Filesystem for sdcard to store large file and apps access I am running android oreo 8.1 (custom ROM) on Xiaomi Redmi Note 3 Pro.  I have a 64GB memory card in which I want to store large files of size 15GB, 20GB etc. So I can't use FAT32 filesystem. 
I formatted it to exFAT but battery started draining faster as mount.exfat process uses CPU above 20-30% during read/write operation.

If I format to ext4, How can I made sdcard files available to all android apps ?
 Is there any other filesystem which can store large files and android apps can access it as well ?
I think your Micro SD card is not compitable with Android system try to use class 2 micro SD card sdhc(secure digital high capacity) type see if it's work. I do have same problem I have used 16GB Uhs-1 class 10 A1  (ultra high speed) micro SD card  but it's not compitable with the Android system it says can't read and Android system notify it's corrupted sd card, but soon after I try another micro SD card which is class 2 sdhc its work fine no countering any problem at all it's working  smooth when transferring data and fast rendering any apps I want to open that i have installed in my phone. There's so many type of micro SD card out there but need to see carefully some of it only suitable for hi digital camera which is usually using different file format system.