Never heard of that. They can get warm when you're pulling a lot of power from them and ambient heat from the atty can add to this, but I've always assumed that this was acceptable so long as they're not getting HOT. If you can still hold them in your hands and they're not feeling ridiculously warm, then you're probably aright. They can handle modest amounts of heat under discharge.
Honestly, when I had them, I pushed my VTC5's somewhat close to their current limit and I noticed that they tended not to get quite as toasty as my Samsungs or LG's.
Now when they're charging, yes, you absolutely need to make sure that they're cool before you stick them on a charger. Also of course ensure that they're not getting warm when charging.
I think finding real VTC5's is gonna be hard these days. I'm not even convinced that they're still being made atm. VTC4's are easy enough to find though, and they're still some of the best batteries you can buy.
The VTC5 is a 20 amp continuous cell.
Huh? They are 30 amp cells, not 20. The only difference between them and the VTC4's are 500 extra mah's and a little extra internal resistance.
Edit: Well, maybe it IS actually a 20a battery. I never actually looked a the discharge curve. I just found this interesting little reddit thread:
https://www.reddit.com/r/electronic..._venerable_sony_vtc5_is_it_really_a_30a_cell/
Very interesting...
Either way, I imagine heat wouldn't be much of an issue at around 20 amps. Stay at or under that and you should be alright.