I’m using FP1U and when at home, I have no problem getting through the day on one battery charge. I had previously noticed that it drains quicker when roaming, but over Christmas I spent 10 days in Spain and this time it was crazy. I found out that this is related to data roaming. When I leave data roaming on, the phone gets very hot and the battery drains really quickly (in a bit more than half a day). I then turned data roaming off and it was fine, but this is obviously not ideal!
Any idea what is causing this? Thanks 
Some questions:
- Which provider do you have (and which roaming partner do they have in Spain)?
- Did you stay in a city or in a rural area?
- Did you have GPRS, Edge or HSPA (G, E or H+ next to the connection symbol in the status bar)?
Hi Stefan, sorry, I was off the grid for two days!
- Provider: O2 Germany (Movistar in Spain)
- City (Bilbao)
- Mostly H+; I made sure it wasn’t because I was out of signal or something - signal in the area is generally very good.
I go there at least twice per year and this was definitely a new problem (last time was past July). Back then I noticed the battery was draining faster than at home, but nowhere near as fast as this time, and the phone was also not getting as hot. Is it possible that some app that relies on permanent connection (e.g. Facebook Messenger or something similar) is acting up when roaming? Aside from normal updates, downloading Facebook messenger is the only significant change I remember making since my last trip to Spain.
No problem! 
Yeah, since you stay in a city, battery consumption should be lower than on the countryside.
Hm, I could imagine that Facebook Messenger, if it is polling (looking for new messages constantly), would eat up a lot of battery.
You could see, if it’s Facebook Messenger if you disable/uninstall it, when you are in Spain the next time. Other than that, I don’t really see how to get to the root of this, unfortunately… 
Thanks Stefan! I will give uninstalling Facebook messenger a shot next time (I hate it anyway, but the other day I needed it for something so I finally caved). Otherwise… anyone else with the same problem or an idea what might be causing this?
You don’t have to miss out because there are other apps, which provide a Facebook chat: Tinfoil for Facebook from F-Droid is recommended because it doesn’t let Facebook access your data. On the other hand it is basically the mobile Facebook page, so the user experience might not be as good as with the native Facebook apps.
I had this crazy battery drain in october when I was in Barcelona (German SIM from Congstar, roaming in Movistar network and Spanish SIM from Yoigo). Normally, it works fine there, but during some days, it drained so quickly, that I ordered a new battery, because I thought mine was dying. Then, the day I paid the new battery, suddently everything went fine again. Maybe Movistar are making ajustments to their network and this is what provokes the drains…??