I'm using Godox TT600 speedlites and adding the battery pack gives me 8 more AA cells to the 4 in the speedlite, so triple the life before recharging. When shooting with fresh Eneloop AA batteries in both the speedlite and battery pack, my speedlites are ready to fire again in less than 2 seconds. This does gradually fall off as the battery charge is used, but it's much better than working with just the 4 cells in the speedlite. I can work with them for several hours before fresh battery replacement becomes a "must do". This is for school senior type shoots where 3-5 shots at a time are taken and then there are spans of 5-15 minutes before the next group of shots are taken. I switch off the speedlites between these groups of shots, but can spend much of the afternoon doing this using just the first set of 12 Eneloop cells. My battery packs are JJC BP series from Amazon. The label doesn't say that it fits the Godox TT600, but it does. The label says it fits Canon CP-E4 / CP-E4N , but it does fit and work well with my Godox TT600 speedlites. I have 5 of these now. The Amazon page for them is amazon.com/gp/product/B01DQJ2G0I/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1 . The coil cord plugs into a standardized connector, so only this coil cord and the special speedlite connector end needs to change if a different speedlite connector is needed. I think JJC offers this same battery extender with different coil cords to fit many other brands and models of speedlites.
In use, this extender turns itself on and off when the speedlite is turned on and off. There are no switches on the extender, only a red LED in the top corner that shows when it is working. A bolt/knob is supplied with 1/4-20 threads for attaching it to the camera, tripod, etc. but I usually just ball bungee it to the light stand. The supplied nylon case has several means of allowing attachment, including a belt loop.
Charley
