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The Cheetah 960 recycles two Canon 580 and 600 flashes at full power in one second, yes two flashes at the same time in one second. Quantum specifications say one second for full power on single speedlight flash.
Unless there is something of which I am unaware, fractional power recycling will be in general proportionally faster. I've not tested fractional power recycling since the flash is charged so fast, I just keep shooting.
When I use the PB820 (or Quantum 2x2 or Canon CP-E3), the limit to recycling is overheating of the Canon 600, not the battery "speed".
The Godox 820 is much like a Canon CP-E3 / E4, the 960 is more like a Turbo 3. All of the options reduce recycle time. The CP-E3 / E4 reduces charge time.
When I photograph a celebrity meet & greet, I typically go as fast as possible since the celebrity doesn't really want to do a long M&G, plus the time scheduled is fairly tight. Using a single Canon 600 at 1/4 to half power hits the overheating limit, so I'll use two or three flashes instead (with Canon, Godox, or Quantum battery packs). Most M&G's last 30 minutes and I'll take 2-3 exposures of each fan or fan group with the celebrity. 200 fans X 2.5 exposures = 500 flashes in 30 minutes. A single Canon 600 at 1/4 or more power does hit the overheat limit before the meet & greet is complete.
While it's good that the 600's are better at slowing and shutting off to prevent overheating, it also means one needs to be more aware than with 580's which kept going until they blew up .