I'm looking for an external battery pack for my 600EX-RTs. I have found three that I think fit the bill:
From the specs, it appears that all of these units are capable of giving me the number of pops I need. So my main concerns are recharge time and battery life.
For recharge time, the Quantum and Lumedyne claim 1 second or less, while the Impact claims "1.0 - 3.5 seconds".
For battery life, the Lumedyne unit claims it is a "no-memory" battery pack, but doesn't specify the battery technology. The Quantum unit is NiMH, while the Impact unit is lithim ion.
I would appreciate hearing from anybody who has owned any of these units for an appreciable period of time.