP2 support Qualcomm QuickCharge 2.0? Hardware” thread), although the used Qualcomm cpu supports it there is no benefit of special quick-charging “data” cables or chargers. Any data cable (4 wires) will do if the wires used are of proper quality. Simple charging cables (2 wires) will do as well. To get quick-charging going a specific circuitry (in the cable or external charger) is needed activating the quick charge mode in the cpu.
*When charging FP2 with a simple 2 wire usb cable there should not be any difference when using a 4 wire cable as long as the wire specification does not differ. I could find usb cables passing currents through from about 350mA (nice looking flat/slim maybe coloured cable) up to the max. at about 1,3A with an ugly usual every day usb cable.
*Reedit for this point:
This statement I found to be true for external charging devices.
Using a PC usb output does make a difference here. A 2 wire usb charging cable can only provide power for this purpose and depends only on the cable quality.
A 4 wire usb cable (as often recommended) has also the two data lines connected which may cause the usb controller to decrease the current output and activate data syncronisation.
I could not experience any change depending on the selected “usb computer connection” mode beside “MTP” where charging was disabled for data transfer. Also the “charging” option did not increase the current level.
This behaviour can be checked with the battery status in settings->about phone->status “battery status” (Lollipop). Here you can see “charging over usb” or “charging over ac”.
AC should cause a higher charging current for faster charging (not to be mixed up with quick charge) with a decent cable (can reach ~1.3A). USB may be limited according to the max. specification of usb 2.0/3.0.
On 2 wires the phone cannot differ between any external charging device or a simple cable plugged into a pc usb port. Anyway it will switch to ac charging mode.
On 4 wires (which should most cables available be) it does recognise and the charging current may drop noticeably.
A Y-cable which is sometimes provided for external harddrives may bring a bit more current, but not necessarily (double) as at the end the same usb controller is waiting.
4 Likes
Thx a lot for that information and very thorough explanation.
I have the same issue… Phone becomes hot (above the battery) when I use the Internet (3G, 4G, wifi…) and drains very quickly.
But my phone is completely new !!
I did kickstart the battery, checked the SIM cards, the SD card, followed the battery guide, but nothing changes.
What should I do ? A 550€ phone which claimes to be “fair” but does now work properly is not quite “fair”…
How did you check them? How old are they?
I have one of my former operator (which doesn’t work anymore since I changed my operator some days after getting the fairphone) which is 2 years old, and did perfectly work in the previous phone, and another one from the new operator, which is totally new, that works perfectely in the previous phone I have kept.
With each one of the 2 SIM cards the fairphone overheats, but another phone works perfectly, so I think my SIM cards are not the problem.
I also tried with one card only in slot 1, with one card only in slot 2 : the phone still overheats and the battery drains quickly.
1 Like
For last couple of months CPU area of my phone got really hot when watching video, playing game or even some other kinds of apps. I think it was since some Fairphone open update (don’t remember the version).
After last update (Fairphone open 18.01.1) it got lot better. It never gets so hot and battery lasts longer.
3 Likes
A post was merged into an existing topic: 
Battery has short live, phone is overheating - La batterie se décharge vite, le téléphone chauffe trop
This week I suddenly had issues with short battery life. After using CPU Monitor Advanced Lite, an app which I can recommend if you want to find which app is using excessive CPU, I found that it was caused by F-Droid. The CPU usage was so few that the battery settings didn’t show F-Droid at all, but it caused frequent wake-ups at such a rate that I couldn’t make the end of the day on one charge which typically works fine even though my battery is slightly old and has occasional hiccups.
I don’t know why F-Droid had started using CPU excessively but after killing the process this morning, it stopped doing so.
Apps that you rarely use can cause a lot of trouble without you noticing! Last year, it was GMail, now it was F-Droid.
1 Like
In the settings of the F-Droid app I have the updates, automatic update interval to a week.
It could be that the setting on your phone was hourly.
1 Like
It’s set to daily. F-Droid did not appear to be using the network either when it woke up the CPU - usually it takes a while to download the package lists, so that should’ve been visible in the CPU monitor.
Anyway after killing its process the CPU usage vanished and I can’t reproduce it anymore. It was just a suggestion: check the hidden CPU usage of your apps when your battery is draining!
Hi. My fairphone 2 get suddenly really hot and drained battery in 2 hours.
I finally found the solution with FAQ of the website (Troubleshoot your Fairphone 2 issue --> Improve and monitor your battery life)
I restart on my phone on safe mode. Phone wasn t hot anymore, seems that it was an application problem.
Then I cleared all cache of the apps (Settings - Storage - tap Cached data - Clear cached data)
Since phone is working normally (hope for a long time 
5 Likes
I only now happened to stumble upon a possible malware problem, that can be responsible for battery draining as well as overheating the battery.
There are apps, that start mininig cryptocurrency (mostly monero) in the background. At a Kaspersky-Lab on battery caught fire, destroing the phone.
Mainly this threat comes by as an antivirus- or adult-content app. Pretending to be an antivirus app is a tad extra devious in my opinion. 
More info:
- Kaspersky Blog (2017-12-18): “Jack of all trades”
- Symantec Blog (2017-12-20): “Browser-Based Cryptocurrency Mining Makes Unexpected Return from the Dead”
- Avast Blog (2017-11-03): “Cryptocurrency mining malware sneaks onto Google Play”
- Trend Micro Blog (2017-10-30): “Coin Miner Mobile Malware Returns, Hits Google Play”
Might at least be worth looking into, if your phone suddenly unexpectedly starts draining the battery and turning hot.
2 Likes
Not a major factor for the extreme cases, but the Facebook app is very demanding on system resources and can cause overheating, reduce battery life and impair speed. I got rid of it, it’s better to use the web version instead.
FYI there are a few dedicated apps on F-droid that wrap the mobile web version and apply ad-blocking and custom CSS to it
1 Like