I also have huge problems charging my FP2.
I only have the phone for 1 month and previously I had not any problems charging it with either of my chargers or my computers. I think it started one or two days after the battery was totally uncharged.
Some days before the phone also fell down while being connected with a cable. This could have caused some mechanical stress to the contacts and/or to the whole phone.
When I plug in the charger cable it might start charging. I might be able make it charge by wiggling the cable. But after a while the charging light will go out eventually.
When I remove the battery and try again the phone might go into the endless loop of “Showing the Fairphone logo”, “vibrating”, “Turning off”.
Maybe there is a mechanical problem with the contacts. I tried several cables, chargers and phone positions but it seems to be random. Eventually the charging light will go out without me touching the phone or cable.
When I can get my phone to charge there might be another problem because the phone can get very hot and uncharge the battery. I tried to reset the battery as described here and this seems to have helped. But I had to re-do the resetting quite often. Sometimes it only charges for 5 to 10 minutes before I have to reset it again. The last two days I was able to charge my phone but it took the whole day because of the 1/2 hour waiting time recommended.
This obviously makes my phone unusable so I would be really appreciate some suggestions how to proceed.
Edit: It seems that charging works best when removing all SIM cards and the SD card and charging from the USB port of my computer. But this make the phone even more unusable because I cannot turn it on while charging and it takes longer to charge.
BTW: One of the SIM cards is quite old and I have cut it myself to make it fit. But this wasn’t a problem before and also this card works flawlessly on my other phone.