The one problem I have found with the Yongnuo 560iii is overheating. I dont think this is a problem with build/design of the flash just a consequence of the way I use it. I often mix this flash with studio flash and have the 560iii turned up to full power. According to the specs after 20 shots, the flash powers down to a 15 second recycling time. I assume buying an external power pack will solve this issue. Will it. I dont want to buy an external 8 AA battery bay - I would just end up managing huge numbers of AA batteries. So I am looking at external lithium packs which I think should work as the 560iii has a Canon battery pack socket. Does anyone use these? Do they work well? And what battery do they recommend? Isee that Godox have the 960 battery pack and there is another called a PB3000.