If Cache size you are refering to is Video caching, then from everything I have read, that is amount of device memory used to store streamed videos in.
Which really should not be called Video caching. More like Video Storage Space.
Adjustable Cache generally uses a computing device's memory.
Number of batteries is irrelevant. Size of SD card for most part is irrelevant.
If you have a marginally slow SD card, then increasing Cache size may help.
Cache is used to help speed up data transfers between slower Input / Output devices and CPU(s).
There are different kinds of Cache.
L1 & L2 are typically part of core (CPU chip)
L3 usually sits between CPU and Memory, on separate chip.
Where things get confusing is some Memory has its own caching.
Similarily disk controllers can have their own caching and disk drives themselves can have caching.
If that isn't confusing enough, there is also Software caching that is part of Kernel or operating system.
With software caching being used to improve disk transfers speeds. Cutting down on repeat disk seeks for small chunks of data that may be scattered across a disk.
Some Operating systems allow user's applications to bypass Software caching.
As mentioned, the video cache is more a "streamed video store" on your phone at a lower resolution (720) and will suffer any breaks from signal loss, so it's handy but a poor second to the hi-def video recorded on your SD card on the drone itself.
If you have an Android phone with micro SD card, then you can choose to store the streamed video on your phone's SD card via the Go 4 App settings, and allow any size you like (I have mine set to 10 Gb I think)
If you have an I-Phone then you're stuck with it storing on the phone's internal storage and you probably want to keep it at 2-4 Gb depending on how much storage your phone has.
lvl.4
First Officer
