I am not sure what the problem is but I have had two SanDisk Ultra 32GB MicroSDHC Class 10 UHS fail on me after writing approximately 16 GB of data to them. I originally purchased one card from Amazon for use in an android netbook. I wrote about 7 GB of data to it with the android netbook and was able to read back all that I attempted to read (about 40% of what was written). After one day of use and no issues I inserted the card into a Kingston 19-in-1 USB 2.0 Flash Memory Card Reader (FCR-HS219/1) on a windows computer. I proceeded to write additional data to the card until i/o errors were reported and the file copy process failed. These errors began once the card was about 16GB full. I was unable to read or delete the file that only got partially copied. Refreshing the folder revealed a few dozen files and folders with corrupt file names (mostly characters not found on keyboard). Most files that had been copied to the card with the Kingston card reader before the errors were still accessible. I was unable to delete corrupt files and window’s check disk tool was unable to repair errors. I attempted to reformat the card using window’s format tool but it said “Windows was unable to complete the format.” I used the SD Association’s format tool which was able to reformat the card but the card remained unusable. Most files more than a few megabytes would fail to write. I tested the card in a windows laptop with built in SD card reader but all the same symptoms persisted. I concluded the card was defective and I returned it for a replacement card of the same kind.
Today I received the replacement card and immediately inserted it into my Kingston card reader and began copying files. Again, after approximately 16GB of data was written, i/o errors occurred and no more data could be copied. All files that were completely written to the card were still readable. As I did with the first card, I reformatted it with the SD Association format tool and tried writing data again. As before, file writing began failing within megabytes. I took the card to a second windows laptop with built in SD card reader (not the same laptop as mentioned before) and reformatted with the SD Association tool. Still the card failed to work properly.
The first card received had the text “4244CM00X023 BM MADE IN CHINA” etched on back.
The second card received had the text “4234PMA0N 2Z4 BM MADE IN TAIWAN” etched on back.
I have used my Kingston card reader for years with about 10 different cards and have had no prior problems. The two SanDisk microSD cards mentioned in this post were the first two with capacities greater than 16GB used in my card reader. My card reader continues to work properly with my older cards.
I can’t make sense of this. Is my luck so bad that I received two cards manufactured in two different countries that both had the same defect? Is my card reader defective or incompatible with these cards causing it to damage them so that they no longer work in other devices? Is SanDisk having a major problem with their manufacturing process?
I am looking for information because I don’t want to return a second card claiming it is defective until I know I am not making some correctable mistake.