When Sony's A99ii Full Frame DSLT camera came out it had leading specs that people like me drooled over. But unfortunately it seems that Sony never intended pros to use this camera's 4K video recording for more than a minute of video. I guess they want us to fork out the big bucks for a dedicated Video Camera, rather than have the novelty of an all in one Photo / Video machine. After several years I think I have found the cause of the overheating, and its all in the batteries.
Of course nobody wants to fork out $60 per OEM Sony NP-FM500H battery. So we all rush to ebay or amazon and buy the over rated generics. And for the most part they work. When just taking photos, the generics work just fine. And in my experience brand new generic batteries even work great for 4K video recording. But after you have run them through the charger a few times, it seems they start to act up. If you go to charge them and it seems that the final last bit of charge takes forever, even days until the charger thinks they are charged, that could be a sign of the battery starting to go bad. Either that or my charger is over charging them.
If the batteries are over charged, and pushing a slightly higher voltage through the camera, this naturally will cause things to run hot. And when you do something demanding like record 4K video, the internal temperature of your camera is going to increase with that higher voltage.
This has happend to me several times. What I find amazing is switching to a different set of batteries sometimes fixes the issue. Sometimes the other set of batteries is even worse. I will admin to being a battery whore, and refuse to throw away old batteries. So my camera bag has about 2 dozen NP-FM500H batteries all of different brands and ages.
So next time your camera overheats during 4K video recording try some new batteries.
So in a few weeks I have to do some video work. The last thing I want is my camera over heating in the middle of a shoot. So I bought a brand new pair of Wasabi generic Batteries NP-FM500H. I charged them, then put them in my Sony A99ii, then ran a little test. I setup my camera on a stand and enabled 4k Video recording using the same settings ( ISO 1600, Manual Mode, 4K, 100mbit 30fps ) that I use at my client's. I started recording. My goal was to see how long it would take til it overheated and crashed.
Well I am at over 18 minutes, and still no overheating indicator. I picked up the camera and felt a little heat coming off where my right thumb would rest, and the right side of the camera, but much less than I have experienced using other batteries. At this point I am pretty sure the overheating issue is with batteries and no so much the camera.