For photographers who need longer battery life with Speedlite flashes, the standard has been very expensive Quantum battery packs. Typically around $300+ dollars (seen here via B&H). There are a few cheap external solutions that use 6x AA batteries (seen here on eBay), but they are merely extended power sources and often don't help to improve recycle times.
Now a popular product making rounds in the last year as an alternative is the GoDox external flash battery packs. GoDox also have a variety of other lighting products including large studio strobes and continuous lights. I had a brief look at these products over at the PhotoPlus Expo in New York, and these battery packs look very good. The Godox external flash battery packs are available for Canon, Nikon, and popular Yongnuo flashes as well found via eBay (Click here).
GoDox External Battery Packs for Canon Nikon Yongnuo Flashes
Strobist: Canon 5D Mark II + Canon 24-105mm IS F/6.3, 1/125th, ISO 200, Single 580 EX II (set to manual mode) Shot through White Umbrella - Camera Left. No HSS, triggered with ST-E2, Exposure Controlled by Fader ND filter.
My neighbor often sees me running around the front of my house chasing my kids around with my camera. He asked if I can take a few snaps of his daughter. I don't think he really knew quite my investment and experience in photography. It was about 12 noon on a super duper bright sunny day. In order to expose for the sky without maxing out my shutter speed and keeping some DOF, I threw on the Fader Filter ND. It was important for me to keep my shutter down under 1/250ths of a second. Forgive some of the shots, this is her first time in front of a camera, and she's only 13. We started in the studio (my living room), to get her a bit comfortable, then took it outdoors. I think she might have been a bit intimidated by all the equipment and assistants I had with me also.
Why not use High Speed Sync?
With a single 580 EX II, shooting through an umbrella, I wanted to use the maximum power output of my 1 flash. When going into HSS mode, the flash needs to pulse which reduces the power output. So by keeping my shutter speed to normal sync speed, I was able to use the full burst power. In actuality I only needed between 1/8th and 1/4 power. Staying at fractions of full power allows me to have super fast recycle times too.
Threw my subject into a shaded area to balance lighting, under exposed the sky using a Fader ND, and then filled my subject with a single 580 EX II off camera, shot through a White Umbrella, triggered by a Canon ST-E2. Very simple, portable, cheap, yet effective way to get quality fill flash outdoors. This method allows you to use any flash since the sync speed is below HSS needs. Too bad I didn't have someone shooting some BTS video, this would have been a great tutorial to share.