Can a SD card slow your smartphone

Hi all! I'm having some problems currently with my Z5 Compact and SD card storage.


I used to have a Sandisk Extreme 32GB microSDHC card in my Z5C without problem for more than half a year. About a month ago, I wanted to replace it with a Sandisk Ultra 64GB microSDXC, and I am having extreme issues with speed and battery consumption whenever I try to use it.


Some examples: when the camera app is set to store photos and videos on the SD card, just starting the camera app sometimes takes ages. Taking and saving pictures is slow. In some instances, the rotating saving animation will show for around 20 seconds, and in the end the photo is still not stored on the card, and lost. Spotify is unbearably slow when its storage location is set to SD card. There is a 5-10 second pause almost every time I switch to another track, during which the app will seem to freeze, there's no information about the currently playing title, etc. Scrolling through playlists often freezes too, with all tracks showing as "Unknown title - Unknown artist - Unknown album", until everything loads about 10 seconds later. I also get regular messages like "Track ont available", "Go online to open menu", or "Storage not found", which all go away after a couple of seconds and things work again. Both of these apps, camera and Spotify, work fine again as soon as I switch them back to internal storage. They both worked fine using the old SD card.


The phone has generally become very slow, in some cases it takes almost half a minute to even unlock. It has also strongly affected battery life. A full charge is now usually empty about 3-5 times faster than without the SD card inserted, probably because all the SD reading and writing takes so much longer than it should.


A benchmark shows a sustained write rate of around 12 MB/s for the card, which is still in specification for a class 10 card. But I don't think the sustained speed is the problem, it seems to be random file access. For exapmle, one of the measures I tried taking is clearing Spotify's cache, which had grown to about 10 GB in 3,000 files. Because the cache clearing in app settings seemed to freeze, I went to delete the folder in File Commander. There, it showed that deleting each single file took about 2-3 seconds until it would delete the next one. So deleting Facebook cache took more than 3 hours and almost emptied an entire battery charge. If I format the SD card, it seems quick for about half a day to a day, until performance and battery life crash again.


At this point I'm not sure what the problem is. I have a few possible theories:

  • Might the specific SD card I have be defective, and could it work again if I just got it replaced?
  • Is the difference between Ultra/Extreme the problem? They both have the same speed class, but Extreme are advertised as faster, and about twice as expensive. My other Sandisk card, which was an Extreme, worked well, but I'm not sure if it is because of that. File access time is not advertised as a distinguishing feature.
  • Is the switch from 32 GB to 64 GB (and hence SDHC to SDXC) the issue? I.e., does the Z5C have any speed issues with SDXC cards, and should I just replace the card with an equivalent 32 GB model?
  • Should I go with an equivalent card from a different manufacturer? Would it be possible that that solves the problem?

I was hoping that maybe someone here has some insight from their own experiences with SD cards used in phones of the Z5 lines, maybe had the same problem at some point and has any pointers on what the possible cause is.