I agree with Ben.  Powerful CPU can do it very quickly but will draw a lot of power.  My experience is similar. 

For any SD card I always use the SD Card Association's formatter utility first as it removes any partitions or any other weird formatting (bootable flags, etc)
https://www.sdcard.org/downloads/formatter/

Next, this free program has always worked well for me on any media windows can assign a drive letter to.
http://ridgecrop.co.uk/index.htm?guiformat.htm
It without fail makes any media into FAT32

After a few hiccups(crashes) on other formats, I just used handbrake to convert all my desired videos into MP4 files before converting.  I made the dimensions scaled or cropped to multiples of 16 and changed the framerates to standard 24 or 30 fps depending on the source. 

I spent some time re-encoding & converting a little over 100 retro-game related video clips into TSV format 18GB altogether.
90's videogame commercials, gameplay clips, etc.  Figured I'd share them.
https://anapan.ca/Anapan/TinyTV/
You can preview the clips in your browser by going into the subdirectories at the top, or download them all as a 3.7gb by downloading the file 0_ALL_TSV.7z

Love this product and look forward to building the new one(s).